Research ArticlePrediction of Unconfined Compression Strength forSaline-Alkaline Soils Mixed with Cement and Wheat Straw

Guoqi Xing Changjiang Liu Wei Xuan Yueyue Pan Bing Zhang and Yue Zhao

College of Architectural Engineering Weifang University Weifang Shandong China

Correspondence should be addressed to Guoqi Xing xgq1105163com

Received 22 January 2020 Revised 27 March 2020 Accepted 3 April 2020 Published 21 April 2020

Academic Editor Akbar Heidarzadeh

Copyright copy 2020 Guoqi Xing et al -is is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

A series of unconfined compression tests were performed to investigate the influence of wheat straws on the unconfinedcompression strength for saline-alkaline soils and saline-alkaline soils mixed with cement In unconfined compression tests 20groups of soil specimens were prepared at five different percentages of wheat straws content (ie 00 01 015 02 and025 by weight of saline-alkaline soils) and four different percentages of cement content (ie 0 3 6 and 9 by weight ofsaline-alkaline soils) and unconfined compression tests were carried out after 3- 7- 14- 28- and 56-day curing periods Testresults indicated that the inclusion of wheat straws within saline-alkaline soils and saline-alkaline soils mixed with cement leads toan increase in the unconfined compressive strength of specimens and also changed the brittle behavior to a more ductile one forspecimens In addition based on the results from unconfined compression tests a formula for predicting the unconfinedcompression strength of specimens related to cement content wheat straw content curing periods etc was determined andcomparing with the results from unconfined compression tests it had higher precision in predicting the unconfined compressionstrength of specimens

1 Introduction

Due to many advantages of synthetic fibre such as highstrength and fairly good corrosion resistance it is widelyused in the reinforcement of weak or soft soil and someresearchers had studied the mechanical properties of the soilmixed with synthetic fibre [1ndash5] Now the applied tech-nology for the soil reinforced with synthetic fibre is widelyused in geotechnical engineering In addition natural fibreincluding plant fibre such as wheat straw rice strawbamboo and ditch reed also attracts general attention dueto the advantages of easy degradation lower cost beingenvironment-friendly and so forth Some researchers hadalso carried out feasibility study on the soil reinforced withnature fibre [6ndash8] and the results showed that the strengthof soil could be effectively improved by adding natural fibre[9ndash12]

Saline-alkaline soils are widely existent in west coast ofBohai Bay and southeast coast in China -e salt content isgreater than 03 in saline-alkaline soils which can make

the subgrade expanded Moreover the saline-alkaline soilscan also make the pavement collapse -erefore the saline-alkaline soils cannot directly be used as roadbed filling andthen cement or lime is often used in reinforcing the saline-alkaline soils In order to apply saline-alkaline soils to thegeotechnical engineering some researchers had alreadyinvestigated the mechanical property of saline-alkaline soilsreinforced with cement or lime [13ndash15]

In northern China a large number of wheat straws areburned or piled up on the open-air causing environmentalpollution Wheat straws used as reinforced materials aredifferent from rigid materials such as soil nailing andanchor bar and flexible materials such as geotextile inmechanical properties-e main advantage of wheat strawsis that they are locally available and very cheap If wheatstraws are used in soil reinforcement they are biode-gradable and thus do not create disposal problems in theenvironment Wei et al [16] explored the tensility of wheatstraw based on test method In addition some researchershad already applied the wheat straws as reinforced material

HindawiAdvances in Materials Science and EngineeringVolume 2020 Article ID 2765145 14 pageshttpsdoiorg10115520202765145

to soft soil or saline-alkaline soils [17ndash22] However up tonow the theories for the soil reinforced with wheat strawsare still in primary stage and should be further studied

-erefore in this paper the effect of wheat straws onthe saline-alkaline soils is further studied supplementingthe data available in the literature on the behavior of fibre-reinforced soil Firstly a series of unconfined compressiontests are carried out to explore the effect of wheat straws onsaline-alkaline soils Secondly based on the data obtainedfrom unconfined compression tests a formula for pre-dicting the unconfined compression strength of saline-alkaline soils mixed with cement and wheat straws is de-rived accurately

2 Materials and Experimental Program

21 Materials Saline-alkaline soils samples used in the testsare obtained from the west coast of Bohai Bay China -emicrostructure for saline-alkaline soils obtained from SEMtest is shown in Figure 1 showing the flocculated structure insaline-alkaline soils In order to mould the saline-alkalinesoils in the laboratory firstly they are dried in air and thenbroken into pieces -e physical properties and ion contentfor saline-alkaline soils are listed in Tables 1 and 2 re-spectively As shown in Table 1 for the saline-alkaline soilsused in test they are silty clay based on the classification ofthe soil [23] As can be seen from Table 2 the content forCO3

minus 2 and HCO3minus in 1000 g soils is 0382mmolkg which isgreater than 03mmolkg (JTG D30-2015 [24] nationalcriterion for highway subgrade in China) and so the soil iscalled saline-alkaline soil In addition the ordinary Portlandcement is used as the reinforcement material and thechemical content and physical properties for ordinaryPortland cement are listed in Table 3

-e wheat straws used in test are obtained from HantingDistrict China Before wheat straws are mixed into soilsthey should be split into strips as shown in Figure 2 InFigure 2 the mean width and mean length for the strips areabout 15mm and about 10mm respectively -e crosssection of wheat straw is shown in Figure 3 showing that thefibre tissues are loose and suitable for humectation diffu-sion and permeation of liquid In order to prevent wheatstraws from decay in saline-alkaline soils they should besoaked in limewater with 04 lime by weight of water for24 h and then are dried in air [20]

22 Specimen Preparation In unconfined compressive testspecimens with 391mm diameter and 80mm height areused as shown in Figure 4 In this paper the content ofwheat straw and cement is defined as

Ww Tw

T (1)

Wc Tc

T (2)

where Tw is the weight of wheat straw Tc is the weight ofcement and T is the weight of air-dried saline-alkaline soilsIn test the value of Wc is adopted as 0 003 006 and 009

and Ww is adopted as 0 0001 00015 0002 and 00025Based on the values ofWwWc and T the required weight ofwheat straw and cement can be calculated using equations(1) and (2)

Before mixtures are poured into mould the inside of themould should be coated with lubricant which can reduce thefracture of specimens during removal In preparing thespecimens the mixtures of saline-alkaline soils cement andwheat straw should be divided into three equal portions andthen each portion pours into the mould to be compacteduntil reaching maximum dry density with optimum mois-ture content Between each compression layer the surface ofcompression layer should be scoured providing reasonablebonding between compression layers In addition if cementand wheat straw are not used in specimens air-dried saline-alkaline soils are mixed with water based on optimummoisture content If cement is used only in specimens re-quired water is first poured into air-dried saline-alkalinesoils considering quick hydration of cement and then ce-ment is added to moist saline-alkaline soils If wheat strawsare used only in specimens they are firstly added to air-driedsaline-alkaline soils to achieve uniform mixtures and thenrequired water is added to mixture of wheat straws andsaline-alkaline soils If cement and wheat straws are all usedin specimens moist mixtures of wheat straws and saline-alkaline soils are firstly prepared as described above andthen cement is added to the moist mixture At each stage ofmixing mentioned above homogeneous mixtures are pre-pared manually After all specimens are compacted inmould they should be wrapped with plastic membrane andthen placed in curing chamber for 3 7 14 28 and 56 daysrespectively

In this study 20 groups of specimens mixed with dif-ferent cement content and wheat straw content are preparedfor the unconfined compression tests (GBT 50123-1999[25] which is the national criterion for geotechnical tests inChina) In order to ensure the repeatability of experimentsverification tests should also be carried out and thereforeeach group should include 3 specimens -e details ofdifferent cement and wheat straw content are shown inTable 4 Moreover for the specimens used in tests they

20μm EHT = 500kVWD = 76mm

Signal A = SE2Mag = 300X

Date 27 Nov 2019Time 100829

Figure 1 Microstructure of saline-alkaline soils

2 Advances in Materials Science and Engineering

should be in the state of maximum density which can beobtained from compaction tests Table 4 also shows theoptimum moisture content for each group

Table 3 Chemical content and physical properties of ordinary Portland cement

SiO2 Al2O3 Fe2O3 CaO MgO SO3 LOI Specific surface Compressive strength (28 days)223 46 36 653 29 38 17 373m2kg 448MPa

Figure 2 Wheat straws used in test

100μm EHT = 500kVWD = 72mm

Signal A = SE2Mag = 150X

Date 27 Nov 2019Time 103601

Figure 3 Cross section of wheat straw

Table 1 Basic mechanical properties for saline-alkaline soils

Specificgravity Gs

Consistency index Compaction test Grain contentLiquid limit

wL ()Plastic limit

wp ()Plasticindex IP

Maximum drydensity ρd (gmiddotcmminus3)

Optimum watercontent s ()

0074sim0038(mm)

0038sim0008(mm)

lt0008(mm)

271 325 169 156 185 168 225 573 211

Table 2 Ion content in saline-alkaline soils g

CO3minus 2 HCO3

minus CIminus SO42minus Ca2+ Mg2+ K+ +Na+ PH value Content of soluble salt

0019 0171 18011 0871 0369 0761 9931 772 332lowast-e ion content is the ion mass in 1000 g saline-alkaline soils

Figure 4 Specimens for unconfined compressive test

Table 4 Cement and wheat straw content and optimum moisturecontent in specimens

Specimenno

Cementcontent ()

Wheat strawcontent ()

Optimum moisturecontent ()

S 0 0 127W 1 0 010 129W 2 0 015 129W 3 0 020 131W 4 0 025 131C 1 3 0 130C 2 6 0 135C 3 9 0 139CW 1 3 010 131CW 2 3 015 131CW 3 3 020 133CW 4 3 025 133CW 5 6 010 138CW 6 6 015 138CW 7 6 020 141CW 8 6 025 141CW 9 9 010 143CW 10 9 015 143CW 11 9 020 145CW 12 9 025 145

Advances in Materials Science and Engineering 3

23 Unconfined Compression Tests In order to obtain un-confined compression strength of specimens conventionalunconfined compression apparatus is used in test as shownin Figure 5 In the unconfined compression test axial forceand corresponding displacement can be obtained auto-matically with multichannel real-time record system Inaddition unconfined compression tests are carried out at thelast day of curing period for specimens For the conventionalunconfined compression apparatus used in test the loadingrate is set to be 24mmmin until specimens failed

3 Results and Discussions

31 Effect of Wheat Straws on Unconfined CompressiveStrength of Specimens In this paper based on the resultsfrom unconfined compressive tests on specimens mixedwith cement and wheat straws after curing for 14 days thestress-strain curves are obtained as shown in Figures 6(a)ndash6(c) As can be seen from Figure 6(a) with increasing wheatstraw content unconfined compressive strength of speci-mens also increases However further increase of wheatstraw content does not significantly improve the peak axialstress Furthermore specimens mixed with increasing wheatstraw content exhibit more ductile behavior than that notmixed with wheat straws Figure 6(b) shows the influence ofcement content on unconfined compressive strength ofspecimens As can be seen from Figure 6(b) increasingcement content can improve the peak axial stress of spec-imens andmeanwhile exhibit more brittle behavior than thatnot mixed with cement Figure 6(c) shows the influence ofwheat straw content on unconfined compressive strength ofspecimens mixed with cement As can be seen fromFigure 6(c) when the cement content is constant in spec-imens the influence of increasing wheat straw content onunconfined compressive strength of specimens is similar tothat in Figure 6(a)

-e influence of wheat straw content on unconfinedcompressive strength of specimens mixed with differentcement content after curing for 14 days is shown in Figure 7As can be seen from Figure 7 not only for cementedspecimens but also for uncemented specimens the addedwheat straws can increase unconfined compressive strengthof specimens As shown in Figure 7 after 01 wheat strawswere added unconfined compressive strength of specimensreinforced with 3 6 and 9 cement content increasesfrom 018 to 022MPa from 036 to 040MPa and from 051to 053MPa respectively showing that added 01 wheatstraws content has little effect on the improvement of un-confined compressive strength of specimens However after025 wheat straws content is added unconfined com-pressive strength of specimens reinforced with 3 6 and9 cement content increases from 019 to 038MPa from036 to 052MPa and from 049 to 058MPa respectively

-e influence of curing periods on unconfined com-pressive strength of specimens mixed with 3 cementcontent and 01 wheat straw content is shown in Figure 8As can be seen from Figure 8 unconfined compressivestrength of specimens increases with curing periods Inaddition when curing periods are less than 14 days the

failure of specimens exhibits the ductile behavior Howeverwhen curing periods are greater than 14 days the brittlebehavior of failure of specimens becomes more and moreobvious

32 Effect of Wheat Straw Content on Failure Mechanism ofSpecimens In this section the specimens after curing for 28days are used in unconfined compressive strength testFigures 9(a)ndash9(e) show the failure of specimens only mixedwith wheat straws As can be seen from Figure 9(a) whenwheat straws are not added to specimen the failure occursmainly on the bottom of specimens showing the shearfailure mode When the wheat straw content is 010 byweight the failure also occurs mainly on the bottom ofspecimens however the shear plane does not form asshown in Figure 9(b) When the wheat straw content isincreased to 015 by weight a large shear plane formswhich extends to the top of specimens as shown inFigure 9(c) As can be seen from Figure 9(d) when the wheatstraw content is increased to 020 by weight there are twofailure modes in specimens one shear failure and anotherbottom failure of specimens When the wheat straw contentis increased to 025 by weight the bottom failure inspecimens only occurs and shear plane does not form asshown in Figure 9(e)

Figures 10(a)ndash10(e) show the failure of specimens mixedwith different wheat straws content and 6 cement contentWhen wheat straws are not added in the specimens the shearplane failure is mainly exhibited which also shows the brittlebehavior of specimens as shown in Figure 10(a) Howeverwhen wheat straws are added in the specimens and the wheatstraw content reaches 010 and 015 by weight a largeshear plane forms in specimens as shown in Figures 10(b)and 10(c) As can be seen from Figure 10(d) when the wheatstraw content is 020 by weight only the bottom failure ofspecimens is shown and shear plane does not form Howeverthe top failure of specimens occurs when the wheat strawcontent reaches 025 by weight and also shear plane does notform in specimens as shown in Figure 10(e)

Based on the results of unconfined compressive strengthtests on specimens mixed with 3 cement content and 01wheat straw content the effect of curing periods on thefailure of specimens can be obtained as shown inFigures 11(a)ndash11(e) As can be seen from Figures 11(a) and11(b) when the curing period is less than 7 days the failure

Figure 5 Unconfined compression apparatus

4 Advances in Materials Science and Engineering

of the bottom of specimens occurs and it does not obviouslyexhibit the shear plane When the curing period is 14 daysthere are two simultaneous failure modes in specimens asshown in Figure 11(c) However as can be seen fromFigures 11(d) and 11(e) when the curing period is greaterthan 14 days only shear plane failure occurs in specimensDuring the unconfined compressive strength tests we alsofind that the increasing of curing periods can improve thebrittle behavior of specimens and the trend for influence ofcuring periods on the brittle behavior of specimens is similarto that shown in Figure 8

33 Prediction for Unconfined Compressive Strength ofSpecimens Mixed with Wheat Straws and Cement As

discussed above the factors affecting unconfined com-pressive strength of specimens include wheat straw contentcement content and curing periods In this section a for-mula that can predict unconfined compressive strength ofspecimens is put forward based on the results from un-confined compressive strength test on saline-alkaline soilsmixed with wheat straws and cement Figures 12(a)ndash12(d)show the increasing of unconfined compressive strength ofspecimens with curing periods

As can be seen from Figures 12(a)ndash12(d) when thespecimens have the same cement content unconfinedcompressive strength of specimen increases with increasingwheat straw content Based on the data from Figures 12(a)ndash12(d) the curve fitting for the relationship between curingperiod and unconfined compressive strength of specimens

00 10 20 30 40 50 60 70 80 90000

002

004

006

008

010

012

014

016

Axial strain ε ()

Axi

al st

ress

σ (M

Pa)

0 wheat straw010 wheat straw 015 wheat straw

020 wheat straw025 wheat straw

(a)

00 10 20 30 40 50 60 70Axial strain ε ()

00

01

02

03

04

05

06

Axi

al st

ress

σ (M

Pa)

00 cement30 cement

60 cement90 cement

(b)

00 10 20 30 40 50 60Axial strain ε ()

00

01

02

03

04

05

06

Axi

al st

ress

σ (M

Pa)

0 wheat straw + 6 cement010 wheat straw + 6 cement 015 wheat straw + 6 cement 020 wheat straw + 6 cement025 wheat straw + 6 cement

(c)

Figure 6 Stress-strain curves of specimens after 14-day curing period (a) Specimens mixed with different wheat straw content (b)Specimens mixed with different cement content (c) Specimens mixed with 6 cement content and different wheat straw content

Advances in Materials Science and Engineering 5

005 010 025020 030000 015Wheat straw content ()

01

02

03

04

05

06

07

08

Axi

al st

ress

σ (M

Pa)

0 cement3 cement

6 cement9 cement

Figure 7 Relationship between wheat straw content and unconfined compressive strength after curing for 14 days

0000 0005 0010 0015 0020 0025 0030 0035 004000

01

02

03

04

05

06

Axi

al st

ress

σ (M

Pa)

Axial strain ε ()

3 days7 days14 days

28 days56 days

Figure 8 Influence of curing periods on unconfined compressive strength of specimens

(a) (b) (c) (d) (e)

Figure 9 Effect of wheat straw content on failure mechanism of specimens (a) 0 wheat straw content (b) 010 wheat straw content (c)015 wheat straw content (d) 020 wheat straw content (e) 025 wheat straw content

6 Advances in Materials Science and Engineering

mixed with 02 wheat straw content and different cementcontent is shown in Figures 13(a)ndash13(d)

In Figures 13(a)ndash13(d) the curve fitting can be expressedby the following expression

p pu minus p0( 1113857 middot 1 minus e(minus αmiddott)

1113872 1113873 + p0 (3)

where p is unconfined compressive strength of specimens tis curing period pu is ultimate unconfined compressivestrength p0 is initial unconfined compressive strength α isthe coefficient related to the shape of curves

In equation (3) using fitting method pu p0 and α canbe obtained based on the data from Figures 12(a)ndash12(d) asshown in Table 5

As shown in Table 5 α is in the range of 014398 to014643 showing that the change of the value of α is verylittle -e mean value for α is 014533 -erefore in order tosimplify equation (1) the value of α is replaced by 0145 andequation (1) can be expressed as

p pu minus p0( 1113857 middot 1 minus e(minus 0145middott)

1113872 1113873 + p0 (4)

331 Initial Unconfined Compressive Strength p0 Inequation (4) p0 and pu can also be obtained based on the datafrom Figures 10(a)ndash10(d) by fitting method as shown inTable 6 Based on the data fromTable 6 the curve fitting for therelationship between p0 and wheat straw content for differentcement content can be obtained as shown in Figure 14

For the curve fitting in Figures 14(a)ndash14(d) it can bedescribed by the following expression

p0 η middot ebmiddotas + p0i (5)

where η is the coefficient for curve growth as is wheatstraw content b is the exponent p0i is initial uncon-fined compressive strength only related to cement con-tent Based on the data from Table 6 η b and p0i inequation (5) can be obtained by fitting method as shownin Table 7

As can be seen from Table 7 the change of η is very littleand the mean value for η is 00017 -erefore equation (5)can be simplified and expressed as

p0 00017 middot ebmiddotas + p0i (6)

Similarly based on the data from Table 6 and equation(6) b and p0i can be obtained by fitting method as shown inTable 8

As shown in Table 8 the change of b is also very little andthe mean value for b is 9356 -erefore in order to simplifyequation (6) b is replaced by 9356 in equation (6) and thenit is expressed as

p0 00017 middot e9356middotas + p0i (7)

Moreover as can be seen from Table 8 p0i is related tocement content Based on the data from Table 8 the rela-tionship between p0i and cement content can also be ob-tained as shown in Figure 15

(a) (b) (c) (d) (e)

Figure 10 Effect of wheat straw content on failure mechanism of specimens mixed with 6 cement content (a) 0 wheat straw content (b)010 wheat straw content (c) 015 wheat straw content (d) 020 wheat straw content (e) 025 wheat straw content

(a) (b) (c) (d) (e)

Figure 11 Effect of curing period on failure mechanism of specimens mixed with 3 cement content and 01 wheat straw content (a) 3days (b) 7 days (c) 14 days (d) 28 days (e) 56 days

Advances in Materials Science and Engineering 7

-e curve fitting for relationship between p0i and cementcontent in Figure 15 can be expressed as

p0i 008014 + 001086 middot ac (8)

where ac is cement content -erefore equation (7) canbe expressed as

p0 00017 middot e9356middotas + 001086 middot ac + 008014 (9)

332 Ultimate Unconfined Compressive Strength pu In thissection equation (4) is also used to determine the value of puHowever in equation (4)p0 can be obtained from equation (9)

according to the cement content and wheat straw contentFurthermore based on the data from Figures 12(a)ndash12(d) pucan be obtained with equation (3) as shown in Table 9

For the curve fitting in Figure 16 it can be described bythe following expression

pu a middot eminus ςmiddotas( ) + pui (10)

where a is the coefficient related to curve growth as is wheatstraw content b is the exponent pui is initial ultimateunconfined compressive strength of specimens only relatedto cement content Similarly a ς and pui in equation (10)can be obtained by fitting method based on the data fromTable 9 as shown in Table 10

0 10 20 30 40 50 60 7000

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing age (day)

0 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(a)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing age (day)

3 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(b)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing age (day)

6 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(c)

00

01

02

03

04

05

06

07Pe

ak st

ress

σ (M

Pa)

0 10 20 30 40 50 60 70Curing age (day)

9 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(d)

Figure 12 Effect of curing periods on unconfined compressive strength of specimens mixed with wheat straws and different cementcontent (a) 0 cement content (b) 3 cement content (c) 6 cement content (d) 9 cement content

8 Advances in Materials Science and Engineering

0 10 20 30 40 50 60 7000

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing aging (day)

0 cement content

(a)

000 10 20 30 40 50 60 70

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing aging (day)

3 cement content

(b)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing aging (day)

6 cement content

(c)

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing aging (day)

9 cement content

(d)

Figure 13 Curve fitting for the relationship between curing periods and unconfined compressive strength of specimens mixed with 02wheat straw and different cement content (a) 0 cement content (b) 3 cement content (c) 6 cement content (d) 9 cement content

Table 5 pu p0 and α in equation (3) obtained by fitting method

Cement content () Wheat straw content () A pu p0 Correlation coefficient (R)

0

000 014588 043154 009152 098592010 014516 044304 009313 098594015 014618 044932 009624 098513020 014544 045447 010006 098573025 014475 046229 010691 098532

3

000 014579 058251 012124 098826010 014551 058510 012383 098837015 014540 058738 012611 098756020 014464 059306 013179 098620025 014476 059871 013744 098922

6

000 014398 073439 015303 098871010 014613 073703 015567 098887015 014558 074029 015893 098998020 014623 074398 016262 098928025 014489 074994 016858 099096

9

000 014483 089900 018327 099765010 014643 090140 018567 099796015 014568 090410 018837 099796020 014456 090841 019268 099864025 014483 091405 019832 099801

Advances in Materials Science and Engineering 9

Table 6 p0 and pu in equation (4) obtained by fitting method

Cement content () Wheat straw content () α pu p0 Correlation coefficient (R)

0

000

0145

042040 008205 098389010 043203 008498 098396015 043892 008708 098338020 044639 009132 098464025 045536 009759 098451

3

000

0145

056306 011459 098765010 057668 011623 098763015 058741 011906 098752020 059589 012309 098607025 061033 012917 098894

6

000

0145

075501 014632 098870010 075883 014825 098885015 076059 015161 098966020 076642 015566 098839025 078146 016166 099062

9

000

0145

093233 018034 099679010 094507 018203 099703015 095207 018589 099711020 095780 018931 099748025 096357 019594 099705

000

002

004

006

008

010

012

014

016

018

020

022

024

026

0080

0085

0090

0095

0100

P 0 (M

Pa)

Wheat straw content as ()

0 cement content

(a)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0110

0115

0120

0125

0130

3 cement content

(b)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0140

0145

0150

0155

0160

0165

0170

6 cement content

(c)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0175

0180

0185

0190

0195

0200

9 cement content

(d)

Figure 14 Curve fitting for the relationship between p0 and wheat straw content for different cement content (a) 0 cement content (b)3 cement content (c) 6 cement content (d) 9 cement content

10 Advances in Materials Science and Engineering

As can be seen from Table 10 a is in the range of 000832to 000861 showing that the change of a is very little -emean value for a is 000849 and the value of a in equation(10) is replaced by 00085 then equation (10) can beexpressed as

pu 00085 middot eminus ξmiddotas( ) + pui (11)

-en based on equation (11) and the data in Table 9 ςand pui can be further obtained by fitting method as shownin Table 11

Figure 17 shows the curve fitting for the relationshipbetween ξ and cement content and the following expressioncan describe the curve fitting

ξ a1 middot eminus b1 middotac( ) + ξ0 (12)

where a1 is the coefficient related to curve growth ac iscement content b1 is the exponent ξ0 is initial value of ξonly related to cement content Based on the data fromTable 11 a1 b1 and ξ0 can be obtained by fitting methodwhich are 1514 0096 and 5002 respectively -ereforeequation (12) can be expressed as

ξ 1514 middot eminus 0096middotac( ) + 5002 (13)

Moreover Figure 18 shows the curve fitting for therelationship between pui and cement content -e followingexpression can describe the fitting curve in Figure 18

pui 00571 middot ac + 040226 (14)

-erefore substituting equations (13) and (14) intoequation (11) it can be expressed as

pu 00085 middot eminus 1514middote minus0096middotac( )+5002( 1113857middotas( 1113857

+ 00571 middot ac + 040226

(15)

p0 and pu in equation (4) are replaced by equations (9) and(15) then equation (4) can be expressed as

p 00085 middot e minus 1514middote minus0096middotac( )+5002( 1113857middotas( + 004624 middot ac + 004624

minus00017 middot e9356middotas

⎛⎝ ⎞⎠

middot 1 minus e(minus 0145middott)

1113872 1113873 + 000165 middot e9356middotas + 001086 middot ac + 008014

(16)

From the published literature [16] ultimate unconfinedcompressive strength increased firstly with adding wheatstraws however with further increasing of wheat strawscontent the ultimate unconfined compressive strength de-creased In test we cannot find the maximum wheat strawscontent and therefore when using equation (16) to predictthe ultimate unconfined compressive strength wheat straws

Table 7 η b and p0i in equation (5) obtained by fitting method

Cement content () Η b p0i Correlation coefficient (R)

0 000176 892416 008035 0999653 000159 910512 011308 0998956 000188 938257 014420 0998449 000167 1008636 017843 099709

Table 8 b and p0i in equation (6) obtained by fitting method

Cement content b p0i Correlation coefficient (R)

0 934882 008053 0999623 924118 011252 0998586 939121 014456 0998329 944322 017848 099709

00 20 40 60 80 100

008

010

012

014

016

018

020

P 0i (

MPa

)

Cement content ()

Figure 15 Curve fitting for the relationship between p0i andcement content

Table 9 pu in equation (3) obtained with equation (4)

Cement content () Wheat straw content() α pu

0

000

0145

042179010 043434015 043685020 044085025 045725

3

000

0145

056437010 057692015 058943020 059343025 061983

6

000

0145

075695010 075950015 076201020 076601025 078241

9

000

0145

092953010 094208015 095459020 095859025 096499

Advances in Materials Science and Engineering 11

content cannot exceed 025 by weight of saline-alkalinesoils In addition when cement content in specimens isgreater than 9 by weight of saline-alkaline soils we cannotperform a series of tests to obtain the influence of cementcontent on ultimate unconfined compressive strength andtherefore in the application of equation (16) cement content

should be less than 9 Moreover for equation (16) derivedfrom the test on specimens with optimum water contentwhen using it to predict the ultimate unconfined com-pressive strength for specimens the range of optimum watercontent for specimens should fall into 127sim145 byweight of saline-alkaline soils

0 cement content

041504200425043004350440044504500455

04650460

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(a)

3 cement content

030010 015 020 025005000Wheat straw content ()

056005650570057505800585059005950600060506100615062006250630

P u (M

Pa)

(b)

0750

0755

0760

0765

0770

0775

0780

0785

0790

6 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(c)

09200925093009350940094509500955096009650970

9 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(d)

Figure 16 Curve fitting for the relationship between pu and wheat straw content for different cement content (a) 0 cement content (b)3 cement content (c) 6 cement content (d) 9 cement content

Table 10 a ς and pui in equation (10) obtained by fitting method

Cement content a ς pui Correlation coefficient (R)

0 000861 639527 041324 0998703 000832 689803 055693 0998376 000857 745161 075670 0998659 000848 832193 091686 099934

Table 11 ς and pui in equation (11) obtained by fitting method

Cement content () a ς pui Correlation coefficient (R)

0

00085

651373 041364 0998693 702611 055628 0998356 768670 074533 0959769 858824 092165 099841

12 Advances in Materials Science and Engineering

34 Validity of Derived Equation (16) for Unconfined Com-pressive Strength of Specimens In order to obtain the reli-ability of derived equation (16) for unconfined compressivestrength of specimens the results from derived equation (16)should be compared with those from tests Based onequation (16) unconfined compressive strength of speci-mens mixed with 6 cement content and 02 wheat strawcontent for different curing periods can be obtained asshown in Table 12 In addition test results for unconfinedcompressive strength of specimens mixed with 6 cementcontent and 02 wheat straw content for different curingperiods are also shown in Table 12

As can be seen from Table 12 most of the deviation forunconfined compression strength falls in the range of260sim300 and the maximum deviation for unconfinedcompression strength can reach 316 when curing period is3 days -erefore compared with the test results the ac-curacy of results from the derived equation (16) is not veryhigh also indicating that equation (16) is only applicable tothe approximate evaluation of unconfined compression

strength of saline-alkaline soils In this paper we onlycompare the test result for specimens with combination ofwheat straw content and cement content already used in thecurrent study When using equation (16) to predict theunconfined compression strength of specimens with anothercombination of wheat straw content and cement contentother than what had been already used in the current studyspecimens should be in the state of maximum densitytherefore compaction tests should be firstly carried out toobtain the optimal moisture content of the specimens

4 Conclusions

In this study a series of tests are conducted to study theeffects of wheat straw and cement on the unconfinedcompression strength of specimens -e effect of wheatstraw and cement inclusions and curing periods on un-confined compression strength is determined -e followingconclusions are derived from these tests

-e inclusion of wheat straw within saline-alkaline soilsand saline-alkaline soils mixed with cement causes an in-crease in unconfined compression strength Increasingwheat straw content can increase the peak axial stress andweaken the brittle behavior of saline-alkaline soils mixedwith cement Moreover unconfined compression strengthof specimens increases with increasing curing periods It isknown that the interface roughness for wheat straw plays animportant role in reinforcing the soil Although it is animportant subject no attempt has yet been made to de-termine the optimum degree of the interface roughness Inaddition based on the data obtained from unconfinedcompression strength test a formula for predicting theunconfined compression strength of specimens related tocement content wheat straw content curing periods and soforth is put forward Compared with test results equation(16) is only applicable to the approximate evaluation ofunconfined compression strength of specimens

In addition in the present study we cannot obtain theinfluence of wheat straw content greater than 025 andorcement content greater than 9 on unconfined compressionstrength of specimens of specimens -erefore the appli-cation scope of equation (16) is limited If more test results ofunconfined compression strength of specimens mixed withwheat straw content greater than 025 andor cementcontent greater than 9 are obtained the application ofequation (16) will be more extensive in predicting the un-confined compression strength of specimens with optimalmoisture content Moreover only unconfined compression

00 20 40 60 80 10050

55

60

65

70

75

80

85

90

Cement content ()

ξ

Figure 17 Curve fitting for the relationship between ξ and cementcontent

00 20 40 60 80 100Cement content ()

10

09

08

07

06

05

04

03

02

01

00

p ui (

MPa

)

Figure 18 Curve fitting for the relationship between pui and ce-ment content

Table 12 Unconfined compression strength obtained from testand calculated value by equation (16)

Curingdays

Calculated value(MPa)

Test result(MPa)

Deviation()

3 0179 0136 3167 0398 0312 27614 0581 0449 29428 0582 0461 26256 0681 0529 286

Advances in Materials Science and Engineering 13

strength tests have been conducted on specimensmixed withwheat straw and cement -erefore investigations should becarried out further through other strength tests like directshear tests triaxial shear tests and so forth to study theinfluence of wheat straw on strength of specimens

Data Availability

-e data used to support the findings of this study are in-cluded within the article

Conflicts of Interest

-e authors declare no conflicts of interest with respect tothe research authorship andor publication of this article

Acknowledgments

-is work was financially supported by National NaturalScience Foundation of China (Grant no 51908430) Doc-toral Scientific Fund Project of Weifang University (Grantno 2017BS14) and Science and Technology Project of High-Tech Zone in Weifang (Grant no 2019KJHM09)

References

[1] R L Michalowski and J Cermak ldquoTriaxial compression ofsand reinforced with fibersrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 129 no 2 pp 125ndash1362003

[2] T Yetimoglu M Inanir and O Esatinanir ldquoA study onbearing capacity of randomly distributed fiber-reinforcedsand fills overlying soft clayrdquo Geotextiles and Geomembranesvol 23 no 2 pp 174ndash183 2005

[3] T Park and S Tan ldquoEnhanced performance of reinforced soilwalls by the inclusion of short fiberrdquo Geotextiles and Geo-membranes vol 23 no 4 pp 348ndash361 2005

[4] C Tang B Shi W Gao F Chen and Y Cai ldquoStrength andmechanical behavior of short polypropylene fiber reinforcedand cement stabilized clayey soilrdquo Geotextiles and Geo-membranes vol 25 no 3 pp 194ndash202 2007

[5] S Salah N Shadi and F Fadi ldquoShear strength of fiber-reinforced sandsrdquo Journal of Geotechnical and Geo-environmental Engineering vol 136 no 3 pp 490ndash499 2010

[6] G A Santiago C Franco N C Consoli and V R BotaroldquoStudy of mechanical behavior of a sand soil reinforced withcuraua treated fibers with asphaltrdquo Materials Science Forumvol 730-732 pp 319ndash324 2012

[7] J Prabakar and R S Sridhar ldquoEffect of random inclusion ofsisal fibre on strength behaviour of soilrdquo Construction andBuilding Materials vol 16 no 2 pp 123ndash131 2002

[8] C Mahipal Singh M Satyendra and M BijayanandaldquoPerformance evaluation of silty sand subgrade reinforcedwith fly ash and fibrerdquoGeotextiles and Geomembranes vol 26no 5 pp 429ndash435 2008

[9] M Bouhicha F Aouissi and S Kenai ldquoPerformance ofcomposite soil reinforced with barley strawrdquo Cement andConcrete Composites vol 27 no 5 pp 617ndash621 2005

[10] N C Consoli M D T Casagrande P D M Prietto andA n -ome ldquoPlate load test on fiber-reinforced soilrdquo Journalof Geotechnical and Geoenvironmental Engineering vol 129no 10 pp 951ndash955 2003

[11] J Yao Experimental Study on Strength Characteristics ofWheat Straw Reinforced soil Changrsquoan University XirsquoanChina 2017

[12] A Adili A Rafig S Giovanni et al ldquoStrength of soil rein-forced with fiber materials (papyrus)rdquo Soil Mechanics andFoundation Engineering vol 48 no 6 pp 241ndash247 2012

[13] Y L Qian ldquoExperimentresearch of mechanical properties ofimproved saline soilrdquo Geotechnical Investigation and Sur-veying vol 5 pp 1ndash4 2003

[14] X S Wang H Q Zhang and M Xue ldquoRoad disease andtreatment in saline soil areardquo Journal of Tongji Universityvol 31 no 10 pp 1178ndash1182 2003

[15] Q LWang Y Chao Y F Liu et al ldquoMechanical properties ofsaline soil under the influence of different factorsrdquo FreseniusEnvironmental Bulletin vol 28 no 2A pp 1366ndash1373 2019

[16] L Wei S X Chai H Z Cai et al ldquoResearch on tensility ofwheat straw for reinforced materialrdquo Rock amp Soil Mechanicsvol 31 no 1 pp 128ndash132 2010

[17] L Wei S X Chai H Z Cai et al ldquoPhysical and mechanicalproperties of wheat straw and unconfined compressivestrength of reinforced inshore saline soil with wheat strawrdquoChina Civil Engineering Journal vol 43 no 3 pp 93ndash982010

[18] M Li S X Chai H P Du et al ldquoReasonable reinforcementposition and shear strength model of reinforced saline soilwith wheat straw and limerdquo Chinese Jourhal of Rock Me-chanics and Engineering vol 29 no sup 2 pp 3923ndash39292010

[19] P Wang S X Chai X Y Wang et al ldquoAnalysis of effectfactors of heavy compaction test for wheat straw-reinforcedsaline soilrdquo Rock and Soil Mechanics vol 32 no 2pp 448ndash452 2011

[20] L Wei S X Chai H Z Cai et al ldquoTriaxial shear strength anddeviatoric stress-strain of saline soils reinforced with wheatstrawsrdquo China Civil Engineering Journal vol 45 no 1pp 109ndash114 2012

[21] H Lu C G Yan X H Yang et al ldquoExperiment on anti-eroding property of reinforced loess with wheat strawrdquoJournal of Changrsquoan University (Natural Science Edition)vol 37 no 1 pp 24ndash32 2017

[22] J B Hao X MWei J Yao et al ldquoStrength characteristics andmesostructure of wheat straw einforced soilrdquo Journal of TongjiUniversity (Natural Science) vol 47 no 6 pp 764ndash831 2019

[23] GB50007-2011 Code for Design of Building foundationMinistry of Housing and Urban-Rural Development BeijingChina 2012

[24] JTG D30-2015 Specifications for Design of Highway Sub-grades China Communications Publishing amp Media Man-agement Co Ltd Beijing China 2016

[25] GBT 50123-1999 Standard for Soil Test Method Ministry ofConstruction Beijing China 2000

14 Advances in Materials Science and Engineering

should be in the state of maximum density which can beobtained from compaction tests Table 4 also shows theoptimum moisture content for each group

Table 3 Chemical content and physical properties of ordinary Portland cement

SiO2 Al2O3 Fe2O3 CaO MgO SO3 LOI Specific surface Compressive strength (28 days)223 46 36 653 29 38 17 373m2kg 448MPa

Figure 2 Wheat straws used in test

100μm EHT = 500kVWD = 72mm

Signal A = SE2Mag = 150X

Date 27 Nov 2019Time 103601

Figure 3 Cross section of wheat straw

Table 1 Basic mechanical properties for saline-alkaline soils

Specificgravity Gs

Consistency index Compaction test Grain contentLiquid limit

wL ()Plastic limit

wp ()Plasticindex IP

Maximum drydensity ρd (gmiddotcmminus3)

Optimum watercontent s ()

0074sim0038(mm)

0038sim0008(mm)

lt0008(mm)

271 325 169 156 185 168 225 573 211

Table 2 Ion content in saline-alkaline soils g

CO3minus 2 HCO3

minus CIminus SO42minus Ca2+ Mg2+ K+ +Na+ PH value Content of soluble salt

0019 0171 18011 0871 0369 0761 9931 772 332lowast-e ion content is the ion mass in 1000 g saline-alkaline soils

Figure 4 Specimens for unconfined compressive test

Table 4 Cement and wheat straw content and optimum moisturecontent in specimens

Specimenno

Cementcontent ()

Wheat strawcontent ()

Optimum moisturecontent ()

S 0 0 127W 1 0 010 129W 2 0 015 129W 3 0 020 131W 4 0 025 131C 1 3 0 130C 2 6 0 135C 3 9 0 139CW 1 3 010 131CW 2 3 015 131CW 3 3 020 133CW 4 3 025 133CW 5 6 010 138CW 6 6 015 138CW 7 6 020 141CW 8 6 025 141CW 9 9 010 143CW 10 9 015 143CW 11 9 020 145CW 12 9 025 145

Advances in Materials Science and Engineering 3

23 Unconfined Compression Tests In order to obtain un-confined compression strength of specimens conventionalunconfined compression apparatus is used in test as shownin Figure 5 In the unconfined compression test axial forceand corresponding displacement can be obtained auto-matically with multichannel real-time record system Inaddition unconfined compression tests are carried out at thelast day of curing period for specimens For the conventionalunconfined compression apparatus used in test the loadingrate is set to be 24mmmin until specimens failed

3 Results and Discussions

31 Effect of Wheat Straws on Unconfined CompressiveStrength of Specimens In this paper based on the resultsfrom unconfined compressive tests on specimens mixedwith cement and wheat straws after curing for 14 days thestress-strain curves are obtained as shown in Figures 6(a)ndash6(c) As can be seen from Figure 6(a) with increasing wheatstraw content unconfined compressive strength of speci-mens also increases However further increase of wheatstraw content does not significantly improve the peak axialstress Furthermore specimens mixed with increasing wheatstraw content exhibit more ductile behavior than that notmixed with wheat straws Figure 6(b) shows the influence ofcement content on unconfined compressive strength ofspecimens As can be seen from Figure 6(b) increasingcement content can improve the peak axial stress of spec-imens andmeanwhile exhibit more brittle behavior than thatnot mixed with cement Figure 6(c) shows the influence ofwheat straw content on unconfined compressive strength ofspecimens mixed with cement As can be seen fromFigure 6(c) when the cement content is constant in spec-imens the influence of increasing wheat straw content onunconfined compressive strength of specimens is similar tothat in Figure 6(a)

-e influence of wheat straw content on unconfinedcompressive strength of specimens mixed with differentcement content after curing for 14 days is shown in Figure 7As can be seen from Figure 7 not only for cementedspecimens but also for uncemented specimens the addedwheat straws can increase unconfined compressive strengthof specimens As shown in Figure 7 after 01 wheat strawswere added unconfined compressive strength of specimensreinforced with 3 6 and 9 cement content increasesfrom 018 to 022MPa from 036 to 040MPa and from 051to 053MPa respectively showing that added 01 wheatstraws content has little effect on the improvement of un-confined compressive strength of specimens However after025 wheat straws content is added unconfined com-pressive strength of specimens reinforced with 3 6 and9 cement content increases from 019 to 038MPa from036 to 052MPa and from 049 to 058MPa respectively

-e influence of curing periods on unconfined com-pressive strength of specimens mixed with 3 cementcontent and 01 wheat straw content is shown in Figure 8As can be seen from Figure 8 unconfined compressivestrength of specimens increases with curing periods Inaddition when curing periods are less than 14 days the

failure of specimens exhibits the ductile behavior Howeverwhen curing periods are greater than 14 days the brittlebehavior of failure of specimens becomes more and moreobvious

32 Effect of Wheat Straw Content on Failure Mechanism ofSpecimens In this section the specimens after curing for 28days are used in unconfined compressive strength testFigures 9(a)ndash9(e) show the failure of specimens only mixedwith wheat straws As can be seen from Figure 9(a) whenwheat straws are not added to specimen the failure occursmainly on the bottom of specimens showing the shearfailure mode When the wheat straw content is 010 byweight the failure also occurs mainly on the bottom ofspecimens however the shear plane does not form asshown in Figure 9(b) When the wheat straw content isincreased to 015 by weight a large shear plane formswhich extends to the top of specimens as shown inFigure 9(c) As can be seen from Figure 9(d) when the wheatstraw content is increased to 020 by weight there are twofailure modes in specimens one shear failure and anotherbottom failure of specimens When the wheat straw contentis increased to 025 by weight the bottom failure inspecimens only occurs and shear plane does not form asshown in Figure 9(e)

Figures 10(a)ndash10(e) show the failure of specimens mixedwith different wheat straws content and 6 cement contentWhen wheat straws are not added in the specimens the shearplane failure is mainly exhibited which also shows the brittlebehavior of specimens as shown in Figure 10(a) Howeverwhen wheat straws are added in the specimens and the wheatstraw content reaches 010 and 015 by weight a largeshear plane forms in specimens as shown in Figures 10(b)and 10(c) As can be seen from Figure 10(d) when the wheatstraw content is 020 by weight only the bottom failure ofspecimens is shown and shear plane does not form Howeverthe top failure of specimens occurs when the wheat strawcontent reaches 025 by weight and also shear plane does notform in specimens as shown in Figure 10(e)

Based on the results of unconfined compressive strengthtests on specimens mixed with 3 cement content and 01wheat straw content the effect of curing periods on thefailure of specimens can be obtained as shown inFigures 11(a)ndash11(e) As can be seen from Figures 11(a) and11(b) when the curing period is less than 7 days the failure

Figure 5 Unconfined compression apparatus

4 Advances in Materials Science and Engineering

of the bottom of specimens occurs and it does not obviouslyexhibit the shear plane When the curing period is 14 daysthere are two simultaneous failure modes in specimens asshown in Figure 11(c) However as can be seen fromFigures 11(d) and 11(e) when the curing period is greaterthan 14 days only shear plane failure occurs in specimensDuring the unconfined compressive strength tests we alsofind that the increasing of curing periods can improve thebrittle behavior of specimens and the trend for influence ofcuring periods on the brittle behavior of specimens is similarto that shown in Figure 8

33 Prediction for Unconfined Compressive Strength ofSpecimens Mixed with Wheat Straws and Cement As

discussed above the factors affecting unconfined com-pressive strength of specimens include wheat straw contentcement content and curing periods In this section a for-mula that can predict unconfined compressive strength ofspecimens is put forward based on the results from un-confined compressive strength test on saline-alkaline soilsmixed with wheat straws and cement Figures 12(a)ndash12(d)show the increasing of unconfined compressive strength ofspecimens with curing periods

As can be seen from Figures 12(a)ndash12(d) when thespecimens have the same cement content unconfinedcompressive strength of specimen increases with increasingwheat straw content Based on the data from Figures 12(a)ndash12(d) the curve fitting for the relationship between curingperiod and unconfined compressive strength of specimens

00 10 20 30 40 50 60 70 80 90000

002

004

006

008

010

012

014

016

Axial strain ε ()

Axi

al st

ress

σ (M

Pa)

0 wheat straw010 wheat straw 015 wheat straw

020 wheat straw025 wheat straw

(a)

00 10 20 30 40 50 60 70Axial strain ε ()

00

01

02

03

04

05

06

Axi

al st

ress

σ (M

Pa)

00 cement30 cement

60 cement90 cement

(b)

00 10 20 30 40 50 60Axial strain ε ()

00

01

02

03

04

05

06

Axi

al st

ress

σ (M

Pa)

0 wheat straw + 6 cement010 wheat straw + 6 cement 015 wheat straw + 6 cement 020 wheat straw + 6 cement025 wheat straw + 6 cement

(c)

Figure 6 Stress-strain curves of specimens after 14-day curing period (a) Specimens mixed with different wheat straw content (b)Specimens mixed with different cement content (c) Specimens mixed with 6 cement content and different wheat straw content

Advances in Materials Science and Engineering 5

005 010 025020 030000 015Wheat straw content ()

01

02

03

04

05

06

07

08

Axi

al st

ress

σ (M

Pa)

0 cement3 cement

6 cement9 cement

Figure 7 Relationship between wheat straw content and unconfined compressive strength after curing for 14 days

0000 0005 0010 0015 0020 0025 0030 0035 004000

01

02

03

04

05

06

Axi

al st

ress

σ (M

Pa)

Axial strain ε ()

3 days7 days14 days

28 days56 days

Figure 8 Influence of curing periods on unconfined compressive strength of specimens

(a) (b) (c) (d) (e)

Figure 9 Effect of wheat straw content on failure mechanism of specimens (a) 0 wheat straw content (b) 010 wheat straw content (c)015 wheat straw content (d) 020 wheat straw content (e) 025 wheat straw content

6 Advances in Materials Science and Engineering

mixed with 02 wheat straw content and different cementcontent is shown in Figures 13(a)ndash13(d)

In Figures 13(a)ndash13(d) the curve fitting can be expressedby the following expression

p pu minus p0( 1113857 middot 1 minus e(minus αmiddott)

1113872 1113873 + p0 (3)

where p is unconfined compressive strength of specimens tis curing period pu is ultimate unconfined compressivestrength p0 is initial unconfined compressive strength α isthe coefficient related to the shape of curves

In equation (3) using fitting method pu p0 and α canbe obtained based on the data from Figures 12(a)ndash12(d) asshown in Table 5

As shown in Table 5 α is in the range of 014398 to014643 showing that the change of the value of α is verylittle -e mean value for α is 014533 -erefore in order tosimplify equation (1) the value of α is replaced by 0145 andequation (1) can be expressed as

p pu minus p0( 1113857 middot 1 minus e(minus 0145middott)

1113872 1113873 + p0 (4)

331 Initial Unconfined Compressive Strength p0 Inequation (4) p0 and pu can also be obtained based on the datafrom Figures 10(a)ndash10(d) by fitting method as shown inTable 6 Based on the data fromTable 6 the curve fitting for therelationship between p0 and wheat straw content for differentcement content can be obtained as shown in Figure 14

For the curve fitting in Figures 14(a)ndash14(d) it can bedescribed by the following expression

p0 η middot ebmiddotas + p0i (5)

where η is the coefficient for curve growth as is wheatstraw content b is the exponent p0i is initial uncon-fined compressive strength only related to cement con-tent Based on the data from Table 6 η b and p0i inequation (5) can be obtained by fitting method as shownin Table 7

As can be seen from Table 7 the change of η is very littleand the mean value for η is 00017 -erefore equation (5)can be simplified and expressed as

p0 00017 middot ebmiddotas + p0i (6)

Similarly based on the data from Table 6 and equation(6) b and p0i can be obtained by fitting method as shown inTable 8

As shown in Table 8 the change of b is also very little andthe mean value for b is 9356 -erefore in order to simplifyequation (6) b is replaced by 9356 in equation (6) and thenit is expressed as

p0 00017 middot e9356middotas + p0i (7)

Moreover as can be seen from Table 8 p0i is related tocement content Based on the data from Table 8 the rela-tionship between p0i and cement content can also be ob-tained as shown in Figure 15

(a) (b) (c) (d) (e)

Figure 10 Effect of wheat straw content on failure mechanism of specimens mixed with 6 cement content (a) 0 wheat straw content (b)010 wheat straw content (c) 015 wheat straw content (d) 020 wheat straw content (e) 025 wheat straw content

(a) (b) (c) (d) (e)

Figure 11 Effect of curing period on failure mechanism of specimens mixed with 3 cement content and 01 wheat straw content (a) 3days (b) 7 days (c) 14 days (d) 28 days (e) 56 days

Advances in Materials Science and Engineering 7

-e curve fitting for relationship between p0i and cementcontent in Figure 15 can be expressed as

p0i 008014 + 001086 middot ac (8)

where ac is cement content -erefore equation (7) canbe expressed as

p0 00017 middot e9356middotas + 001086 middot ac + 008014 (9)

332 Ultimate Unconfined Compressive Strength pu In thissection equation (4) is also used to determine the value of puHowever in equation (4)p0 can be obtained from equation (9)

according to the cement content and wheat straw contentFurthermore based on the data from Figures 12(a)ndash12(d) pucan be obtained with equation (3) as shown in Table 9

For the curve fitting in Figure 16 it can be described bythe following expression

pu a middot eminus ςmiddotas( ) + pui (10)

where a is the coefficient related to curve growth as is wheatstraw content b is the exponent pui is initial ultimateunconfined compressive strength of specimens only relatedto cement content Similarly a ς and pui in equation (10)can be obtained by fitting method based on the data fromTable 9 as shown in Table 10

0 10 20 30 40 50 60 7000

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing age (day)

0 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(a)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing age (day)

3 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(b)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing age (day)

6 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(c)

00

01

02

03

04

05

06

07Pe

ak st

ress

σ (M

Pa)

0 10 20 30 40 50 60 70Curing age (day)

9 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(d)

Figure 12 Effect of curing periods on unconfined compressive strength of specimens mixed with wheat straws and different cementcontent (a) 0 cement content (b) 3 cement content (c) 6 cement content (d) 9 cement content

8 Advances in Materials Science and Engineering

0 10 20 30 40 50 60 7000

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing aging (day)

0 cement content

(a)

000 10 20 30 40 50 60 70

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing aging (day)

3 cement content

(b)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing aging (day)

6 cement content

(c)

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing aging (day)

9 cement content

(d)

Figure 13 Curve fitting for the relationship between curing periods and unconfined compressive strength of specimens mixed with 02wheat straw and different cement content (a) 0 cement content (b) 3 cement content (c) 6 cement content (d) 9 cement content

Table 5 pu p0 and α in equation (3) obtained by fitting method

Cement content () Wheat straw content () A pu p0 Correlation coefficient (R)

0

000 014588 043154 009152 098592010 014516 044304 009313 098594015 014618 044932 009624 098513020 014544 045447 010006 098573025 014475 046229 010691 098532

3

000 014579 058251 012124 098826010 014551 058510 012383 098837015 014540 058738 012611 098756020 014464 059306 013179 098620025 014476 059871 013744 098922

6

000 014398 073439 015303 098871010 014613 073703 015567 098887015 014558 074029 015893 098998020 014623 074398 016262 098928025 014489 074994 016858 099096

9

000 014483 089900 018327 099765010 014643 090140 018567 099796015 014568 090410 018837 099796020 014456 090841 019268 099864025 014483 091405 019832 099801

Advances in Materials Science and Engineering 9

Table 6 p0 and pu in equation (4) obtained by fitting method

Cement content () Wheat straw content () α pu p0 Correlation coefficient (R)

0

000

0145

042040 008205 098389010 043203 008498 098396015 043892 008708 098338020 044639 009132 098464025 045536 009759 098451

3

000

0145

056306 011459 098765010 057668 011623 098763015 058741 011906 098752020 059589 012309 098607025 061033 012917 098894

6

000

0145

075501 014632 098870010 075883 014825 098885015 076059 015161 098966020 076642 015566 098839025 078146 016166 099062

9

000

0145

093233 018034 099679010 094507 018203 099703015 095207 018589 099711020 095780 018931 099748025 096357 019594 099705

000

002

004

006

008

010

012

014

016

018

020

022

024

026

0080

0085

0090

0095

0100

P 0 (M

Pa)

Wheat straw content as ()

0 cement content

(a)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0110

0115

0120

0125

0130

3 cement content

(b)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0140

0145

0150

0155

0160

0165

0170

6 cement content

(c)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0175

0180

0185

0190

0195

0200

9 cement content

(d)

Figure 14 Curve fitting for the relationship between p0 and wheat straw content for different cement content (a) 0 cement content (b)3 cement content (c) 6 cement content (d) 9 cement content

10 Advances in Materials Science and Engineering

As can be seen from Table 10 a is in the range of 000832to 000861 showing that the change of a is very little -emean value for a is 000849 and the value of a in equation(10) is replaced by 00085 then equation (10) can beexpressed as

pu 00085 middot eminus ξmiddotas( ) + pui (11)

-en based on equation (11) and the data in Table 9 ςand pui can be further obtained by fitting method as shownin Table 11

Figure 17 shows the curve fitting for the relationshipbetween ξ and cement content and the following expressioncan describe the curve fitting

ξ a1 middot eminus b1 middotac( ) + ξ0 (12)

where a1 is the coefficient related to curve growth ac iscement content b1 is the exponent ξ0 is initial value of ξonly related to cement content Based on the data fromTable 11 a1 b1 and ξ0 can be obtained by fitting methodwhich are 1514 0096 and 5002 respectively -ereforeequation (12) can be expressed as

ξ 1514 middot eminus 0096middotac( ) + 5002 (13)

Moreover Figure 18 shows the curve fitting for therelationship between pui and cement content -e followingexpression can describe the fitting curve in Figure 18

pui 00571 middot ac + 040226 (14)

-erefore substituting equations (13) and (14) intoequation (11) it can be expressed as

pu 00085 middot eminus 1514middote minus0096middotac( )+5002( 1113857middotas( 1113857

+ 00571 middot ac + 040226

(15)

p0 and pu in equation (4) are replaced by equations (9) and(15) then equation (4) can be expressed as

p 00085 middot e minus 1514middote minus0096middotac( )+5002( 1113857middotas( + 004624 middot ac + 004624

minus00017 middot e9356middotas

⎛⎝ ⎞⎠

middot 1 minus e(minus 0145middott)

1113872 1113873 + 000165 middot e9356middotas + 001086 middot ac + 008014

(16)

From the published literature [16] ultimate unconfinedcompressive strength increased firstly with adding wheatstraws however with further increasing of wheat strawscontent the ultimate unconfined compressive strength de-creased In test we cannot find the maximum wheat strawscontent and therefore when using equation (16) to predictthe ultimate unconfined compressive strength wheat straws

Table 7 η b and p0i in equation (5) obtained by fitting method

Cement content () Η b p0i Correlation coefficient (R)

0 000176 892416 008035 0999653 000159 910512 011308 0998956 000188 938257 014420 0998449 000167 1008636 017843 099709

Table 8 b and p0i in equation (6) obtained by fitting method

Cement content b p0i Correlation coefficient (R)

0 934882 008053 0999623 924118 011252 0998586 939121 014456 0998329 944322 017848 099709

00 20 40 60 80 100

008

010

012

014

016

018

020

P 0i (

MPa

)

Cement content ()

Figure 15 Curve fitting for the relationship between p0i andcement content

Table 9 pu in equation (3) obtained with equation (4)

Cement content () Wheat straw content() α pu

0

000

0145

042179010 043434015 043685020 044085025 045725

3

000

0145

056437010 057692015 058943020 059343025 061983

6

000

0145

075695010 075950015 076201020 076601025 078241

9

000

0145

092953010 094208015 095459020 095859025 096499

Advances in Materials Science and Engineering 11

content cannot exceed 025 by weight of saline-alkalinesoils In addition when cement content in specimens isgreater than 9 by weight of saline-alkaline soils we cannotperform a series of tests to obtain the influence of cementcontent on ultimate unconfined compressive strength andtherefore in the application of equation (16) cement content

should be less than 9 Moreover for equation (16) derivedfrom the test on specimens with optimum water contentwhen using it to predict the ultimate unconfined com-pressive strength for specimens the range of optimum watercontent for specimens should fall into 127sim145 byweight of saline-alkaline soils

0 cement content

041504200425043004350440044504500455

04650460

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(a)

3 cement content

030010 015 020 025005000Wheat straw content ()

056005650570057505800585059005950600060506100615062006250630

P u (M

Pa)

(b)

0750

0755

0760

0765

0770

0775

0780

0785

0790

6 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(c)

09200925093009350940094509500955096009650970

9 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(d)

Figure 16 Curve fitting for the relationship between pu and wheat straw content for different cement content (a) 0 cement content (b)3 cement content (c) 6 cement content (d) 9 cement content

Table 10 a ς and pui in equation (10) obtained by fitting method

Cement content a ς pui Correlation coefficient (R)

0 000861 639527 041324 0998703 000832 689803 055693 0998376 000857 745161 075670 0998659 000848 832193 091686 099934

Table 11 ς and pui in equation (11) obtained by fitting method

Cement content () a ς pui Correlation coefficient (R)

0

00085

651373 041364 0998693 702611 055628 0998356 768670 074533 0959769 858824 092165 099841

12 Advances in Materials Science and Engineering

34 Validity of Derived Equation (16) for Unconfined Com-pressive Strength of Specimens In order to obtain the reli-ability of derived equation (16) for unconfined compressivestrength of specimens the results from derived equation (16)should be compared with those from tests Based onequation (16) unconfined compressive strength of speci-mens mixed with 6 cement content and 02 wheat strawcontent for different curing periods can be obtained asshown in Table 12 In addition test results for unconfinedcompressive strength of specimens mixed with 6 cementcontent and 02 wheat straw content for different curingperiods are also shown in Table 12

As can be seen from Table 12 most of the deviation forunconfined compression strength falls in the range of260sim300 and the maximum deviation for unconfinedcompression strength can reach 316 when curing period is3 days -erefore compared with the test results the ac-curacy of results from the derived equation (16) is not veryhigh also indicating that equation (16) is only applicable tothe approximate evaluation of unconfined compression

strength of saline-alkaline soils In this paper we onlycompare the test result for specimens with combination ofwheat straw content and cement content already used in thecurrent study When using equation (16) to predict theunconfined compression strength of specimens with anothercombination of wheat straw content and cement contentother than what had been already used in the current studyspecimens should be in the state of maximum densitytherefore compaction tests should be firstly carried out toobtain the optimal moisture content of the specimens

4 Conclusions

In this study a series of tests are conducted to study theeffects of wheat straw and cement on the unconfinedcompression strength of specimens -e effect of wheatstraw and cement inclusions and curing periods on un-confined compression strength is determined -e followingconclusions are derived from these tests

-e inclusion of wheat straw within saline-alkaline soilsand saline-alkaline soils mixed with cement causes an in-crease in unconfined compression strength Increasingwheat straw content can increase the peak axial stress andweaken the brittle behavior of saline-alkaline soils mixedwith cement Moreover unconfined compression strengthof specimens increases with increasing curing periods It isknown that the interface roughness for wheat straw plays animportant role in reinforcing the soil Although it is animportant subject no attempt has yet been made to de-termine the optimum degree of the interface roughness Inaddition based on the data obtained from unconfinedcompression strength test a formula for predicting theunconfined compression strength of specimens related tocement content wheat straw content curing periods and soforth is put forward Compared with test results equation(16) is only applicable to the approximate evaluation ofunconfined compression strength of specimens

In addition in the present study we cannot obtain theinfluence of wheat straw content greater than 025 andorcement content greater than 9 on unconfined compressionstrength of specimens of specimens -erefore the appli-cation scope of equation (16) is limited If more test results ofunconfined compression strength of specimens mixed withwheat straw content greater than 025 andor cementcontent greater than 9 are obtained the application ofequation (16) will be more extensive in predicting the un-confined compression strength of specimens with optimalmoisture content Moreover only unconfined compression

00 20 40 60 80 10050

55

60

65

70

75

80

85

90

Cement content ()

ξ

Figure 17 Curve fitting for the relationship between ξ and cementcontent

00 20 40 60 80 100Cement content ()

10

09

08

07

06

05

04

03

02

01

00

p ui (

MPa

)

Figure 18 Curve fitting for the relationship between pui and ce-ment content

Table 12 Unconfined compression strength obtained from testand calculated value by equation (16)

Curingdays

Calculated value(MPa)

Test result(MPa)

Deviation()

3 0179 0136 3167 0398 0312 27614 0581 0449 29428 0582 0461 26256 0681 0529 286

Advances in Materials Science and Engineering 13

strength tests have been conducted on specimensmixed withwheat straw and cement -erefore investigations should becarried out further through other strength tests like directshear tests triaxial shear tests and so forth to study theinfluence of wheat straw on strength of specimens

Data Availability

-e data used to support the findings of this study are in-cluded within the article

Conflicts of Interest

-e authors declare no conflicts of interest with respect tothe research authorship andor publication of this article

Acknowledgments

-is work was financially supported by National NaturalScience Foundation of China (Grant no 51908430) Doc-toral Scientific Fund Project of Weifang University (Grantno 2017BS14) and Science and Technology Project of High-Tech Zone in Weifang (Grant no 2019KJHM09)

References

[1] R L Michalowski and J Cermak ldquoTriaxial compression ofsand reinforced with fibersrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 129 no 2 pp 125ndash1362003

[2] T Yetimoglu M Inanir and O Esatinanir ldquoA study onbearing capacity of randomly distributed fiber-reinforcedsand fills overlying soft clayrdquo Geotextiles and Geomembranesvol 23 no 2 pp 174ndash183 2005

[3] T Park and S Tan ldquoEnhanced performance of reinforced soilwalls by the inclusion of short fiberrdquo Geotextiles and Geo-membranes vol 23 no 4 pp 348ndash361 2005

[4] C Tang B Shi W Gao F Chen and Y Cai ldquoStrength andmechanical behavior of short polypropylene fiber reinforcedand cement stabilized clayey soilrdquo Geotextiles and Geo-membranes vol 25 no 3 pp 194ndash202 2007

[5] S Salah N Shadi and F Fadi ldquoShear strength of fiber-reinforced sandsrdquo Journal of Geotechnical and Geo-environmental Engineering vol 136 no 3 pp 490ndash499 2010

[6] G A Santiago C Franco N C Consoli and V R BotaroldquoStudy of mechanical behavior of a sand soil reinforced withcuraua treated fibers with asphaltrdquo Materials Science Forumvol 730-732 pp 319ndash324 2012

[7] J Prabakar and R S Sridhar ldquoEffect of random inclusion ofsisal fibre on strength behaviour of soilrdquo Construction andBuilding Materials vol 16 no 2 pp 123ndash131 2002

[8] C Mahipal Singh M Satyendra and M BijayanandaldquoPerformance evaluation of silty sand subgrade reinforcedwith fly ash and fibrerdquoGeotextiles and Geomembranes vol 26no 5 pp 429ndash435 2008

[9] M Bouhicha F Aouissi and S Kenai ldquoPerformance ofcomposite soil reinforced with barley strawrdquo Cement andConcrete Composites vol 27 no 5 pp 617ndash621 2005

[10] N C Consoli M D T Casagrande P D M Prietto andA n -ome ldquoPlate load test on fiber-reinforced soilrdquo Journalof Geotechnical and Geoenvironmental Engineering vol 129no 10 pp 951ndash955 2003

[11] J Yao Experimental Study on Strength Characteristics ofWheat Straw Reinforced soil Changrsquoan University XirsquoanChina 2017

[12] A Adili A Rafig S Giovanni et al ldquoStrength of soil rein-forced with fiber materials (papyrus)rdquo Soil Mechanics andFoundation Engineering vol 48 no 6 pp 241ndash247 2012

[13] Y L Qian ldquoExperimentresearch of mechanical properties ofimproved saline soilrdquo Geotechnical Investigation and Sur-veying vol 5 pp 1ndash4 2003

[14] X S Wang H Q Zhang and M Xue ldquoRoad disease andtreatment in saline soil areardquo Journal of Tongji Universityvol 31 no 10 pp 1178ndash1182 2003

[15] Q LWang Y Chao Y F Liu et al ldquoMechanical properties ofsaline soil under the influence of different factorsrdquo FreseniusEnvironmental Bulletin vol 28 no 2A pp 1366ndash1373 2019

[16] L Wei S X Chai H Z Cai et al ldquoResearch on tensility ofwheat straw for reinforced materialrdquo Rock amp Soil Mechanicsvol 31 no 1 pp 128ndash132 2010

[17] L Wei S X Chai H Z Cai et al ldquoPhysical and mechanicalproperties of wheat straw and unconfined compressivestrength of reinforced inshore saline soil with wheat strawrdquoChina Civil Engineering Journal vol 43 no 3 pp 93ndash982010

[18] M Li S X Chai H P Du et al ldquoReasonable reinforcementposition and shear strength model of reinforced saline soilwith wheat straw and limerdquo Chinese Jourhal of Rock Me-chanics and Engineering vol 29 no sup 2 pp 3923ndash39292010

[19] P Wang S X Chai X Y Wang et al ldquoAnalysis of effectfactors of heavy compaction test for wheat straw-reinforcedsaline soilrdquo Rock and Soil Mechanics vol 32 no 2pp 448ndash452 2011

[20] L Wei S X Chai H Z Cai et al ldquoTriaxial shear strength anddeviatoric stress-strain of saline soils reinforced with wheatstrawsrdquo China Civil Engineering Journal vol 45 no 1pp 109ndash114 2012

[21] H Lu C G Yan X H Yang et al ldquoExperiment on anti-eroding property of reinforced loess with wheat strawrdquoJournal of Changrsquoan University (Natural Science Edition)vol 37 no 1 pp 24ndash32 2017

[22] J B Hao X MWei J Yao et al ldquoStrength characteristics andmesostructure of wheat straw einforced soilrdquo Journal of TongjiUniversity (Natural Science) vol 47 no 6 pp 764ndash831 2019

[23] GB50007-2011 Code for Design of Building foundationMinistry of Housing and Urban-Rural Development BeijingChina 2012

[24] JTG D30-2015 Specifications for Design of Highway Sub-grades China Communications Publishing amp Media Man-agement Co Ltd Beijing China 2016

[25] GBT 50123-1999 Standard for Soil Test Method Ministry ofConstruction Beijing China 2000

14 Advances in Materials Science and Engineering

23 Unconfined Compression Tests In order to obtain un-confined compression strength of specimens conventionalunconfined compression apparatus is used in test as shownin Figure 5 In the unconfined compression test axial forceand corresponding displacement can be obtained auto-matically with multichannel real-time record system Inaddition unconfined compression tests are carried out at thelast day of curing period for specimens For the conventionalunconfined compression apparatus used in test the loadingrate is set to be 24mmmin until specimens failed

3 Results and Discussions

31 Effect of Wheat Straws on Unconfined CompressiveStrength of Specimens In this paper based on the resultsfrom unconfined compressive tests on specimens mixedwith cement and wheat straws after curing for 14 days thestress-strain curves are obtained as shown in Figures 6(a)ndash6(c) As can be seen from Figure 6(a) with increasing wheatstraw content unconfined compressive strength of speci-mens also increases However further increase of wheatstraw content does not significantly improve the peak axialstress Furthermore specimens mixed with increasing wheatstraw content exhibit more ductile behavior than that notmixed with wheat straws Figure 6(b) shows the influence ofcement content on unconfined compressive strength ofspecimens As can be seen from Figure 6(b) increasingcement content can improve the peak axial stress of spec-imens andmeanwhile exhibit more brittle behavior than thatnot mixed with cement Figure 6(c) shows the influence ofwheat straw content on unconfined compressive strength ofspecimens mixed with cement As can be seen fromFigure 6(c) when the cement content is constant in spec-imens the influence of increasing wheat straw content onunconfined compressive strength of specimens is similar tothat in Figure 6(a)

-e influence of wheat straw content on unconfinedcompressive strength of specimens mixed with differentcement content after curing for 14 days is shown in Figure 7As can be seen from Figure 7 not only for cementedspecimens but also for uncemented specimens the addedwheat straws can increase unconfined compressive strengthof specimens As shown in Figure 7 after 01 wheat strawswere added unconfined compressive strength of specimensreinforced with 3 6 and 9 cement content increasesfrom 018 to 022MPa from 036 to 040MPa and from 051to 053MPa respectively showing that added 01 wheatstraws content has little effect on the improvement of un-confined compressive strength of specimens However after025 wheat straws content is added unconfined com-pressive strength of specimens reinforced with 3 6 and9 cement content increases from 019 to 038MPa from036 to 052MPa and from 049 to 058MPa respectively

-e influence of curing periods on unconfined com-pressive strength of specimens mixed with 3 cementcontent and 01 wheat straw content is shown in Figure 8As can be seen from Figure 8 unconfined compressivestrength of specimens increases with curing periods Inaddition when curing periods are less than 14 days the

failure of specimens exhibits the ductile behavior Howeverwhen curing periods are greater than 14 days the brittlebehavior of failure of specimens becomes more and moreobvious

32 Effect of Wheat Straw Content on Failure Mechanism ofSpecimens In this section the specimens after curing for 28days are used in unconfined compressive strength testFigures 9(a)ndash9(e) show the failure of specimens only mixedwith wheat straws As can be seen from Figure 9(a) whenwheat straws are not added to specimen the failure occursmainly on the bottom of specimens showing the shearfailure mode When the wheat straw content is 010 byweight the failure also occurs mainly on the bottom ofspecimens however the shear plane does not form asshown in Figure 9(b) When the wheat straw content isincreased to 015 by weight a large shear plane formswhich extends to the top of specimens as shown inFigure 9(c) As can be seen from Figure 9(d) when the wheatstraw content is increased to 020 by weight there are twofailure modes in specimens one shear failure and anotherbottom failure of specimens When the wheat straw contentis increased to 025 by weight the bottom failure inspecimens only occurs and shear plane does not form asshown in Figure 9(e)

Figures 10(a)ndash10(e) show the failure of specimens mixedwith different wheat straws content and 6 cement contentWhen wheat straws are not added in the specimens the shearplane failure is mainly exhibited which also shows the brittlebehavior of specimens as shown in Figure 10(a) Howeverwhen wheat straws are added in the specimens and the wheatstraw content reaches 010 and 015 by weight a largeshear plane forms in specimens as shown in Figures 10(b)and 10(c) As can be seen from Figure 10(d) when the wheatstraw content is 020 by weight only the bottom failure ofspecimens is shown and shear plane does not form Howeverthe top failure of specimens occurs when the wheat strawcontent reaches 025 by weight and also shear plane does notform in specimens as shown in Figure 10(e)

Based on the results of unconfined compressive strengthtests on specimens mixed with 3 cement content and 01wheat straw content the effect of curing periods on thefailure of specimens can be obtained as shown inFigures 11(a)ndash11(e) As can be seen from Figures 11(a) and11(b) when the curing period is less than 7 days the failure

Figure 5 Unconfined compression apparatus

4 Advances in Materials Science and Engineering

of the bottom of specimens occurs and it does not obviouslyexhibit the shear plane When the curing period is 14 daysthere are two simultaneous failure modes in specimens asshown in Figure 11(c) However as can be seen fromFigures 11(d) and 11(e) when the curing period is greaterthan 14 days only shear plane failure occurs in specimensDuring the unconfined compressive strength tests we alsofind that the increasing of curing periods can improve thebrittle behavior of specimens and the trend for influence ofcuring periods on the brittle behavior of specimens is similarto that shown in Figure 8

33 Prediction for Unconfined Compressive Strength ofSpecimens Mixed with Wheat Straws and Cement As

discussed above the factors affecting unconfined com-pressive strength of specimens include wheat straw contentcement content and curing periods In this section a for-mula that can predict unconfined compressive strength ofspecimens is put forward based on the results from un-confined compressive strength test on saline-alkaline soilsmixed with wheat straws and cement Figures 12(a)ndash12(d)show the increasing of unconfined compressive strength ofspecimens with curing periods

As can be seen from Figures 12(a)ndash12(d) when thespecimens have the same cement content unconfinedcompressive strength of specimen increases with increasingwheat straw content Based on the data from Figures 12(a)ndash12(d) the curve fitting for the relationship between curingperiod and unconfined compressive strength of specimens

00 10 20 30 40 50 60 70 80 90000

002

004

006

008

010

012

014

016

Axial strain ε ()

Axi

al st

ress

σ (M

Pa)

0 wheat straw010 wheat straw 015 wheat straw

020 wheat straw025 wheat straw

(a)

00 10 20 30 40 50 60 70Axial strain ε ()

00

01

02

03

04

05

06

Axi

al st

ress

σ (M

Pa)

00 cement30 cement

60 cement90 cement

(b)

00 10 20 30 40 50 60Axial strain ε ()

00

01

02

03

04

05

06

Axi

al st

ress

σ (M

Pa)

0 wheat straw + 6 cement010 wheat straw + 6 cement 015 wheat straw + 6 cement 020 wheat straw + 6 cement025 wheat straw + 6 cement

(c)

Figure 6 Stress-strain curves of specimens after 14-day curing period (a) Specimens mixed with different wheat straw content (b)Specimens mixed with different cement content (c) Specimens mixed with 6 cement content and different wheat straw content

Advances in Materials Science and Engineering 5

005 010 025020 030000 015Wheat straw content ()

01

02

03

04

05

06

07

08

Axi

al st

ress

σ (M

Pa)

0 cement3 cement

6 cement9 cement

Figure 7 Relationship between wheat straw content and unconfined compressive strength after curing for 14 days

0000 0005 0010 0015 0020 0025 0030 0035 004000

01

02

03

04

05

06

Axi

al st

ress

σ (M

Pa)

Axial strain ε ()

3 days7 days14 days

28 days56 days

Figure 8 Influence of curing periods on unconfined compressive strength of specimens

(a) (b) (c) (d) (e)

Figure 9 Effect of wheat straw content on failure mechanism of specimens (a) 0 wheat straw content (b) 010 wheat straw content (c)015 wheat straw content (d) 020 wheat straw content (e) 025 wheat straw content

6 Advances in Materials Science and Engineering

mixed with 02 wheat straw content and different cementcontent is shown in Figures 13(a)ndash13(d)

In Figures 13(a)ndash13(d) the curve fitting can be expressedby the following expression

p pu minus p0( 1113857 middot 1 minus e(minus αmiddott)

1113872 1113873 + p0 (3)

where p is unconfined compressive strength of specimens tis curing period pu is ultimate unconfined compressivestrength p0 is initial unconfined compressive strength α isthe coefficient related to the shape of curves

In equation (3) using fitting method pu p0 and α canbe obtained based on the data from Figures 12(a)ndash12(d) asshown in Table 5

As shown in Table 5 α is in the range of 014398 to014643 showing that the change of the value of α is verylittle -e mean value for α is 014533 -erefore in order tosimplify equation (1) the value of α is replaced by 0145 andequation (1) can be expressed as

p pu minus p0( 1113857 middot 1 minus e(minus 0145middott)

1113872 1113873 + p0 (4)

331 Initial Unconfined Compressive Strength p0 Inequation (4) p0 and pu can also be obtained based on the datafrom Figures 10(a)ndash10(d) by fitting method as shown inTable 6 Based on the data fromTable 6 the curve fitting for therelationship between p0 and wheat straw content for differentcement content can be obtained as shown in Figure 14

For the curve fitting in Figures 14(a)ndash14(d) it can bedescribed by the following expression

p0 η middot ebmiddotas + p0i (5)

where η is the coefficient for curve growth as is wheatstraw content b is the exponent p0i is initial uncon-fined compressive strength only related to cement con-tent Based on the data from Table 6 η b and p0i inequation (5) can be obtained by fitting method as shownin Table 7

As can be seen from Table 7 the change of η is very littleand the mean value for η is 00017 -erefore equation (5)can be simplified and expressed as

p0 00017 middot ebmiddotas + p0i (6)

Similarly based on the data from Table 6 and equation(6) b and p0i can be obtained by fitting method as shown inTable 8

As shown in Table 8 the change of b is also very little andthe mean value for b is 9356 -erefore in order to simplifyequation (6) b is replaced by 9356 in equation (6) and thenit is expressed as

p0 00017 middot e9356middotas + p0i (7)

Moreover as can be seen from Table 8 p0i is related tocement content Based on the data from Table 8 the rela-tionship between p0i and cement content can also be ob-tained as shown in Figure 15

(a) (b) (c) (d) (e)

Figure 10 Effect of wheat straw content on failure mechanism of specimens mixed with 6 cement content (a) 0 wheat straw content (b)010 wheat straw content (c) 015 wheat straw content (d) 020 wheat straw content (e) 025 wheat straw content

(a) (b) (c) (d) (e)

Figure 11 Effect of curing period on failure mechanism of specimens mixed with 3 cement content and 01 wheat straw content (a) 3days (b) 7 days (c) 14 days (d) 28 days (e) 56 days

Advances in Materials Science and Engineering 7

-e curve fitting for relationship between p0i and cementcontent in Figure 15 can be expressed as

p0i 008014 + 001086 middot ac (8)

where ac is cement content -erefore equation (7) canbe expressed as

p0 00017 middot e9356middotas + 001086 middot ac + 008014 (9)

332 Ultimate Unconfined Compressive Strength pu In thissection equation (4) is also used to determine the value of puHowever in equation (4)p0 can be obtained from equation (9)

according to the cement content and wheat straw contentFurthermore based on the data from Figures 12(a)ndash12(d) pucan be obtained with equation (3) as shown in Table 9

For the curve fitting in Figure 16 it can be described bythe following expression

pu a middot eminus ςmiddotas( ) + pui (10)

where a is the coefficient related to curve growth as is wheatstraw content b is the exponent pui is initial ultimateunconfined compressive strength of specimens only relatedto cement content Similarly a ς and pui in equation (10)can be obtained by fitting method based on the data fromTable 9 as shown in Table 10

0 10 20 30 40 50 60 7000

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing age (day)

0 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(a)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing age (day)

3 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(b)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing age (day)

6 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(c)

00

01

02

03

04

05

06

07Pe

ak st

ress

σ (M

Pa)

0 10 20 30 40 50 60 70Curing age (day)

9 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(d)

Figure 12 Effect of curing periods on unconfined compressive strength of specimens mixed with wheat straws and different cementcontent (a) 0 cement content (b) 3 cement content (c) 6 cement content (d) 9 cement content

8 Advances in Materials Science and Engineering

0 10 20 30 40 50 60 7000

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing aging (day)

0 cement content

(a)

000 10 20 30 40 50 60 70

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing aging (day)

3 cement content

(b)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing aging (day)

6 cement content

(c)

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing aging (day)

9 cement content

(d)

Figure 13 Curve fitting for the relationship between curing periods and unconfined compressive strength of specimens mixed with 02wheat straw and different cement content (a) 0 cement content (b) 3 cement content (c) 6 cement content (d) 9 cement content

Table 5 pu p0 and α in equation (3) obtained by fitting method

Cement content () Wheat straw content () A pu p0 Correlation coefficient (R)

0

000 014588 043154 009152 098592010 014516 044304 009313 098594015 014618 044932 009624 098513020 014544 045447 010006 098573025 014475 046229 010691 098532

3

000 014579 058251 012124 098826010 014551 058510 012383 098837015 014540 058738 012611 098756020 014464 059306 013179 098620025 014476 059871 013744 098922

6

000 014398 073439 015303 098871010 014613 073703 015567 098887015 014558 074029 015893 098998020 014623 074398 016262 098928025 014489 074994 016858 099096

9

000 014483 089900 018327 099765010 014643 090140 018567 099796015 014568 090410 018837 099796020 014456 090841 019268 099864025 014483 091405 019832 099801

Advances in Materials Science and Engineering 9

Table 6 p0 and pu in equation (4) obtained by fitting method

Cement content () Wheat straw content () α pu p0 Correlation coefficient (R)

0

000

0145

042040 008205 098389010 043203 008498 098396015 043892 008708 098338020 044639 009132 098464025 045536 009759 098451

3

000

0145

056306 011459 098765010 057668 011623 098763015 058741 011906 098752020 059589 012309 098607025 061033 012917 098894

6

000

0145

075501 014632 098870010 075883 014825 098885015 076059 015161 098966020 076642 015566 098839025 078146 016166 099062

9

000

0145

093233 018034 099679010 094507 018203 099703015 095207 018589 099711020 095780 018931 099748025 096357 019594 099705

000

002

004

006

008

010

012

014

016

018

020

022

024

026

0080

0085

0090

0095

0100

P 0 (M

Pa)

Wheat straw content as ()

0 cement content

(a)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0110

0115

0120

0125

0130

3 cement content

(b)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0140

0145

0150

0155

0160

0165

0170

6 cement content

(c)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0175

0180

0185

0190

0195

0200

9 cement content

(d)

Figure 14 Curve fitting for the relationship between p0 and wheat straw content for different cement content (a) 0 cement content (b)3 cement content (c) 6 cement content (d) 9 cement content

10 Advances in Materials Science and Engineering

As can be seen from Table 10 a is in the range of 000832to 000861 showing that the change of a is very little -emean value for a is 000849 and the value of a in equation(10) is replaced by 00085 then equation (10) can beexpressed as

pu 00085 middot eminus ξmiddotas( ) + pui (11)

-en based on equation (11) and the data in Table 9 ςand pui can be further obtained by fitting method as shownin Table 11

Figure 17 shows the curve fitting for the relationshipbetween ξ and cement content and the following expressioncan describe the curve fitting

ξ a1 middot eminus b1 middotac( ) + ξ0 (12)

where a1 is the coefficient related to curve growth ac iscement content b1 is the exponent ξ0 is initial value of ξonly related to cement content Based on the data fromTable 11 a1 b1 and ξ0 can be obtained by fitting methodwhich are 1514 0096 and 5002 respectively -ereforeequation (12) can be expressed as

ξ 1514 middot eminus 0096middotac( ) + 5002 (13)

Moreover Figure 18 shows the curve fitting for therelationship between pui and cement content -e followingexpression can describe the fitting curve in Figure 18

pui 00571 middot ac + 040226 (14)

-erefore substituting equations (13) and (14) intoequation (11) it can be expressed as

pu 00085 middot eminus 1514middote minus0096middotac( )+5002( 1113857middotas( 1113857

+ 00571 middot ac + 040226

(15)

p0 and pu in equation (4) are replaced by equations (9) and(15) then equation (4) can be expressed as

p 00085 middot e minus 1514middote minus0096middotac( )+5002( 1113857middotas( + 004624 middot ac + 004624

minus00017 middot e9356middotas

⎛⎝ ⎞⎠

middot 1 minus e(minus 0145middott)

1113872 1113873 + 000165 middot e9356middotas + 001086 middot ac + 008014

(16)

From the published literature [16] ultimate unconfinedcompressive strength increased firstly with adding wheatstraws however with further increasing of wheat strawscontent the ultimate unconfined compressive strength de-creased In test we cannot find the maximum wheat strawscontent and therefore when using equation (16) to predictthe ultimate unconfined compressive strength wheat straws

Table 7 η b and p0i in equation (5) obtained by fitting method

Cement content () Η b p0i Correlation coefficient (R)

0 000176 892416 008035 0999653 000159 910512 011308 0998956 000188 938257 014420 0998449 000167 1008636 017843 099709

Table 8 b and p0i in equation (6) obtained by fitting method

Cement content b p0i Correlation coefficient (R)

0 934882 008053 0999623 924118 011252 0998586 939121 014456 0998329 944322 017848 099709

00 20 40 60 80 100

008

010

012

014

016

018

020

P 0i (

MPa

)

Cement content ()

Figure 15 Curve fitting for the relationship between p0i andcement content

Table 9 pu in equation (3) obtained with equation (4)

Cement content () Wheat straw content() α pu

0

000

0145

042179010 043434015 043685020 044085025 045725

3

000

0145

056437010 057692015 058943020 059343025 061983

6

000

0145

075695010 075950015 076201020 076601025 078241

9

000

0145

092953010 094208015 095459020 095859025 096499

Advances in Materials Science and Engineering 11

content cannot exceed 025 by weight of saline-alkalinesoils In addition when cement content in specimens isgreater than 9 by weight of saline-alkaline soils we cannotperform a series of tests to obtain the influence of cementcontent on ultimate unconfined compressive strength andtherefore in the application of equation (16) cement content

should be less than 9 Moreover for equation (16) derivedfrom the test on specimens with optimum water contentwhen using it to predict the ultimate unconfined com-pressive strength for specimens the range of optimum watercontent for specimens should fall into 127sim145 byweight of saline-alkaline soils

0 cement content

041504200425043004350440044504500455

04650460

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(a)

3 cement content

030010 015 020 025005000Wheat straw content ()

056005650570057505800585059005950600060506100615062006250630

P u (M

Pa)

(b)

0750

0755

0760

0765

0770

0775

0780

0785

0790

6 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(c)

09200925093009350940094509500955096009650970

9 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(d)

Figure 16 Curve fitting for the relationship between pu and wheat straw content for different cement content (a) 0 cement content (b)3 cement content (c) 6 cement content (d) 9 cement content

Table 10 a ς and pui in equation (10) obtained by fitting method

Cement content a ς pui Correlation coefficient (R)

0 000861 639527 041324 0998703 000832 689803 055693 0998376 000857 745161 075670 0998659 000848 832193 091686 099934

Table 11 ς and pui in equation (11) obtained by fitting method

Cement content () a ς pui Correlation coefficient (R)

0

00085

651373 041364 0998693 702611 055628 0998356 768670 074533 0959769 858824 092165 099841

12 Advances in Materials Science and Engineering

34 Validity of Derived Equation (16) for Unconfined Com-pressive Strength of Specimens In order to obtain the reli-ability of derived equation (16) for unconfined compressivestrength of specimens the results from derived equation (16)should be compared with those from tests Based onequation (16) unconfined compressive strength of speci-mens mixed with 6 cement content and 02 wheat strawcontent for different curing periods can be obtained asshown in Table 12 In addition test results for unconfinedcompressive strength of specimens mixed with 6 cementcontent and 02 wheat straw content for different curingperiods are also shown in Table 12

As can be seen from Table 12 most of the deviation forunconfined compression strength falls in the range of260sim300 and the maximum deviation for unconfinedcompression strength can reach 316 when curing period is3 days -erefore compared with the test results the ac-curacy of results from the derived equation (16) is not veryhigh also indicating that equation (16) is only applicable tothe approximate evaluation of unconfined compression

strength of saline-alkaline soils In this paper we onlycompare the test result for specimens with combination ofwheat straw content and cement content already used in thecurrent study When using equation (16) to predict theunconfined compression strength of specimens with anothercombination of wheat straw content and cement contentother than what had been already used in the current studyspecimens should be in the state of maximum densitytherefore compaction tests should be firstly carried out toobtain the optimal moisture content of the specimens

4 Conclusions

In this study a series of tests are conducted to study theeffects of wheat straw and cement on the unconfinedcompression strength of specimens -e effect of wheatstraw and cement inclusions and curing periods on un-confined compression strength is determined -e followingconclusions are derived from these tests

-e inclusion of wheat straw within saline-alkaline soilsand saline-alkaline soils mixed with cement causes an in-crease in unconfined compression strength Increasingwheat straw content can increase the peak axial stress andweaken the brittle behavior of saline-alkaline soils mixedwith cement Moreover unconfined compression strengthof specimens increases with increasing curing periods It isknown that the interface roughness for wheat straw plays animportant role in reinforcing the soil Although it is animportant subject no attempt has yet been made to de-termine the optimum degree of the interface roughness Inaddition based on the data obtained from unconfinedcompression strength test a formula for predicting theunconfined compression strength of specimens related tocement content wheat straw content curing periods and soforth is put forward Compared with test results equation(16) is only applicable to the approximate evaluation ofunconfined compression strength of specimens

In addition in the present study we cannot obtain theinfluence of wheat straw content greater than 025 andorcement content greater than 9 on unconfined compressionstrength of specimens of specimens -erefore the appli-cation scope of equation (16) is limited If more test results ofunconfined compression strength of specimens mixed withwheat straw content greater than 025 andor cementcontent greater than 9 are obtained the application ofequation (16) will be more extensive in predicting the un-confined compression strength of specimens with optimalmoisture content Moreover only unconfined compression

00 20 40 60 80 10050

55

60

65

70

75

80

85

90

Cement content ()

ξ

Figure 17 Curve fitting for the relationship between ξ and cementcontent

00 20 40 60 80 100Cement content ()

10

09

08

07

06

05

04

03

02

01

00

p ui (

MPa

)

Figure 18 Curve fitting for the relationship between pui and ce-ment content

Table 12 Unconfined compression strength obtained from testand calculated value by equation (16)

Curingdays

Calculated value(MPa)

Test result(MPa)

Deviation()

3 0179 0136 3167 0398 0312 27614 0581 0449 29428 0582 0461 26256 0681 0529 286

Advances in Materials Science and Engineering 13

strength tests have been conducted on specimensmixed withwheat straw and cement -erefore investigations should becarried out further through other strength tests like directshear tests triaxial shear tests and so forth to study theinfluence of wheat straw on strength of specimens

Data Availability

-e data used to support the findings of this study are in-cluded within the article

Conflicts of Interest

-e authors declare no conflicts of interest with respect tothe research authorship andor publication of this article

Acknowledgments

-is work was financially supported by National NaturalScience Foundation of China (Grant no 51908430) Doc-toral Scientific Fund Project of Weifang University (Grantno 2017BS14) and Science and Technology Project of High-Tech Zone in Weifang (Grant no 2019KJHM09)

References

[1] R L Michalowski and J Cermak ldquoTriaxial compression ofsand reinforced with fibersrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 129 no 2 pp 125ndash1362003

[2] T Yetimoglu M Inanir and O Esatinanir ldquoA study onbearing capacity of randomly distributed fiber-reinforcedsand fills overlying soft clayrdquo Geotextiles and Geomembranesvol 23 no 2 pp 174ndash183 2005

[3] T Park and S Tan ldquoEnhanced performance of reinforced soilwalls by the inclusion of short fiberrdquo Geotextiles and Geo-membranes vol 23 no 4 pp 348ndash361 2005

[4] C Tang B Shi W Gao F Chen and Y Cai ldquoStrength andmechanical behavior of short polypropylene fiber reinforcedand cement stabilized clayey soilrdquo Geotextiles and Geo-membranes vol 25 no 3 pp 194ndash202 2007

[5] S Salah N Shadi and F Fadi ldquoShear strength of fiber-reinforced sandsrdquo Journal of Geotechnical and Geo-environmental Engineering vol 136 no 3 pp 490ndash499 2010

[6] G A Santiago C Franco N C Consoli and V R BotaroldquoStudy of mechanical behavior of a sand soil reinforced withcuraua treated fibers with asphaltrdquo Materials Science Forumvol 730-732 pp 319ndash324 2012

[7] J Prabakar and R S Sridhar ldquoEffect of random inclusion ofsisal fibre on strength behaviour of soilrdquo Construction andBuilding Materials vol 16 no 2 pp 123ndash131 2002

[8] C Mahipal Singh M Satyendra and M BijayanandaldquoPerformance evaluation of silty sand subgrade reinforcedwith fly ash and fibrerdquoGeotextiles and Geomembranes vol 26no 5 pp 429ndash435 2008

[9] M Bouhicha F Aouissi and S Kenai ldquoPerformance ofcomposite soil reinforced with barley strawrdquo Cement andConcrete Composites vol 27 no 5 pp 617ndash621 2005

[10] N C Consoli M D T Casagrande P D M Prietto andA n -ome ldquoPlate load test on fiber-reinforced soilrdquo Journalof Geotechnical and Geoenvironmental Engineering vol 129no 10 pp 951ndash955 2003

[11] J Yao Experimental Study on Strength Characteristics ofWheat Straw Reinforced soil Changrsquoan University XirsquoanChina 2017

[12] A Adili A Rafig S Giovanni et al ldquoStrength of soil rein-forced with fiber materials (papyrus)rdquo Soil Mechanics andFoundation Engineering vol 48 no 6 pp 241ndash247 2012

[13] Y L Qian ldquoExperimentresearch of mechanical properties ofimproved saline soilrdquo Geotechnical Investigation and Sur-veying vol 5 pp 1ndash4 2003

[14] X S Wang H Q Zhang and M Xue ldquoRoad disease andtreatment in saline soil areardquo Journal of Tongji Universityvol 31 no 10 pp 1178ndash1182 2003

[15] Q LWang Y Chao Y F Liu et al ldquoMechanical properties ofsaline soil under the influence of different factorsrdquo FreseniusEnvironmental Bulletin vol 28 no 2A pp 1366ndash1373 2019

[16] L Wei S X Chai H Z Cai et al ldquoResearch on tensility ofwheat straw for reinforced materialrdquo Rock amp Soil Mechanicsvol 31 no 1 pp 128ndash132 2010

[17] L Wei S X Chai H Z Cai et al ldquoPhysical and mechanicalproperties of wheat straw and unconfined compressivestrength of reinforced inshore saline soil with wheat strawrdquoChina Civil Engineering Journal vol 43 no 3 pp 93ndash982010

[18] M Li S X Chai H P Du et al ldquoReasonable reinforcementposition and shear strength model of reinforced saline soilwith wheat straw and limerdquo Chinese Jourhal of Rock Me-chanics and Engineering vol 29 no sup 2 pp 3923ndash39292010

[19] P Wang S X Chai X Y Wang et al ldquoAnalysis of effectfactors of heavy compaction test for wheat straw-reinforcedsaline soilrdquo Rock and Soil Mechanics vol 32 no 2pp 448ndash452 2011

[20] L Wei S X Chai H Z Cai et al ldquoTriaxial shear strength anddeviatoric stress-strain of saline soils reinforced with wheatstrawsrdquo China Civil Engineering Journal vol 45 no 1pp 109ndash114 2012

[21] H Lu C G Yan X H Yang et al ldquoExperiment on anti-eroding property of reinforced loess with wheat strawrdquoJournal of Changrsquoan University (Natural Science Edition)vol 37 no 1 pp 24ndash32 2017

[22] J B Hao X MWei J Yao et al ldquoStrength characteristics andmesostructure of wheat straw einforced soilrdquo Journal of TongjiUniversity (Natural Science) vol 47 no 6 pp 764ndash831 2019

[23] GB50007-2011 Code for Design of Building foundationMinistry of Housing and Urban-Rural Development BeijingChina 2012

[24] JTG D30-2015 Specifications for Design of Highway Sub-grades China Communications Publishing amp Media Man-agement Co Ltd Beijing China 2016

[25] GBT 50123-1999 Standard for Soil Test Method Ministry ofConstruction Beijing China 2000

14 Advances in Materials Science and Engineering

of the bottom of specimens occurs and it does not obviouslyexhibit the shear plane When the curing period is 14 daysthere are two simultaneous failure modes in specimens asshown in Figure 11(c) However as can be seen fromFigures 11(d) and 11(e) when the curing period is greaterthan 14 days only shear plane failure occurs in specimensDuring the unconfined compressive strength tests we alsofind that the increasing of curing periods can improve thebrittle behavior of specimens and the trend for influence ofcuring periods on the brittle behavior of specimens is similarto that shown in Figure 8

33 Prediction for Unconfined Compressive Strength ofSpecimens Mixed with Wheat Straws and Cement As

discussed above the factors affecting unconfined com-pressive strength of specimens include wheat straw contentcement content and curing periods In this section a for-mula that can predict unconfined compressive strength ofspecimens is put forward based on the results from un-confined compressive strength test on saline-alkaline soilsmixed with wheat straws and cement Figures 12(a)ndash12(d)show the increasing of unconfined compressive strength ofspecimens with curing periods

As can be seen from Figures 12(a)ndash12(d) when thespecimens have the same cement content unconfinedcompressive strength of specimen increases with increasingwheat straw content Based on the data from Figures 12(a)ndash12(d) the curve fitting for the relationship between curingperiod and unconfined compressive strength of specimens

00 10 20 30 40 50 60 70 80 90000

002

004

006

008

010

012

014

016

Axial strain ε ()

Axi

al st

ress

σ (M

Pa)

0 wheat straw010 wheat straw 015 wheat straw

020 wheat straw025 wheat straw

(a)

00 10 20 30 40 50 60 70Axial strain ε ()

00

01

02

03

04

05

06

Axi

al st

ress

σ (M

Pa)

00 cement30 cement

60 cement90 cement

(b)

00 10 20 30 40 50 60Axial strain ε ()

00

01

02

03

04

05

06

Axi

al st

ress

σ (M

Pa)

0 wheat straw + 6 cement010 wheat straw + 6 cement 015 wheat straw + 6 cement 020 wheat straw + 6 cement025 wheat straw + 6 cement

(c)

Figure 6 Stress-strain curves of specimens after 14-day curing period (a) Specimens mixed with different wheat straw content (b)Specimens mixed with different cement content (c) Specimens mixed with 6 cement content and different wheat straw content

Advances in Materials Science and Engineering 5

005 010 025020 030000 015Wheat straw content ()

01

02

03

04

05

06

07

08

Axi

al st

ress

σ (M

Pa)

0 cement3 cement

6 cement9 cement

Figure 7 Relationship between wheat straw content and unconfined compressive strength after curing for 14 days

0000 0005 0010 0015 0020 0025 0030 0035 004000

01

02

03

04

05

06

Axi

al st

ress

σ (M

Pa)

Axial strain ε ()

3 days7 days14 days

28 days56 days

Figure 8 Influence of curing periods on unconfined compressive strength of specimens

(a) (b) (c) (d) (e)

Figure 9 Effect of wheat straw content on failure mechanism of specimens (a) 0 wheat straw content (b) 010 wheat straw content (c)015 wheat straw content (d) 020 wheat straw content (e) 025 wheat straw content

6 Advances in Materials Science and Engineering

mixed with 02 wheat straw content and different cementcontent is shown in Figures 13(a)ndash13(d)

In Figures 13(a)ndash13(d) the curve fitting can be expressedby the following expression

p pu minus p0( 1113857 middot 1 minus e(minus αmiddott)

1113872 1113873 + p0 (3)

where p is unconfined compressive strength of specimens tis curing period pu is ultimate unconfined compressivestrength p0 is initial unconfined compressive strength α isthe coefficient related to the shape of curves

In equation (3) using fitting method pu p0 and α canbe obtained based on the data from Figures 12(a)ndash12(d) asshown in Table 5

As shown in Table 5 α is in the range of 014398 to014643 showing that the change of the value of α is verylittle -e mean value for α is 014533 -erefore in order tosimplify equation (1) the value of α is replaced by 0145 andequation (1) can be expressed as

p pu minus p0( 1113857 middot 1 minus e(minus 0145middott)

1113872 1113873 + p0 (4)

331 Initial Unconfined Compressive Strength p0 Inequation (4) p0 and pu can also be obtained based on the datafrom Figures 10(a)ndash10(d) by fitting method as shown inTable 6 Based on the data fromTable 6 the curve fitting for therelationship between p0 and wheat straw content for differentcement content can be obtained as shown in Figure 14

For the curve fitting in Figures 14(a)ndash14(d) it can bedescribed by the following expression

p0 η middot ebmiddotas + p0i (5)

where η is the coefficient for curve growth as is wheatstraw content b is the exponent p0i is initial uncon-fined compressive strength only related to cement con-tent Based on the data from Table 6 η b and p0i inequation (5) can be obtained by fitting method as shownin Table 7

As can be seen from Table 7 the change of η is very littleand the mean value for η is 00017 -erefore equation (5)can be simplified and expressed as

p0 00017 middot ebmiddotas + p0i (6)

Similarly based on the data from Table 6 and equation(6) b and p0i can be obtained by fitting method as shown inTable 8

As shown in Table 8 the change of b is also very little andthe mean value for b is 9356 -erefore in order to simplifyequation (6) b is replaced by 9356 in equation (6) and thenit is expressed as

p0 00017 middot e9356middotas + p0i (7)

Moreover as can be seen from Table 8 p0i is related tocement content Based on the data from Table 8 the rela-tionship between p0i and cement content can also be ob-tained as shown in Figure 15

(a) (b) (c) (d) (e)

Figure 10 Effect of wheat straw content on failure mechanism of specimens mixed with 6 cement content (a) 0 wheat straw content (b)010 wheat straw content (c) 015 wheat straw content (d) 020 wheat straw content (e) 025 wheat straw content

(a) (b) (c) (d) (e)

Figure 11 Effect of curing period on failure mechanism of specimens mixed with 3 cement content and 01 wheat straw content (a) 3days (b) 7 days (c) 14 days (d) 28 days (e) 56 days

Advances in Materials Science and Engineering 7

-e curve fitting for relationship between p0i and cementcontent in Figure 15 can be expressed as

p0i 008014 + 001086 middot ac (8)

where ac is cement content -erefore equation (7) canbe expressed as

p0 00017 middot e9356middotas + 001086 middot ac + 008014 (9)

332 Ultimate Unconfined Compressive Strength pu In thissection equation (4) is also used to determine the value of puHowever in equation (4)p0 can be obtained from equation (9)

according to the cement content and wheat straw contentFurthermore based on the data from Figures 12(a)ndash12(d) pucan be obtained with equation (3) as shown in Table 9

For the curve fitting in Figure 16 it can be described bythe following expression

pu a middot eminus ςmiddotas( ) + pui (10)

where a is the coefficient related to curve growth as is wheatstraw content b is the exponent pui is initial ultimateunconfined compressive strength of specimens only relatedto cement content Similarly a ς and pui in equation (10)can be obtained by fitting method based on the data fromTable 9 as shown in Table 10

0 10 20 30 40 50 60 7000

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing age (day)

0 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(a)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing age (day)

3 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(b)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing age (day)

6 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(c)

00

01

02

03

04

05

06

07Pe

ak st

ress

σ (M

Pa)

0 10 20 30 40 50 60 70Curing age (day)

9 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(d)

Figure 12 Effect of curing periods on unconfined compressive strength of specimens mixed with wheat straws and different cementcontent (a) 0 cement content (b) 3 cement content (c) 6 cement content (d) 9 cement content

8 Advances in Materials Science and Engineering

0 10 20 30 40 50 60 7000

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing aging (day)

0 cement content

(a)

000 10 20 30 40 50 60 70

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing aging (day)

3 cement content

(b)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing aging (day)

6 cement content

(c)

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing aging (day)

9 cement content

(d)

Figure 13 Curve fitting for the relationship between curing periods and unconfined compressive strength of specimens mixed with 02wheat straw and different cement content (a) 0 cement content (b) 3 cement content (c) 6 cement content (d) 9 cement content

Table 5 pu p0 and α in equation (3) obtained by fitting method

Cement content () Wheat straw content () A pu p0 Correlation coefficient (R)

0

000 014588 043154 009152 098592010 014516 044304 009313 098594015 014618 044932 009624 098513020 014544 045447 010006 098573025 014475 046229 010691 098532

3

000 014579 058251 012124 098826010 014551 058510 012383 098837015 014540 058738 012611 098756020 014464 059306 013179 098620025 014476 059871 013744 098922

6

000 014398 073439 015303 098871010 014613 073703 015567 098887015 014558 074029 015893 098998020 014623 074398 016262 098928025 014489 074994 016858 099096

9

000 014483 089900 018327 099765010 014643 090140 018567 099796015 014568 090410 018837 099796020 014456 090841 019268 099864025 014483 091405 019832 099801

Advances in Materials Science and Engineering 9

Table 6 p0 and pu in equation (4) obtained by fitting method

Cement content () Wheat straw content () α pu p0 Correlation coefficient (R)

0

000

0145

042040 008205 098389010 043203 008498 098396015 043892 008708 098338020 044639 009132 098464025 045536 009759 098451

3

000

0145

056306 011459 098765010 057668 011623 098763015 058741 011906 098752020 059589 012309 098607025 061033 012917 098894

6

000

0145

075501 014632 098870010 075883 014825 098885015 076059 015161 098966020 076642 015566 098839025 078146 016166 099062

9

000

0145

093233 018034 099679010 094507 018203 099703015 095207 018589 099711020 095780 018931 099748025 096357 019594 099705

000

002

004

006

008

010

012

014

016

018

020

022

024

026

0080

0085

0090

0095

0100

P 0 (M

Pa)

Wheat straw content as ()

0 cement content

(a)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0110

0115

0120

0125

0130

3 cement content

(b)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0140

0145

0150

0155

0160

0165

0170

6 cement content

(c)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0175

0180

0185

0190

0195

0200

9 cement content

(d)

Figure 14 Curve fitting for the relationship between p0 and wheat straw content for different cement content (a) 0 cement content (b)3 cement content (c) 6 cement content (d) 9 cement content

10 Advances in Materials Science and Engineering

As can be seen from Table 10 a is in the range of 000832to 000861 showing that the change of a is very little -emean value for a is 000849 and the value of a in equation(10) is replaced by 00085 then equation (10) can beexpressed as

pu 00085 middot eminus ξmiddotas( ) + pui (11)

-en based on equation (11) and the data in Table 9 ςand pui can be further obtained by fitting method as shownin Table 11

Figure 17 shows the curve fitting for the relationshipbetween ξ and cement content and the following expressioncan describe the curve fitting

ξ a1 middot eminus b1 middotac( ) + ξ0 (12)

where a1 is the coefficient related to curve growth ac iscement content b1 is the exponent ξ0 is initial value of ξonly related to cement content Based on the data fromTable 11 a1 b1 and ξ0 can be obtained by fitting methodwhich are 1514 0096 and 5002 respectively -ereforeequation (12) can be expressed as

ξ 1514 middot eminus 0096middotac( ) + 5002 (13)

Moreover Figure 18 shows the curve fitting for therelationship between pui and cement content -e followingexpression can describe the fitting curve in Figure 18

pui 00571 middot ac + 040226 (14)

-erefore substituting equations (13) and (14) intoequation (11) it can be expressed as

pu 00085 middot eminus 1514middote minus0096middotac( )+5002( 1113857middotas( 1113857

+ 00571 middot ac + 040226

(15)

p0 and pu in equation (4) are replaced by equations (9) and(15) then equation (4) can be expressed as

p 00085 middot e minus 1514middote minus0096middotac( )+5002( 1113857middotas( + 004624 middot ac + 004624

minus00017 middot e9356middotas

⎛⎝ ⎞⎠

middot 1 minus e(minus 0145middott)

1113872 1113873 + 000165 middot e9356middotas + 001086 middot ac + 008014

(16)

From the published literature [16] ultimate unconfinedcompressive strength increased firstly with adding wheatstraws however with further increasing of wheat strawscontent the ultimate unconfined compressive strength de-creased In test we cannot find the maximum wheat strawscontent and therefore when using equation (16) to predictthe ultimate unconfined compressive strength wheat straws

Table 7 η b and p0i in equation (5) obtained by fitting method

Cement content () Η b p0i Correlation coefficient (R)

0 000176 892416 008035 0999653 000159 910512 011308 0998956 000188 938257 014420 0998449 000167 1008636 017843 099709

Table 8 b and p0i in equation (6) obtained by fitting method

Cement content b p0i Correlation coefficient (R)

0 934882 008053 0999623 924118 011252 0998586 939121 014456 0998329 944322 017848 099709

00 20 40 60 80 100

008

010

012

014

016

018

020

P 0i (

MPa

)

Cement content ()

Figure 15 Curve fitting for the relationship between p0i andcement content

Table 9 pu in equation (3) obtained with equation (4)

Cement content () Wheat straw content() α pu

0

000

0145

042179010 043434015 043685020 044085025 045725

3

000

0145

056437010 057692015 058943020 059343025 061983

6

000

0145

075695010 075950015 076201020 076601025 078241

9

000

0145

092953010 094208015 095459020 095859025 096499

Advances in Materials Science and Engineering 11

content cannot exceed 025 by weight of saline-alkalinesoils In addition when cement content in specimens isgreater than 9 by weight of saline-alkaline soils we cannotperform a series of tests to obtain the influence of cementcontent on ultimate unconfined compressive strength andtherefore in the application of equation (16) cement content

should be less than 9 Moreover for equation (16) derivedfrom the test on specimens with optimum water contentwhen using it to predict the ultimate unconfined com-pressive strength for specimens the range of optimum watercontent for specimens should fall into 127sim145 byweight of saline-alkaline soils

0 cement content

041504200425043004350440044504500455

04650460

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(a)

3 cement content

030010 015 020 025005000Wheat straw content ()

056005650570057505800585059005950600060506100615062006250630

P u (M

Pa)

(b)

0750

0755

0760

0765

0770

0775

0780

0785

0790

6 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(c)

09200925093009350940094509500955096009650970

9 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(d)

Figure 16 Curve fitting for the relationship between pu and wheat straw content for different cement content (a) 0 cement content (b)3 cement content (c) 6 cement content (d) 9 cement content

Table 10 a ς and pui in equation (10) obtained by fitting method

Cement content a ς pui Correlation coefficient (R)

0 000861 639527 041324 0998703 000832 689803 055693 0998376 000857 745161 075670 0998659 000848 832193 091686 099934

Table 11 ς and pui in equation (11) obtained by fitting method

Cement content () a ς pui Correlation coefficient (R)

0

00085

651373 041364 0998693 702611 055628 0998356 768670 074533 0959769 858824 092165 099841

12 Advances in Materials Science and Engineering

34 Validity of Derived Equation (16) for Unconfined Com-pressive Strength of Specimens In order to obtain the reli-ability of derived equation (16) for unconfined compressivestrength of specimens the results from derived equation (16)should be compared with those from tests Based onequation (16) unconfined compressive strength of speci-mens mixed with 6 cement content and 02 wheat strawcontent for different curing periods can be obtained asshown in Table 12 In addition test results for unconfinedcompressive strength of specimens mixed with 6 cementcontent and 02 wheat straw content for different curingperiods are also shown in Table 12

As can be seen from Table 12 most of the deviation forunconfined compression strength falls in the range of260sim300 and the maximum deviation for unconfinedcompression strength can reach 316 when curing period is3 days -erefore compared with the test results the ac-curacy of results from the derived equation (16) is not veryhigh also indicating that equation (16) is only applicable tothe approximate evaluation of unconfined compression

strength of saline-alkaline soils In this paper we onlycompare the test result for specimens with combination ofwheat straw content and cement content already used in thecurrent study When using equation (16) to predict theunconfined compression strength of specimens with anothercombination of wheat straw content and cement contentother than what had been already used in the current studyspecimens should be in the state of maximum densitytherefore compaction tests should be firstly carried out toobtain the optimal moisture content of the specimens

4 Conclusions

In this study a series of tests are conducted to study theeffects of wheat straw and cement on the unconfinedcompression strength of specimens -e effect of wheatstraw and cement inclusions and curing periods on un-confined compression strength is determined -e followingconclusions are derived from these tests

-e inclusion of wheat straw within saline-alkaline soilsand saline-alkaline soils mixed with cement causes an in-crease in unconfined compression strength Increasingwheat straw content can increase the peak axial stress andweaken the brittle behavior of saline-alkaline soils mixedwith cement Moreover unconfined compression strengthof specimens increases with increasing curing periods It isknown that the interface roughness for wheat straw plays animportant role in reinforcing the soil Although it is animportant subject no attempt has yet been made to de-termine the optimum degree of the interface roughness Inaddition based on the data obtained from unconfinedcompression strength test a formula for predicting theunconfined compression strength of specimens related tocement content wheat straw content curing periods and soforth is put forward Compared with test results equation(16) is only applicable to the approximate evaluation ofunconfined compression strength of specimens

In addition in the present study we cannot obtain theinfluence of wheat straw content greater than 025 andorcement content greater than 9 on unconfined compressionstrength of specimens of specimens -erefore the appli-cation scope of equation (16) is limited If more test results ofunconfined compression strength of specimens mixed withwheat straw content greater than 025 andor cementcontent greater than 9 are obtained the application ofequation (16) will be more extensive in predicting the un-confined compression strength of specimens with optimalmoisture content Moreover only unconfined compression

00 20 40 60 80 10050

55

60

65

70

75

80

85

90

Cement content ()

ξ

Figure 17 Curve fitting for the relationship between ξ and cementcontent

00 20 40 60 80 100Cement content ()

10

09

08

07

06

05

04

03

02

01

00

p ui (

MPa

)

Figure 18 Curve fitting for the relationship between pui and ce-ment content

Table 12 Unconfined compression strength obtained from testand calculated value by equation (16)

Curingdays

Calculated value(MPa)

Test result(MPa)

Deviation()

3 0179 0136 3167 0398 0312 27614 0581 0449 29428 0582 0461 26256 0681 0529 286

Advances in Materials Science and Engineering 13

strength tests have been conducted on specimensmixed withwheat straw and cement -erefore investigations should becarried out further through other strength tests like directshear tests triaxial shear tests and so forth to study theinfluence of wheat straw on strength of specimens

Data Availability

-e data used to support the findings of this study are in-cluded within the article

Conflicts of Interest

-e authors declare no conflicts of interest with respect tothe research authorship andor publication of this article

Acknowledgments

-is work was financially supported by National NaturalScience Foundation of China (Grant no 51908430) Doc-toral Scientific Fund Project of Weifang University (Grantno 2017BS14) and Science and Technology Project of High-Tech Zone in Weifang (Grant no 2019KJHM09)

References

[1] R L Michalowski and J Cermak ldquoTriaxial compression ofsand reinforced with fibersrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 129 no 2 pp 125ndash1362003

[2] T Yetimoglu M Inanir and O Esatinanir ldquoA study onbearing capacity of randomly distributed fiber-reinforcedsand fills overlying soft clayrdquo Geotextiles and Geomembranesvol 23 no 2 pp 174ndash183 2005

[3] T Park and S Tan ldquoEnhanced performance of reinforced soilwalls by the inclusion of short fiberrdquo Geotextiles and Geo-membranes vol 23 no 4 pp 348ndash361 2005

[4] C Tang B Shi W Gao F Chen and Y Cai ldquoStrength andmechanical behavior of short polypropylene fiber reinforcedand cement stabilized clayey soilrdquo Geotextiles and Geo-membranes vol 25 no 3 pp 194ndash202 2007

[5] S Salah N Shadi and F Fadi ldquoShear strength of fiber-reinforced sandsrdquo Journal of Geotechnical and Geo-environmental Engineering vol 136 no 3 pp 490ndash499 2010

[6] G A Santiago C Franco N C Consoli and V R BotaroldquoStudy of mechanical behavior of a sand soil reinforced withcuraua treated fibers with asphaltrdquo Materials Science Forumvol 730-732 pp 319ndash324 2012

[7] J Prabakar and R S Sridhar ldquoEffect of random inclusion ofsisal fibre on strength behaviour of soilrdquo Construction andBuilding Materials vol 16 no 2 pp 123ndash131 2002

[8] C Mahipal Singh M Satyendra and M BijayanandaldquoPerformance evaluation of silty sand subgrade reinforcedwith fly ash and fibrerdquoGeotextiles and Geomembranes vol 26no 5 pp 429ndash435 2008

[9] M Bouhicha F Aouissi and S Kenai ldquoPerformance ofcomposite soil reinforced with barley strawrdquo Cement andConcrete Composites vol 27 no 5 pp 617ndash621 2005

[10] N C Consoli M D T Casagrande P D M Prietto andA n -ome ldquoPlate load test on fiber-reinforced soilrdquo Journalof Geotechnical and Geoenvironmental Engineering vol 129no 10 pp 951ndash955 2003

[11] J Yao Experimental Study on Strength Characteristics ofWheat Straw Reinforced soil Changrsquoan University XirsquoanChina 2017

[12] A Adili A Rafig S Giovanni et al ldquoStrength of soil rein-forced with fiber materials (papyrus)rdquo Soil Mechanics andFoundation Engineering vol 48 no 6 pp 241ndash247 2012

[13] Y L Qian ldquoExperimentresearch of mechanical properties ofimproved saline soilrdquo Geotechnical Investigation and Sur-veying vol 5 pp 1ndash4 2003

[14] X S Wang H Q Zhang and M Xue ldquoRoad disease andtreatment in saline soil areardquo Journal of Tongji Universityvol 31 no 10 pp 1178ndash1182 2003

[15] Q LWang Y Chao Y F Liu et al ldquoMechanical properties ofsaline soil under the influence of different factorsrdquo FreseniusEnvironmental Bulletin vol 28 no 2A pp 1366ndash1373 2019

[16] L Wei S X Chai H Z Cai et al ldquoResearch on tensility ofwheat straw for reinforced materialrdquo Rock amp Soil Mechanicsvol 31 no 1 pp 128ndash132 2010

[17] L Wei S X Chai H Z Cai et al ldquoPhysical and mechanicalproperties of wheat straw and unconfined compressivestrength of reinforced inshore saline soil with wheat strawrdquoChina Civil Engineering Journal vol 43 no 3 pp 93ndash982010

[18] M Li S X Chai H P Du et al ldquoReasonable reinforcementposition and shear strength model of reinforced saline soilwith wheat straw and limerdquo Chinese Jourhal of Rock Me-chanics and Engineering vol 29 no sup 2 pp 3923ndash39292010

[19] P Wang S X Chai X Y Wang et al ldquoAnalysis of effectfactors of heavy compaction test for wheat straw-reinforcedsaline soilrdquo Rock and Soil Mechanics vol 32 no 2pp 448ndash452 2011

[20] L Wei S X Chai H Z Cai et al ldquoTriaxial shear strength anddeviatoric stress-strain of saline soils reinforced with wheatstrawsrdquo China Civil Engineering Journal vol 45 no 1pp 109ndash114 2012

[21] H Lu C G Yan X H Yang et al ldquoExperiment on anti-eroding property of reinforced loess with wheat strawrdquoJournal of Changrsquoan University (Natural Science Edition)vol 37 no 1 pp 24ndash32 2017

[22] J B Hao X MWei J Yao et al ldquoStrength characteristics andmesostructure of wheat straw einforced soilrdquo Journal of TongjiUniversity (Natural Science) vol 47 no 6 pp 764ndash831 2019

[23] GB50007-2011 Code for Design of Building foundationMinistry of Housing and Urban-Rural Development BeijingChina 2012

[24] JTG D30-2015 Specifications for Design of Highway Sub-grades China Communications Publishing amp Media Man-agement Co Ltd Beijing China 2016

[25] GBT 50123-1999 Standard for Soil Test Method Ministry ofConstruction Beijing China 2000

14 Advances in Materials Science and Engineering

005 010 025020 030000 015Wheat straw content ()

01

02

03

04

05

06

07

08

Axi

al st

ress

σ (M

Pa)

0 cement3 cement

6 cement9 cement

Figure 7 Relationship between wheat straw content and unconfined compressive strength after curing for 14 days

0000 0005 0010 0015 0020 0025 0030 0035 004000

01

02

03

04

05

06

Axi

al st

ress

σ (M

Pa)

Axial strain ε ()

3 days7 days14 days

28 days56 days

Figure 8 Influence of curing periods on unconfined compressive strength of specimens

(a) (b) (c) (d) (e)

Figure 9 Effect of wheat straw content on failure mechanism of specimens (a) 0 wheat straw content (b) 010 wheat straw content (c)015 wheat straw content (d) 020 wheat straw content (e) 025 wheat straw content

6 Advances in Materials Science and Engineering

mixed with 02 wheat straw content and different cementcontent is shown in Figures 13(a)ndash13(d)

In Figures 13(a)ndash13(d) the curve fitting can be expressedby the following expression

p pu minus p0( 1113857 middot 1 minus e(minus αmiddott)

1113872 1113873 + p0 (3)

where p is unconfined compressive strength of specimens tis curing period pu is ultimate unconfined compressivestrength p0 is initial unconfined compressive strength α isthe coefficient related to the shape of curves

In equation (3) using fitting method pu p0 and α canbe obtained based on the data from Figures 12(a)ndash12(d) asshown in Table 5

As shown in Table 5 α is in the range of 014398 to014643 showing that the change of the value of α is verylittle -e mean value for α is 014533 -erefore in order tosimplify equation (1) the value of α is replaced by 0145 andequation (1) can be expressed as

p pu minus p0( 1113857 middot 1 minus e(minus 0145middott)

1113872 1113873 + p0 (4)

331 Initial Unconfined Compressive Strength p0 Inequation (4) p0 and pu can also be obtained based on the datafrom Figures 10(a)ndash10(d) by fitting method as shown inTable 6 Based on the data fromTable 6 the curve fitting for therelationship between p0 and wheat straw content for differentcement content can be obtained as shown in Figure 14

For the curve fitting in Figures 14(a)ndash14(d) it can bedescribed by the following expression

p0 η middot ebmiddotas + p0i (5)

where η is the coefficient for curve growth as is wheatstraw content b is the exponent p0i is initial uncon-fined compressive strength only related to cement con-tent Based on the data from Table 6 η b and p0i inequation (5) can be obtained by fitting method as shownin Table 7

As can be seen from Table 7 the change of η is very littleand the mean value for η is 00017 -erefore equation (5)can be simplified and expressed as

p0 00017 middot ebmiddotas + p0i (6)

Similarly based on the data from Table 6 and equation(6) b and p0i can be obtained by fitting method as shown inTable 8

As shown in Table 8 the change of b is also very little andthe mean value for b is 9356 -erefore in order to simplifyequation (6) b is replaced by 9356 in equation (6) and thenit is expressed as

p0 00017 middot e9356middotas + p0i (7)

Moreover as can be seen from Table 8 p0i is related tocement content Based on the data from Table 8 the rela-tionship between p0i and cement content can also be ob-tained as shown in Figure 15

(a) (b) (c) (d) (e)

Figure 10 Effect of wheat straw content on failure mechanism of specimens mixed with 6 cement content (a) 0 wheat straw content (b)010 wheat straw content (c) 015 wheat straw content (d) 020 wheat straw content (e) 025 wheat straw content

(a) (b) (c) (d) (e)

Figure 11 Effect of curing period on failure mechanism of specimens mixed with 3 cement content and 01 wheat straw content (a) 3days (b) 7 days (c) 14 days (d) 28 days (e) 56 days

Advances in Materials Science and Engineering 7

-e curve fitting for relationship between p0i and cementcontent in Figure 15 can be expressed as

p0i 008014 + 001086 middot ac (8)

where ac is cement content -erefore equation (7) canbe expressed as

p0 00017 middot e9356middotas + 001086 middot ac + 008014 (9)

332 Ultimate Unconfined Compressive Strength pu In thissection equation (4) is also used to determine the value of puHowever in equation (4)p0 can be obtained from equation (9)

according to the cement content and wheat straw contentFurthermore based on the data from Figures 12(a)ndash12(d) pucan be obtained with equation (3) as shown in Table 9

For the curve fitting in Figure 16 it can be described bythe following expression

pu a middot eminus ςmiddotas( ) + pui (10)

where a is the coefficient related to curve growth as is wheatstraw content b is the exponent pui is initial ultimateunconfined compressive strength of specimens only relatedto cement content Similarly a ς and pui in equation (10)can be obtained by fitting method based on the data fromTable 9 as shown in Table 10

0 10 20 30 40 50 60 7000

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing age (day)

0 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(a)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing age (day)

3 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(b)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing age (day)

6 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(c)

00

01

02

03

04

05

06

07Pe

ak st

ress

σ (M

Pa)

0 10 20 30 40 50 60 70Curing age (day)

9 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(d)

Figure 12 Effect of curing periods on unconfined compressive strength of specimens mixed with wheat straws and different cementcontent (a) 0 cement content (b) 3 cement content (c) 6 cement content (d) 9 cement content

8 Advances in Materials Science and Engineering

0 10 20 30 40 50 60 7000

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing aging (day)

0 cement content

(a)

000 10 20 30 40 50 60 70

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing aging (day)

3 cement content

(b)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing aging (day)

6 cement content

(c)

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing aging (day)

9 cement content

(d)

Figure 13 Curve fitting for the relationship between curing periods and unconfined compressive strength of specimens mixed with 02wheat straw and different cement content (a) 0 cement content (b) 3 cement content (c) 6 cement content (d) 9 cement content

Table 5 pu p0 and α in equation (3) obtained by fitting method

Cement content () Wheat straw content () A pu p0 Correlation coefficient (R)

0

000 014588 043154 009152 098592010 014516 044304 009313 098594015 014618 044932 009624 098513020 014544 045447 010006 098573025 014475 046229 010691 098532

3

000 014579 058251 012124 098826010 014551 058510 012383 098837015 014540 058738 012611 098756020 014464 059306 013179 098620025 014476 059871 013744 098922

6

000 014398 073439 015303 098871010 014613 073703 015567 098887015 014558 074029 015893 098998020 014623 074398 016262 098928025 014489 074994 016858 099096

9

000 014483 089900 018327 099765010 014643 090140 018567 099796015 014568 090410 018837 099796020 014456 090841 019268 099864025 014483 091405 019832 099801

Advances in Materials Science and Engineering 9

Table 6 p0 and pu in equation (4) obtained by fitting method

Cement content () Wheat straw content () α pu p0 Correlation coefficient (R)

0

000

0145

042040 008205 098389010 043203 008498 098396015 043892 008708 098338020 044639 009132 098464025 045536 009759 098451

3

000

0145

056306 011459 098765010 057668 011623 098763015 058741 011906 098752020 059589 012309 098607025 061033 012917 098894

6

000

0145

075501 014632 098870010 075883 014825 098885015 076059 015161 098966020 076642 015566 098839025 078146 016166 099062

9

000

0145

093233 018034 099679010 094507 018203 099703015 095207 018589 099711020 095780 018931 099748025 096357 019594 099705

000

002

004

006

008

010

012

014

016

018

020

022

024

026

0080

0085

0090

0095

0100

P 0 (M

Pa)

Wheat straw content as ()

0 cement content

(a)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0110

0115

0120

0125

0130

3 cement content

(b)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0140

0145

0150

0155

0160

0165

0170

6 cement content

(c)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0175

0180

0185

0190

0195

0200

9 cement content

(d)

Figure 14 Curve fitting for the relationship between p0 and wheat straw content for different cement content (a) 0 cement content (b)3 cement content (c) 6 cement content (d) 9 cement content

10 Advances in Materials Science and Engineering

As can be seen from Table 10 a is in the range of 000832to 000861 showing that the change of a is very little -emean value for a is 000849 and the value of a in equation(10) is replaced by 00085 then equation (10) can beexpressed as

pu 00085 middot eminus ξmiddotas( ) + pui (11)

-en based on equation (11) and the data in Table 9 ςand pui can be further obtained by fitting method as shownin Table 11

Figure 17 shows the curve fitting for the relationshipbetween ξ and cement content and the following expressioncan describe the curve fitting

ξ a1 middot eminus b1 middotac( ) + ξ0 (12)

where a1 is the coefficient related to curve growth ac iscement content b1 is the exponent ξ0 is initial value of ξonly related to cement content Based on the data fromTable 11 a1 b1 and ξ0 can be obtained by fitting methodwhich are 1514 0096 and 5002 respectively -ereforeequation (12) can be expressed as

ξ 1514 middot eminus 0096middotac( ) + 5002 (13)

Moreover Figure 18 shows the curve fitting for therelationship between pui and cement content -e followingexpression can describe the fitting curve in Figure 18

pui 00571 middot ac + 040226 (14)

-erefore substituting equations (13) and (14) intoequation (11) it can be expressed as

pu 00085 middot eminus 1514middote minus0096middotac( )+5002( 1113857middotas( 1113857

+ 00571 middot ac + 040226

(15)

p0 and pu in equation (4) are replaced by equations (9) and(15) then equation (4) can be expressed as

p 00085 middot e minus 1514middote minus0096middotac( )+5002( 1113857middotas( + 004624 middot ac + 004624

minus00017 middot e9356middotas

⎛⎝ ⎞⎠

middot 1 minus e(minus 0145middott)

1113872 1113873 + 000165 middot e9356middotas + 001086 middot ac + 008014

(16)

From the published literature [16] ultimate unconfinedcompressive strength increased firstly with adding wheatstraws however with further increasing of wheat strawscontent the ultimate unconfined compressive strength de-creased In test we cannot find the maximum wheat strawscontent and therefore when using equation (16) to predictthe ultimate unconfined compressive strength wheat straws

Table 7 η b and p0i in equation (5) obtained by fitting method

Cement content () Η b p0i Correlation coefficient (R)

0 000176 892416 008035 0999653 000159 910512 011308 0998956 000188 938257 014420 0998449 000167 1008636 017843 099709

Table 8 b and p0i in equation (6) obtained by fitting method

Cement content b p0i Correlation coefficient (R)

0 934882 008053 0999623 924118 011252 0998586 939121 014456 0998329 944322 017848 099709

00 20 40 60 80 100

008

010

012

014

016

018

020

P 0i (

MPa

)

Cement content ()

Figure 15 Curve fitting for the relationship between p0i andcement content

Table 9 pu in equation (3) obtained with equation (4)

Cement content () Wheat straw content() α pu

0

000

0145

042179010 043434015 043685020 044085025 045725

3

000

0145

056437010 057692015 058943020 059343025 061983

6

000

0145

075695010 075950015 076201020 076601025 078241

9

000

0145

092953010 094208015 095459020 095859025 096499

Advances in Materials Science and Engineering 11

content cannot exceed 025 by weight of saline-alkalinesoils In addition when cement content in specimens isgreater than 9 by weight of saline-alkaline soils we cannotperform a series of tests to obtain the influence of cementcontent on ultimate unconfined compressive strength andtherefore in the application of equation (16) cement content

should be less than 9 Moreover for equation (16) derivedfrom the test on specimens with optimum water contentwhen using it to predict the ultimate unconfined com-pressive strength for specimens the range of optimum watercontent for specimens should fall into 127sim145 byweight of saline-alkaline soils

0 cement content

041504200425043004350440044504500455

04650460

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(a)

3 cement content

030010 015 020 025005000Wheat straw content ()

056005650570057505800585059005950600060506100615062006250630

P u (M

Pa)

(b)

0750

0755

0760

0765

0770

0775

0780

0785

0790

6 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(c)

09200925093009350940094509500955096009650970

9 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(d)

Figure 16 Curve fitting for the relationship between pu and wheat straw content for different cement content (a) 0 cement content (b)3 cement content (c) 6 cement content (d) 9 cement content

Table 10 a ς and pui in equation (10) obtained by fitting method

Cement content a ς pui Correlation coefficient (R)

0 000861 639527 041324 0998703 000832 689803 055693 0998376 000857 745161 075670 0998659 000848 832193 091686 099934

Table 11 ς and pui in equation (11) obtained by fitting method

Cement content () a ς pui Correlation coefficient (R)

0

00085

651373 041364 0998693 702611 055628 0998356 768670 074533 0959769 858824 092165 099841

12 Advances in Materials Science and Engineering

34 Validity of Derived Equation (16) for Unconfined Com-pressive Strength of Specimens In order to obtain the reli-ability of derived equation (16) for unconfined compressivestrength of specimens the results from derived equation (16)should be compared with those from tests Based onequation (16) unconfined compressive strength of speci-mens mixed with 6 cement content and 02 wheat strawcontent for different curing periods can be obtained asshown in Table 12 In addition test results for unconfinedcompressive strength of specimens mixed with 6 cementcontent and 02 wheat straw content for different curingperiods are also shown in Table 12

As can be seen from Table 12 most of the deviation forunconfined compression strength falls in the range of260sim300 and the maximum deviation for unconfinedcompression strength can reach 316 when curing period is3 days -erefore compared with the test results the ac-curacy of results from the derived equation (16) is not veryhigh also indicating that equation (16) is only applicable tothe approximate evaluation of unconfined compression

strength of saline-alkaline soils In this paper we onlycompare the test result for specimens with combination ofwheat straw content and cement content already used in thecurrent study When using equation (16) to predict theunconfined compression strength of specimens with anothercombination of wheat straw content and cement contentother than what had been already used in the current studyspecimens should be in the state of maximum densitytherefore compaction tests should be firstly carried out toobtain the optimal moisture content of the specimens

4 Conclusions

In this study a series of tests are conducted to study theeffects of wheat straw and cement on the unconfinedcompression strength of specimens -e effect of wheatstraw and cement inclusions and curing periods on un-confined compression strength is determined -e followingconclusions are derived from these tests

-e inclusion of wheat straw within saline-alkaline soilsand saline-alkaline soils mixed with cement causes an in-crease in unconfined compression strength Increasingwheat straw content can increase the peak axial stress andweaken the brittle behavior of saline-alkaline soils mixedwith cement Moreover unconfined compression strengthof specimens increases with increasing curing periods It isknown that the interface roughness for wheat straw plays animportant role in reinforcing the soil Although it is animportant subject no attempt has yet been made to de-termine the optimum degree of the interface roughness Inaddition based on the data obtained from unconfinedcompression strength test a formula for predicting theunconfined compression strength of specimens related tocement content wheat straw content curing periods and soforth is put forward Compared with test results equation(16) is only applicable to the approximate evaluation ofunconfined compression strength of specimens

In addition in the present study we cannot obtain theinfluence of wheat straw content greater than 025 andorcement content greater than 9 on unconfined compressionstrength of specimens of specimens -erefore the appli-cation scope of equation (16) is limited If more test results ofunconfined compression strength of specimens mixed withwheat straw content greater than 025 andor cementcontent greater than 9 are obtained the application ofequation (16) will be more extensive in predicting the un-confined compression strength of specimens with optimalmoisture content Moreover only unconfined compression

00 20 40 60 80 10050

55

60

65

70

75

80

85

90

Cement content ()

ξ

Figure 17 Curve fitting for the relationship between ξ and cementcontent

00 20 40 60 80 100Cement content ()

10

09

08

07

06

05

04

03

02

01

00

p ui (

MPa

)

Figure 18 Curve fitting for the relationship between pui and ce-ment content

Table 12 Unconfined compression strength obtained from testand calculated value by equation (16)

Curingdays

Calculated value(MPa)

Test result(MPa)

Deviation()

3 0179 0136 3167 0398 0312 27614 0581 0449 29428 0582 0461 26256 0681 0529 286

Advances in Materials Science and Engineering 13

strength tests have been conducted on specimensmixed withwheat straw and cement -erefore investigations should becarried out further through other strength tests like directshear tests triaxial shear tests and so forth to study theinfluence of wheat straw on strength of specimens

Data Availability

-e data used to support the findings of this study are in-cluded within the article

Conflicts of Interest

-e authors declare no conflicts of interest with respect tothe research authorship andor publication of this article

Acknowledgments

-is work was financially supported by National NaturalScience Foundation of China (Grant no 51908430) Doc-toral Scientific Fund Project of Weifang University (Grantno 2017BS14) and Science and Technology Project of High-Tech Zone in Weifang (Grant no 2019KJHM09)

References

[1] R L Michalowski and J Cermak ldquoTriaxial compression ofsand reinforced with fibersrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 129 no 2 pp 125ndash1362003

[2] T Yetimoglu M Inanir and O Esatinanir ldquoA study onbearing capacity of randomly distributed fiber-reinforcedsand fills overlying soft clayrdquo Geotextiles and Geomembranesvol 23 no 2 pp 174ndash183 2005

[3] T Park and S Tan ldquoEnhanced performance of reinforced soilwalls by the inclusion of short fiberrdquo Geotextiles and Geo-membranes vol 23 no 4 pp 348ndash361 2005

[4] C Tang B Shi W Gao F Chen and Y Cai ldquoStrength andmechanical behavior of short polypropylene fiber reinforcedand cement stabilized clayey soilrdquo Geotextiles and Geo-membranes vol 25 no 3 pp 194ndash202 2007

[5] S Salah N Shadi and F Fadi ldquoShear strength of fiber-reinforced sandsrdquo Journal of Geotechnical and Geo-environmental Engineering vol 136 no 3 pp 490ndash499 2010

[6] G A Santiago C Franco N C Consoli and V R BotaroldquoStudy of mechanical behavior of a sand soil reinforced withcuraua treated fibers with asphaltrdquo Materials Science Forumvol 730-732 pp 319ndash324 2012

[7] J Prabakar and R S Sridhar ldquoEffect of random inclusion ofsisal fibre on strength behaviour of soilrdquo Construction andBuilding Materials vol 16 no 2 pp 123ndash131 2002

[8] C Mahipal Singh M Satyendra and M BijayanandaldquoPerformance evaluation of silty sand subgrade reinforcedwith fly ash and fibrerdquoGeotextiles and Geomembranes vol 26no 5 pp 429ndash435 2008

[9] M Bouhicha F Aouissi and S Kenai ldquoPerformance ofcomposite soil reinforced with barley strawrdquo Cement andConcrete Composites vol 27 no 5 pp 617ndash621 2005

[10] N C Consoli M D T Casagrande P D M Prietto andA n -ome ldquoPlate load test on fiber-reinforced soilrdquo Journalof Geotechnical and Geoenvironmental Engineering vol 129no 10 pp 951ndash955 2003

[11] J Yao Experimental Study on Strength Characteristics ofWheat Straw Reinforced soil Changrsquoan University XirsquoanChina 2017

[12] A Adili A Rafig S Giovanni et al ldquoStrength of soil rein-forced with fiber materials (papyrus)rdquo Soil Mechanics andFoundation Engineering vol 48 no 6 pp 241ndash247 2012

[13] Y L Qian ldquoExperimentresearch of mechanical properties ofimproved saline soilrdquo Geotechnical Investigation and Sur-veying vol 5 pp 1ndash4 2003

[14] X S Wang H Q Zhang and M Xue ldquoRoad disease andtreatment in saline soil areardquo Journal of Tongji Universityvol 31 no 10 pp 1178ndash1182 2003

[15] Q LWang Y Chao Y F Liu et al ldquoMechanical properties ofsaline soil under the influence of different factorsrdquo FreseniusEnvironmental Bulletin vol 28 no 2A pp 1366ndash1373 2019

[16] L Wei S X Chai H Z Cai et al ldquoResearch on tensility ofwheat straw for reinforced materialrdquo Rock amp Soil Mechanicsvol 31 no 1 pp 128ndash132 2010

[17] L Wei S X Chai H Z Cai et al ldquoPhysical and mechanicalproperties of wheat straw and unconfined compressivestrength of reinforced inshore saline soil with wheat strawrdquoChina Civil Engineering Journal vol 43 no 3 pp 93ndash982010

[18] M Li S X Chai H P Du et al ldquoReasonable reinforcementposition and shear strength model of reinforced saline soilwith wheat straw and limerdquo Chinese Jourhal of Rock Me-chanics and Engineering vol 29 no sup 2 pp 3923ndash39292010

[19] P Wang S X Chai X Y Wang et al ldquoAnalysis of effectfactors of heavy compaction test for wheat straw-reinforcedsaline soilrdquo Rock and Soil Mechanics vol 32 no 2pp 448ndash452 2011

[20] L Wei S X Chai H Z Cai et al ldquoTriaxial shear strength anddeviatoric stress-strain of saline soils reinforced with wheatstrawsrdquo China Civil Engineering Journal vol 45 no 1pp 109ndash114 2012

[21] H Lu C G Yan X H Yang et al ldquoExperiment on anti-eroding property of reinforced loess with wheat strawrdquoJournal of Changrsquoan University (Natural Science Edition)vol 37 no 1 pp 24ndash32 2017

[22] J B Hao X MWei J Yao et al ldquoStrength characteristics andmesostructure of wheat straw einforced soilrdquo Journal of TongjiUniversity (Natural Science) vol 47 no 6 pp 764ndash831 2019

[23] GB50007-2011 Code for Design of Building foundationMinistry of Housing and Urban-Rural Development BeijingChina 2012

[24] JTG D30-2015 Specifications for Design of Highway Sub-grades China Communications Publishing amp Media Man-agement Co Ltd Beijing China 2016

[25] GBT 50123-1999 Standard for Soil Test Method Ministry ofConstruction Beijing China 2000

14 Advances in Materials Science and Engineering

mixed with 02 wheat straw content and different cementcontent is shown in Figures 13(a)ndash13(d)

In Figures 13(a)ndash13(d) the curve fitting can be expressedby the following expression

p pu minus p0( 1113857 middot 1 minus e(minus αmiddott)

1113872 1113873 + p0 (3)

where p is unconfined compressive strength of specimens tis curing period pu is ultimate unconfined compressivestrength p0 is initial unconfined compressive strength α isthe coefficient related to the shape of curves

In equation (3) using fitting method pu p0 and α canbe obtained based on the data from Figures 12(a)ndash12(d) asshown in Table 5

As shown in Table 5 α is in the range of 014398 to014643 showing that the change of the value of α is verylittle -e mean value for α is 014533 -erefore in order tosimplify equation (1) the value of α is replaced by 0145 andequation (1) can be expressed as

p pu minus p0( 1113857 middot 1 minus e(minus 0145middott)

1113872 1113873 + p0 (4)

331 Initial Unconfined Compressive Strength p0 Inequation (4) p0 and pu can also be obtained based on the datafrom Figures 10(a)ndash10(d) by fitting method as shown inTable 6 Based on the data fromTable 6 the curve fitting for therelationship between p0 and wheat straw content for differentcement content can be obtained as shown in Figure 14

For the curve fitting in Figures 14(a)ndash14(d) it can bedescribed by the following expression

p0 η middot ebmiddotas + p0i (5)

where η is the coefficient for curve growth as is wheatstraw content b is the exponent p0i is initial uncon-fined compressive strength only related to cement con-tent Based on the data from Table 6 η b and p0i inequation (5) can be obtained by fitting method as shownin Table 7

As can be seen from Table 7 the change of η is very littleand the mean value for η is 00017 -erefore equation (5)can be simplified and expressed as

p0 00017 middot ebmiddotas + p0i (6)

Similarly based on the data from Table 6 and equation(6) b and p0i can be obtained by fitting method as shown inTable 8

As shown in Table 8 the change of b is also very little andthe mean value for b is 9356 -erefore in order to simplifyequation (6) b is replaced by 9356 in equation (6) and thenit is expressed as

p0 00017 middot e9356middotas + p0i (7)

Moreover as can be seen from Table 8 p0i is related tocement content Based on the data from Table 8 the rela-tionship between p0i and cement content can also be ob-tained as shown in Figure 15

(a) (b) (c) (d) (e)

Figure 10 Effect of wheat straw content on failure mechanism of specimens mixed with 6 cement content (a) 0 wheat straw content (b)010 wheat straw content (c) 015 wheat straw content (d) 020 wheat straw content (e) 025 wheat straw content

(a) (b) (c) (d) (e)

Figure 11 Effect of curing period on failure mechanism of specimens mixed with 3 cement content and 01 wheat straw content (a) 3days (b) 7 days (c) 14 days (d) 28 days (e) 56 days

Advances in Materials Science and Engineering 7

-e curve fitting for relationship between p0i and cementcontent in Figure 15 can be expressed as

p0i 008014 + 001086 middot ac (8)

where ac is cement content -erefore equation (7) canbe expressed as

p0 00017 middot e9356middotas + 001086 middot ac + 008014 (9)

332 Ultimate Unconfined Compressive Strength pu In thissection equation (4) is also used to determine the value of puHowever in equation (4)p0 can be obtained from equation (9)

according to the cement content and wheat straw contentFurthermore based on the data from Figures 12(a)ndash12(d) pucan be obtained with equation (3) as shown in Table 9

For the curve fitting in Figure 16 it can be described bythe following expression

pu a middot eminus ςmiddotas( ) + pui (10)

where a is the coefficient related to curve growth as is wheatstraw content b is the exponent pui is initial ultimateunconfined compressive strength of specimens only relatedto cement content Similarly a ς and pui in equation (10)can be obtained by fitting method based on the data fromTable 9 as shown in Table 10

0 10 20 30 40 50 60 7000

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing age (day)

0 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(a)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing age (day)

3 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(b)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing age (day)

6 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(c)

00

01

02

03

04

05

06

07Pe

ak st

ress

σ (M

Pa)

0 10 20 30 40 50 60 70Curing age (day)

9 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(d)

Figure 12 Effect of curing periods on unconfined compressive strength of specimens mixed with wheat straws and different cementcontent (a) 0 cement content (b) 3 cement content (c) 6 cement content (d) 9 cement content

8 Advances in Materials Science and Engineering

0 10 20 30 40 50 60 7000

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing aging (day)

0 cement content

(a)

000 10 20 30 40 50 60 70

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing aging (day)

3 cement content

(b)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing aging (day)

6 cement content

(c)

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing aging (day)

9 cement content

(d)

Figure 13 Curve fitting for the relationship between curing periods and unconfined compressive strength of specimens mixed with 02wheat straw and different cement content (a) 0 cement content (b) 3 cement content (c) 6 cement content (d) 9 cement content

Table 5 pu p0 and α in equation (3) obtained by fitting method

Cement content () Wheat straw content () A pu p0 Correlation coefficient (R)

0

000 014588 043154 009152 098592010 014516 044304 009313 098594015 014618 044932 009624 098513020 014544 045447 010006 098573025 014475 046229 010691 098532

3

000 014579 058251 012124 098826010 014551 058510 012383 098837015 014540 058738 012611 098756020 014464 059306 013179 098620025 014476 059871 013744 098922

6

000 014398 073439 015303 098871010 014613 073703 015567 098887015 014558 074029 015893 098998020 014623 074398 016262 098928025 014489 074994 016858 099096

9

000 014483 089900 018327 099765010 014643 090140 018567 099796015 014568 090410 018837 099796020 014456 090841 019268 099864025 014483 091405 019832 099801

Advances in Materials Science and Engineering 9

Table 6 p0 and pu in equation (4) obtained by fitting method

Cement content () Wheat straw content () α pu p0 Correlation coefficient (R)

0

000

0145

042040 008205 098389010 043203 008498 098396015 043892 008708 098338020 044639 009132 098464025 045536 009759 098451

3

000

0145

056306 011459 098765010 057668 011623 098763015 058741 011906 098752020 059589 012309 098607025 061033 012917 098894

6

000

0145

075501 014632 098870010 075883 014825 098885015 076059 015161 098966020 076642 015566 098839025 078146 016166 099062

9

000

0145

093233 018034 099679010 094507 018203 099703015 095207 018589 099711020 095780 018931 099748025 096357 019594 099705

000

002

004

006

008

010

012

014

016

018

020

022

024

026

0080

0085

0090

0095

0100

P 0 (M

Pa)

Wheat straw content as ()

0 cement content

(a)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0110

0115

0120

0125

0130

3 cement content

(b)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0140

0145

0150

0155

0160

0165

0170

6 cement content

(c)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0175

0180

0185

0190

0195

0200

9 cement content

(d)

Figure 14 Curve fitting for the relationship between p0 and wheat straw content for different cement content (a) 0 cement content (b)3 cement content (c) 6 cement content (d) 9 cement content

10 Advances in Materials Science and Engineering

As can be seen from Table 10 a is in the range of 000832to 000861 showing that the change of a is very little -emean value for a is 000849 and the value of a in equation(10) is replaced by 00085 then equation (10) can beexpressed as

pu 00085 middot eminus ξmiddotas( ) + pui (11)

-en based on equation (11) and the data in Table 9 ςand pui can be further obtained by fitting method as shownin Table 11

Figure 17 shows the curve fitting for the relationshipbetween ξ and cement content and the following expressioncan describe the curve fitting

ξ a1 middot eminus b1 middotac( ) + ξ0 (12)

where a1 is the coefficient related to curve growth ac iscement content b1 is the exponent ξ0 is initial value of ξonly related to cement content Based on the data fromTable 11 a1 b1 and ξ0 can be obtained by fitting methodwhich are 1514 0096 and 5002 respectively -ereforeequation (12) can be expressed as

ξ 1514 middot eminus 0096middotac( ) + 5002 (13)

Moreover Figure 18 shows the curve fitting for therelationship between pui and cement content -e followingexpression can describe the fitting curve in Figure 18

pui 00571 middot ac + 040226 (14)

-erefore substituting equations (13) and (14) intoequation (11) it can be expressed as

pu 00085 middot eminus 1514middote minus0096middotac( )+5002( 1113857middotas( 1113857

+ 00571 middot ac + 040226

(15)

p0 and pu in equation (4) are replaced by equations (9) and(15) then equation (4) can be expressed as

p 00085 middot e minus 1514middote minus0096middotac( )+5002( 1113857middotas( + 004624 middot ac + 004624

minus00017 middot e9356middotas

⎛⎝ ⎞⎠

middot 1 minus e(minus 0145middott)

1113872 1113873 + 000165 middot e9356middotas + 001086 middot ac + 008014

(16)

From the published literature [16] ultimate unconfinedcompressive strength increased firstly with adding wheatstraws however with further increasing of wheat strawscontent the ultimate unconfined compressive strength de-creased In test we cannot find the maximum wheat strawscontent and therefore when using equation (16) to predictthe ultimate unconfined compressive strength wheat straws

Table 7 η b and p0i in equation (5) obtained by fitting method

Cement content () Η b p0i Correlation coefficient (R)

0 000176 892416 008035 0999653 000159 910512 011308 0998956 000188 938257 014420 0998449 000167 1008636 017843 099709

Table 8 b and p0i in equation (6) obtained by fitting method

Cement content b p0i Correlation coefficient (R)

0 934882 008053 0999623 924118 011252 0998586 939121 014456 0998329 944322 017848 099709

00 20 40 60 80 100

008

010

012

014

016

018

020

P 0i (

MPa

)

Cement content ()

Figure 15 Curve fitting for the relationship between p0i andcement content

Table 9 pu in equation (3) obtained with equation (4)

Cement content () Wheat straw content() α pu

0

000

0145

042179010 043434015 043685020 044085025 045725

3

000

0145

056437010 057692015 058943020 059343025 061983

6

000

0145

075695010 075950015 076201020 076601025 078241

9

000

0145

092953010 094208015 095459020 095859025 096499

Advances in Materials Science and Engineering 11

content cannot exceed 025 by weight of saline-alkalinesoils In addition when cement content in specimens isgreater than 9 by weight of saline-alkaline soils we cannotperform a series of tests to obtain the influence of cementcontent on ultimate unconfined compressive strength andtherefore in the application of equation (16) cement content

should be less than 9 Moreover for equation (16) derivedfrom the test on specimens with optimum water contentwhen using it to predict the ultimate unconfined com-pressive strength for specimens the range of optimum watercontent for specimens should fall into 127sim145 byweight of saline-alkaline soils

0 cement content

041504200425043004350440044504500455

04650460

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(a)

3 cement content

030010 015 020 025005000Wheat straw content ()

056005650570057505800585059005950600060506100615062006250630

P u (M

Pa)

(b)

0750

0755

0760

0765

0770

0775

0780

0785

0790

6 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(c)

09200925093009350940094509500955096009650970

9 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(d)

Figure 16 Curve fitting for the relationship between pu and wheat straw content for different cement content (a) 0 cement content (b)3 cement content (c) 6 cement content (d) 9 cement content

Table 10 a ς and pui in equation (10) obtained by fitting method

Cement content a ς pui Correlation coefficient (R)

0 000861 639527 041324 0998703 000832 689803 055693 0998376 000857 745161 075670 0998659 000848 832193 091686 099934

Table 11 ς and pui in equation (11) obtained by fitting method

Cement content () a ς pui Correlation coefficient (R)

0

00085

651373 041364 0998693 702611 055628 0998356 768670 074533 0959769 858824 092165 099841

12 Advances in Materials Science and Engineering

34 Validity of Derived Equation (16) for Unconfined Com-pressive Strength of Specimens In order to obtain the reli-ability of derived equation (16) for unconfined compressivestrength of specimens the results from derived equation (16)should be compared with those from tests Based onequation (16) unconfined compressive strength of speci-mens mixed with 6 cement content and 02 wheat strawcontent for different curing periods can be obtained asshown in Table 12 In addition test results for unconfinedcompressive strength of specimens mixed with 6 cementcontent and 02 wheat straw content for different curingperiods are also shown in Table 12

As can be seen from Table 12 most of the deviation forunconfined compression strength falls in the range of260sim300 and the maximum deviation for unconfinedcompression strength can reach 316 when curing period is3 days -erefore compared with the test results the ac-curacy of results from the derived equation (16) is not veryhigh also indicating that equation (16) is only applicable tothe approximate evaluation of unconfined compression

strength of saline-alkaline soils In this paper we onlycompare the test result for specimens with combination ofwheat straw content and cement content already used in thecurrent study When using equation (16) to predict theunconfined compression strength of specimens with anothercombination of wheat straw content and cement contentother than what had been already used in the current studyspecimens should be in the state of maximum densitytherefore compaction tests should be firstly carried out toobtain the optimal moisture content of the specimens

4 Conclusions

In this study a series of tests are conducted to study theeffects of wheat straw and cement on the unconfinedcompression strength of specimens -e effect of wheatstraw and cement inclusions and curing periods on un-confined compression strength is determined -e followingconclusions are derived from these tests

-e inclusion of wheat straw within saline-alkaline soilsand saline-alkaline soils mixed with cement causes an in-crease in unconfined compression strength Increasingwheat straw content can increase the peak axial stress andweaken the brittle behavior of saline-alkaline soils mixedwith cement Moreover unconfined compression strengthof specimens increases with increasing curing periods It isknown that the interface roughness for wheat straw plays animportant role in reinforcing the soil Although it is animportant subject no attempt has yet been made to de-termine the optimum degree of the interface roughness Inaddition based on the data obtained from unconfinedcompression strength test a formula for predicting theunconfined compression strength of specimens related tocement content wheat straw content curing periods and soforth is put forward Compared with test results equation(16) is only applicable to the approximate evaluation ofunconfined compression strength of specimens

In addition in the present study we cannot obtain theinfluence of wheat straw content greater than 025 andorcement content greater than 9 on unconfined compressionstrength of specimens of specimens -erefore the appli-cation scope of equation (16) is limited If more test results ofunconfined compression strength of specimens mixed withwheat straw content greater than 025 andor cementcontent greater than 9 are obtained the application ofequation (16) will be more extensive in predicting the un-confined compression strength of specimens with optimalmoisture content Moreover only unconfined compression

00 20 40 60 80 10050

55

60

65

70

75

80

85

90

Cement content ()

ξ

Figure 17 Curve fitting for the relationship between ξ and cementcontent

00 20 40 60 80 100Cement content ()

10

09

08

07

06

05

04

03

02

01

00

p ui (

MPa

)

Figure 18 Curve fitting for the relationship between pui and ce-ment content

Table 12 Unconfined compression strength obtained from testand calculated value by equation (16)

Curingdays

Calculated value(MPa)

Test result(MPa)

Deviation()

3 0179 0136 3167 0398 0312 27614 0581 0449 29428 0582 0461 26256 0681 0529 286

Advances in Materials Science and Engineering 13

strength tests have been conducted on specimensmixed withwheat straw and cement -erefore investigations should becarried out further through other strength tests like directshear tests triaxial shear tests and so forth to study theinfluence of wheat straw on strength of specimens

Data Availability

-e data used to support the findings of this study are in-cluded within the article

Conflicts of Interest

-e authors declare no conflicts of interest with respect tothe research authorship andor publication of this article

Acknowledgments

-is work was financially supported by National NaturalScience Foundation of China (Grant no 51908430) Doc-toral Scientific Fund Project of Weifang University (Grantno 2017BS14) and Science and Technology Project of High-Tech Zone in Weifang (Grant no 2019KJHM09)

References

[1] R L Michalowski and J Cermak ldquoTriaxial compression ofsand reinforced with fibersrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 129 no 2 pp 125ndash1362003

[2] T Yetimoglu M Inanir and O Esatinanir ldquoA study onbearing capacity of randomly distributed fiber-reinforcedsand fills overlying soft clayrdquo Geotextiles and Geomembranesvol 23 no 2 pp 174ndash183 2005

[3] T Park and S Tan ldquoEnhanced performance of reinforced soilwalls by the inclusion of short fiberrdquo Geotextiles and Geo-membranes vol 23 no 4 pp 348ndash361 2005

[4] C Tang B Shi W Gao F Chen and Y Cai ldquoStrength andmechanical behavior of short polypropylene fiber reinforcedand cement stabilized clayey soilrdquo Geotextiles and Geo-membranes vol 25 no 3 pp 194ndash202 2007

[5] S Salah N Shadi and F Fadi ldquoShear strength of fiber-reinforced sandsrdquo Journal of Geotechnical and Geo-environmental Engineering vol 136 no 3 pp 490ndash499 2010

[6] G A Santiago C Franco N C Consoli and V R BotaroldquoStudy of mechanical behavior of a sand soil reinforced withcuraua treated fibers with asphaltrdquo Materials Science Forumvol 730-732 pp 319ndash324 2012

[7] J Prabakar and R S Sridhar ldquoEffect of random inclusion ofsisal fibre on strength behaviour of soilrdquo Construction andBuilding Materials vol 16 no 2 pp 123ndash131 2002

[8] C Mahipal Singh M Satyendra and M BijayanandaldquoPerformance evaluation of silty sand subgrade reinforcedwith fly ash and fibrerdquoGeotextiles and Geomembranes vol 26no 5 pp 429ndash435 2008

[9] M Bouhicha F Aouissi and S Kenai ldquoPerformance ofcomposite soil reinforced with barley strawrdquo Cement andConcrete Composites vol 27 no 5 pp 617ndash621 2005

[10] N C Consoli M D T Casagrande P D M Prietto andA n -ome ldquoPlate load test on fiber-reinforced soilrdquo Journalof Geotechnical and Geoenvironmental Engineering vol 129no 10 pp 951ndash955 2003

[11] J Yao Experimental Study on Strength Characteristics ofWheat Straw Reinforced soil Changrsquoan University XirsquoanChina 2017

[12] A Adili A Rafig S Giovanni et al ldquoStrength of soil rein-forced with fiber materials (papyrus)rdquo Soil Mechanics andFoundation Engineering vol 48 no 6 pp 241ndash247 2012

[13] Y L Qian ldquoExperimentresearch of mechanical properties ofimproved saline soilrdquo Geotechnical Investigation and Sur-veying vol 5 pp 1ndash4 2003

[14] X S Wang H Q Zhang and M Xue ldquoRoad disease andtreatment in saline soil areardquo Journal of Tongji Universityvol 31 no 10 pp 1178ndash1182 2003

[15] Q LWang Y Chao Y F Liu et al ldquoMechanical properties ofsaline soil under the influence of different factorsrdquo FreseniusEnvironmental Bulletin vol 28 no 2A pp 1366ndash1373 2019

[16] L Wei S X Chai H Z Cai et al ldquoResearch on tensility ofwheat straw for reinforced materialrdquo Rock amp Soil Mechanicsvol 31 no 1 pp 128ndash132 2010

[17] L Wei S X Chai H Z Cai et al ldquoPhysical and mechanicalproperties of wheat straw and unconfined compressivestrength of reinforced inshore saline soil with wheat strawrdquoChina Civil Engineering Journal vol 43 no 3 pp 93ndash982010

[18] M Li S X Chai H P Du et al ldquoReasonable reinforcementposition and shear strength model of reinforced saline soilwith wheat straw and limerdquo Chinese Jourhal of Rock Me-chanics and Engineering vol 29 no sup 2 pp 3923ndash39292010

[19] P Wang S X Chai X Y Wang et al ldquoAnalysis of effectfactors of heavy compaction test for wheat straw-reinforcedsaline soilrdquo Rock and Soil Mechanics vol 32 no 2pp 448ndash452 2011

[20] L Wei S X Chai H Z Cai et al ldquoTriaxial shear strength anddeviatoric stress-strain of saline soils reinforced with wheatstrawsrdquo China Civil Engineering Journal vol 45 no 1pp 109ndash114 2012

[21] H Lu C G Yan X H Yang et al ldquoExperiment on anti-eroding property of reinforced loess with wheat strawrdquoJournal of Changrsquoan University (Natural Science Edition)vol 37 no 1 pp 24ndash32 2017

[22] J B Hao X MWei J Yao et al ldquoStrength characteristics andmesostructure of wheat straw einforced soilrdquo Journal of TongjiUniversity (Natural Science) vol 47 no 6 pp 764ndash831 2019

[23] GB50007-2011 Code for Design of Building foundationMinistry of Housing and Urban-Rural Development BeijingChina 2012

[24] JTG D30-2015 Specifications for Design of Highway Sub-grades China Communications Publishing amp Media Man-agement Co Ltd Beijing China 2016

[25] GBT 50123-1999 Standard for Soil Test Method Ministry ofConstruction Beijing China 2000

14 Advances in Materials Science and Engineering

-e curve fitting for relationship between p0i and cementcontent in Figure 15 can be expressed as

p0i 008014 + 001086 middot ac (8)

where ac is cement content -erefore equation (7) canbe expressed as

p0 00017 middot e9356middotas + 001086 middot ac + 008014 (9)

332 Ultimate Unconfined Compressive Strength pu In thissection equation (4) is also used to determine the value of puHowever in equation (4)p0 can be obtained from equation (9)

according to the cement content and wheat straw contentFurthermore based on the data from Figures 12(a)ndash12(d) pucan be obtained with equation (3) as shown in Table 9

For the curve fitting in Figure 16 it can be described bythe following expression

pu a middot eminus ςmiddotas( ) + pui (10)

where a is the coefficient related to curve growth as is wheatstraw content b is the exponent pui is initial ultimateunconfined compressive strength of specimens only relatedto cement content Similarly a ς and pui in equation (10)can be obtained by fitting method based on the data fromTable 9 as shown in Table 10

0 10 20 30 40 50 60 7000

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing age (day)

0 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(a)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing age (day)

3 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(b)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing age (day)

6 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(c)

00

01

02

03

04

05

06

07Pe

ak st

ress

σ (M

Pa)

0 10 20 30 40 50 60 70Curing age (day)

9 cement content

000 wheat straw content010 wheat straw content015 wheat straw content020 wheat straw content025 wheat straw content

(d)

Figure 12 Effect of curing periods on unconfined compressive strength of specimens mixed with wheat straws and different cementcontent (a) 0 cement content (b) 3 cement content (c) 6 cement content (d) 9 cement content

8 Advances in Materials Science and Engineering

0 10 20 30 40 50 60 7000

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing aging (day)

0 cement content

(a)

000 10 20 30 40 50 60 70

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing aging (day)

3 cement content

(b)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing aging (day)

6 cement content

(c)

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing aging (day)

9 cement content

(d)

Figure 13 Curve fitting for the relationship between curing periods and unconfined compressive strength of specimens mixed with 02wheat straw and different cement content (a) 0 cement content (b) 3 cement content (c) 6 cement content (d) 9 cement content

Table 5 pu p0 and α in equation (3) obtained by fitting method

Cement content () Wheat straw content () A pu p0 Correlation coefficient (R)

0

000 014588 043154 009152 098592010 014516 044304 009313 098594015 014618 044932 009624 098513020 014544 045447 010006 098573025 014475 046229 010691 098532

3

000 014579 058251 012124 098826010 014551 058510 012383 098837015 014540 058738 012611 098756020 014464 059306 013179 098620025 014476 059871 013744 098922

6

000 014398 073439 015303 098871010 014613 073703 015567 098887015 014558 074029 015893 098998020 014623 074398 016262 098928025 014489 074994 016858 099096

9

000 014483 089900 018327 099765010 014643 090140 018567 099796015 014568 090410 018837 099796020 014456 090841 019268 099864025 014483 091405 019832 099801

Advances in Materials Science and Engineering 9

Table 6 p0 and pu in equation (4) obtained by fitting method

Cement content () Wheat straw content () α pu p0 Correlation coefficient (R)

0

000

0145

042040 008205 098389010 043203 008498 098396015 043892 008708 098338020 044639 009132 098464025 045536 009759 098451

3

000

0145

056306 011459 098765010 057668 011623 098763015 058741 011906 098752020 059589 012309 098607025 061033 012917 098894

6

000

0145

075501 014632 098870010 075883 014825 098885015 076059 015161 098966020 076642 015566 098839025 078146 016166 099062

9

000

0145

093233 018034 099679010 094507 018203 099703015 095207 018589 099711020 095780 018931 099748025 096357 019594 099705

000

002

004

006

008

010

012

014

016

018

020

022

024

026

0080

0085

0090

0095

0100

P 0 (M

Pa)

Wheat straw content as ()

0 cement content

(a)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0110

0115

0120

0125

0130

3 cement content

(b)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0140

0145

0150

0155

0160

0165

0170

6 cement content

(c)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0175

0180

0185

0190

0195

0200

9 cement content

(d)

Figure 14 Curve fitting for the relationship between p0 and wheat straw content for different cement content (a) 0 cement content (b)3 cement content (c) 6 cement content (d) 9 cement content

10 Advances in Materials Science and Engineering

As can be seen from Table 10 a is in the range of 000832to 000861 showing that the change of a is very little -emean value for a is 000849 and the value of a in equation(10) is replaced by 00085 then equation (10) can beexpressed as

pu 00085 middot eminus ξmiddotas( ) + pui (11)

-en based on equation (11) and the data in Table 9 ςand pui can be further obtained by fitting method as shownin Table 11

Figure 17 shows the curve fitting for the relationshipbetween ξ and cement content and the following expressioncan describe the curve fitting

ξ a1 middot eminus b1 middotac( ) + ξ0 (12)

where a1 is the coefficient related to curve growth ac iscement content b1 is the exponent ξ0 is initial value of ξonly related to cement content Based on the data fromTable 11 a1 b1 and ξ0 can be obtained by fitting methodwhich are 1514 0096 and 5002 respectively -ereforeequation (12) can be expressed as

ξ 1514 middot eminus 0096middotac( ) + 5002 (13)

Moreover Figure 18 shows the curve fitting for therelationship between pui and cement content -e followingexpression can describe the fitting curve in Figure 18

pui 00571 middot ac + 040226 (14)

-erefore substituting equations (13) and (14) intoequation (11) it can be expressed as

pu 00085 middot eminus 1514middote minus0096middotac( )+5002( 1113857middotas( 1113857

+ 00571 middot ac + 040226

(15)

p0 and pu in equation (4) are replaced by equations (9) and(15) then equation (4) can be expressed as

p 00085 middot e minus 1514middote minus0096middotac( )+5002( 1113857middotas( + 004624 middot ac + 004624

minus00017 middot e9356middotas

⎛⎝ ⎞⎠

middot 1 minus e(minus 0145middott)

1113872 1113873 + 000165 middot e9356middotas + 001086 middot ac + 008014

(16)

From the published literature [16] ultimate unconfinedcompressive strength increased firstly with adding wheatstraws however with further increasing of wheat strawscontent the ultimate unconfined compressive strength de-creased In test we cannot find the maximum wheat strawscontent and therefore when using equation (16) to predictthe ultimate unconfined compressive strength wheat straws

Table 7 η b and p0i in equation (5) obtained by fitting method

Cement content () Η b p0i Correlation coefficient (R)

0 000176 892416 008035 0999653 000159 910512 011308 0998956 000188 938257 014420 0998449 000167 1008636 017843 099709

Table 8 b and p0i in equation (6) obtained by fitting method

Cement content b p0i Correlation coefficient (R)

0 934882 008053 0999623 924118 011252 0998586 939121 014456 0998329 944322 017848 099709

00 20 40 60 80 100

008

010

012

014

016

018

020

P 0i (

MPa

)

Cement content ()

Figure 15 Curve fitting for the relationship between p0i andcement content

Table 9 pu in equation (3) obtained with equation (4)

Cement content () Wheat straw content() α pu

0

000

0145

042179010 043434015 043685020 044085025 045725

3

000

0145

056437010 057692015 058943020 059343025 061983

6

000

0145

075695010 075950015 076201020 076601025 078241

9

000

0145

092953010 094208015 095459020 095859025 096499

Advances in Materials Science and Engineering 11

content cannot exceed 025 by weight of saline-alkalinesoils In addition when cement content in specimens isgreater than 9 by weight of saline-alkaline soils we cannotperform a series of tests to obtain the influence of cementcontent on ultimate unconfined compressive strength andtherefore in the application of equation (16) cement content

should be less than 9 Moreover for equation (16) derivedfrom the test on specimens with optimum water contentwhen using it to predict the ultimate unconfined com-pressive strength for specimens the range of optimum watercontent for specimens should fall into 127sim145 byweight of saline-alkaline soils

0 cement content

041504200425043004350440044504500455

04650460

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(a)

3 cement content

030010 015 020 025005000Wheat straw content ()

056005650570057505800585059005950600060506100615062006250630

P u (M

Pa)

(b)

0750

0755

0760

0765

0770

0775

0780

0785

0790

6 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(c)

09200925093009350940094509500955096009650970

9 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(d)

Figure 16 Curve fitting for the relationship between pu and wheat straw content for different cement content (a) 0 cement content (b)3 cement content (c) 6 cement content (d) 9 cement content

Table 10 a ς and pui in equation (10) obtained by fitting method

Cement content a ς pui Correlation coefficient (R)

0 000861 639527 041324 0998703 000832 689803 055693 0998376 000857 745161 075670 0998659 000848 832193 091686 099934

Table 11 ς and pui in equation (11) obtained by fitting method

Cement content () a ς pui Correlation coefficient (R)

0

00085

651373 041364 0998693 702611 055628 0998356 768670 074533 0959769 858824 092165 099841

12 Advances in Materials Science and Engineering

34 Validity of Derived Equation (16) for Unconfined Com-pressive Strength of Specimens In order to obtain the reli-ability of derived equation (16) for unconfined compressivestrength of specimens the results from derived equation (16)should be compared with those from tests Based onequation (16) unconfined compressive strength of speci-mens mixed with 6 cement content and 02 wheat strawcontent for different curing periods can be obtained asshown in Table 12 In addition test results for unconfinedcompressive strength of specimens mixed with 6 cementcontent and 02 wheat straw content for different curingperiods are also shown in Table 12

As can be seen from Table 12 most of the deviation forunconfined compression strength falls in the range of260sim300 and the maximum deviation for unconfinedcompression strength can reach 316 when curing period is3 days -erefore compared with the test results the ac-curacy of results from the derived equation (16) is not veryhigh also indicating that equation (16) is only applicable tothe approximate evaluation of unconfined compression

strength of saline-alkaline soils In this paper we onlycompare the test result for specimens with combination ofwheat straw content and cement content already used in thecurrent study When using equation (16) to predict theunconfined compression strength of specimens with anothercombination of wheat straw content and cement contentother than what had been already used in the current studyspecimens should be in the state of maximum densitytherefore compaction tests should be firstly carried out toobtain the optimal moisture content of the specimens

4 Conclusions

In this study a series of tests are conducted to study theeffects of wheat straw and cement on the unconfinedcompression strength of specimens -e effect of wheatstraw and cement inclusions and curing periods on un-confined compression strength is determined -e followingconclusions are derived from these tests

-e inclusion of wheat straw within saline-alkaline soilsand saline-alkaline soils mixed with cement causes an in-crease in unconfined compression strength Increasingwheat straw content can increase the peak axial stress andweaken the brittle behavior of saline-alkaline soils mixedwith cement Moreover unconfined compression strengthof specimens increases with increasing curing periods It isknown that the interface roughness for wheat straw plays animportant role in reinforcing the soil Although it is animportant subject no attempt has yet been made to de-termine the optimum degree of the interface roughness Inaddition based on the data obtained from unconfinedcompression strength test a formula for predicting theunconfined compression strength of specimens related tocement content wheat straw content curing periods and soforth is put forward Compared with test results equation(16) is only applicable to the approximate evaluation ofunconfined compression strength of specimens

In addition in the present study we cannot obtain theinfluence of wheat straw content greater than 025 andorcement content greater than 9 on unconfined compressionstrength of specimens of specimens -erefore the appli-cation scope of equation (16) is limited If more test results ofunconfined compression strength of specimens mixed withwheat straw content greater than 025 andor cementcontent greater than 9 are obtained the application ofequation (16) will be more extensive in predicting the un-confined compression strength of specimens with optimalmoisture content Moreover only unconfined compression

00 20 40 60 80 10050

55

60

65

70

75

80

85

90

Cement content ()

ξ

Figure 17 Curve fitting for the relationship between ξ and cementcontent

00 20 40 60 80 100Cement content ()

10

09

08

07

06

05

04

03

02

01

00

p ui (

MPa

)

Figure 18 Curve fitting for the relationship between pui and ce-ment content

Table 12 Unconfined compression strength obtained from testand calculated value by equation (16)

Curingdays

Calculated value(MPa)

Test result(MPa)

Deviation()

3 0179 0136 3167 0398 0312 27614 0581 0449 29428 0582 0461 26256 0681 0529 286

Advances in Materials Science and Engineering 13

strength tests have been conducted on specimensmixed withwheat straw and cement -erefore investigations should becarried out further through other strength tests like directshear tests triaxial shear tests and so forth to study theinfluence of wheat straw on strength of specimens

Data Availability

-e data used to support the findings of this study are in-cluded within the article

Conflicts of Interest

-e authors declare no conflicts of interest with respect tothe research authorship andor publication of this article

Acknowledgments

-is work was financially supported by National NaturalScience Foundation of China (Grant no 51908430) Doc-toral Scientific Fund Project of Weifang University (Grantno 2017BS14) and Science and Technology Project of High-Tech Zone in Weifang (Grant no 2019KJHM09)

References

[1] R L Michalowski and J Cermak ldquoTriaxial compression ofsand reinforced with fibersrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 129 no 2 pp 125ndash1362003

[2] T Yetimoglu M Inanir and O Esatinanir ldquoA study onbearing capacity of randomly distributed fiber-reinforcedsand fills overlying soft clayrdquo Geotextiles and Geomembranesvol 23 no 2 pp 174ndash183 2005

[3] T Park and S Tan ldquoEnhanced performance of reinforced soilwalls by the inclusion of short fiberrdquo Geotextiles and Geo-membranes vol 23 no 4 pp 348ndash361 2005

[4] C Tang B Shi W Gao F Chen and Y Cai ldquoStrength andmechanical behavior of short polypropylene fiber reinforcedand cement stabilized clayey soilrdquo Geotextiles and Geo-membranes vol 25 no 3 pp 194ndash202 2007

[5] S Salah N Shadi and F Fadi ldquoShear strength of fiber-reinforced sandsrdquo Journal of Geotechnical and Geo-environmental Engineering vol 136 no 3 pp 490ndash499 2010

[6] G A Santiago C Franco N C Consoli and V R BotaroldquoStudy of mechanical behavior of a sand soil reinforced withcuraua treated fibers with asphaltrdquo Materials Science Forumvol 730-732 pp 319ndash324 2012

[7] J Prabakar and R S Sridhar ldquoEffect of random inclusion ofsisal fibre on strength behaviour of soilrdquo Construction andBuilding Materials vol 16 no 2 pp 123ndash131 2002

[8] C Mahipal Singh M Satyendra and M BijayanandaldquoPerformance evaluation of silty sand subgrade reinforcedwith fly ash and fibrerdquoGeotextiles and Geomembranes vol 26no 5 pp 429ndash435 2008

[9] M Bouhicha F Aouissi and S Kenai ldquoPerformance ofcomposite soil reinforced with barley strawrdquo Cement andConcrete Composites vol 27 no 5 pp 617ndash621 2005

[10] N C Consoli M D T Casagrande P D M Prietto andA n -ome ldquoPlate load test on fiber-reinforced soilrdquo Journalof Geotechnical and Geoenvironmental Engineering vol 129no 10 pp 951ndash955 2003

[11] J Yao Experimental Study on Strength Characteristics ofWheat Straw Reinforced soil Changrsquoan University XirsquoanChina 2017

[12] A Adili A Rafig S Giovanni et al ldquoStrength of soil rein-forced with fiber materials (papyrus)rdquo Soil Mechanics andFoundation Engineering vol 48 no 6 pp 241ndash247 2012

[13] Y L Qian ldquoExperimentresearch of mechanical properties ofimproved saline soilrdquo Geotechnical Investigation and Sur-veying vol 5 pp 1ndash4 2003

[14] X S Wang H Q Zhang and M Xue ldquoRoad disease andtreatment in saline soil areardquo Journal of Tongji Universityvol 31 no 10 pp 1178ndash1182 2003

[15] Q LWang Y Chao Y F Liu et al ldquoMechanical properties ofsaline soil under the influence of different factorsrdquo FreseniusEnvironmental Bulletin vol 28 no 2A pp 1366ndash1373 2019

[16] L Wei S X Chai H Z Cai et al ldquoResearch on tensility ofwheat straw for reinforced materialrdquo Rock amp Soil Mechanicsvol 31 no 1 pp 128ndash132 2010

[17] L Wei S X Chai H Z Cai et al ldquoPhysical and mechanicalproperties of wheat straw and unconfined compressivestrength of reinforced inshore saline soil with wheat strawrdquoChina Civil Engineering Journal vol 43 no 3 pp 93ndash982010

[18] M Li S X Chai H P Du et al ldquoReasonable reinforcementposition and shear strength model of reinforced saline soilwith wheat straw and limerdquo Chinese Jourhal of Rock Me-chanics and Engineering vol 29 no sup 2 pp 3923ndash39292010

[19] P Wang S X Chai X Y Wang et al ldquoAnalysis of effectfactors of heavy compaction test for wheat straw-reinforcedsaline soilrdquo Rock and Soil Mechanics vol 32 no 2pp 448ndash452 2011

[20] L Wei S X Chai H Z Cai et al ldquoTriaxial shear strength anddeviatoric stress-strain of saline soils reinforced with wheatstrawsrdquo China Civil Engineering Journal vol 45 no 1pp 109ndash114 2012

[21] H Lu C G Yan X H Yang et al ldquoExperiment on anti-eroding property of reinforced loess with wheat strawrdquoJournal of Changrsquoan University (Natural Science Edition)vol 37 no 1 pp 24ndash32 2017

[22] J B Hao X MWei J Yao et al ldquoStrength characteristics andmesostructure of wheat straw einforced soilrdquo Journal of TongjiUniversity (Natural Science) vol 47 no 6 pp 764ndash831 2019

[23] GB50007-2011 Code for Design of Building foundationMinistry of Housing and Urban-Rural Development BeijingChina 2012

[24] JTG D30-2015 Specifications for Design of Highway Sub-grades China Communications Publishing amp Media Man-agement Co Ltd Beijing China 2016

[25] GBT 50123-1999 Standard for Soil Test Method Ministry ofConstruction Beijing China 2000

14 Advances in Materials Science and Engineering

0 10 20 30 40 50 60 7000

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing aging (day)

0 cement content

(a)

000 10 20 30 40 50 60 70

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

Curing aging (day)

3 cement content

(b)

00

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing aging (day)

6 cement content

(c)

01

02

03

04

05

06

07

Peak

stre

ss σ

(MPa

)

0 10 20 30 40 50 60 70Curing aging (day)

9 cement content

(d)

Figure 13 Curve fitting for the relationship between curing periods and unconfined compressive strength of specimens mixed with 02wheat straw and different cement content (a) 0 cement content (b) 3 cement content (c) 6 cement content (d) 9 cement content

Table 5 pu p0 and α in equation (3) obtained by fitting method

Cement content () Wheat straw content () A pu p0 Correlation coefficient (R)

0

000 014588 043154 009152 098592010 014516 044304 009313 098594015 014618 044932 009624 098513020 014544 045447 010006 098573025 014475 046229 010691 098532

3

000 014579 058251 012124 098826010 014551 058510 012383 098837015 014540 058738 012611 098756020 014464 059306 013179 098620025 014476 059871 013744 098922

6

000 014398 073439 015303 098871010 014613 073703 015567 098887015 014558 074029 015893 098998020 014623 074398 016262 098928025 014489 074994 016858 099096

9

000 014483 089900 018327 099765010 014643 090140 018567 099796015 014568 090410 018837 099796020 014456 090841 019268 099864025 014483 091405 019832 099801

Advances in Materials Science and Engineering 9

Table 6 p0 and pu in equation (4) obtained by fitting method

Cement content () Wheat straw content () α pu p0 Correlation coefficient (R)

0

000

0145

042040 008205 098389010 043203 008498 098396015 043892 008708 098338020 044639 009132 098464025 045536 009759 098451

3

000

0145

056306 011459 098765010 057668 011623 098763015 058741 011906 098752020 059589 012309 098607025 061033 012917 098894

6

000

0145

075501 014632 098870010 075883 014825 098885015 076059 015161 098966020 076642 015566 098839025 078146 016166 099062

9

000

0145

093233 018034 099679010 094507 018203 099703015 095207 018589 099711020 095780 018931 099748025 096357 019594 099705

000

002

004

006

008

010

012

014

016

018

020

022

024

026

0080

0085

0090

0095

0100

P 0 (M

Pa)

Wheat straw content as ()

0 cement content

(a)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0110

0115

0120

0125

0130

3 cement content

(b)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0140

0145

0150

0155

0160

0165

0170

6 cement content

(c)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0175

0180

0185

0190

0195

0200

9 cement content

(d)

Figure 14 Curve fitting for the relationship between p0 and wheat straw content for different cement content (a) 0 cement content (b)3 cement content (c) 6 cement content (d) 9 cement content

10 Advances in Materials Science and Engineering

As can be seen from Table 10 a is in the range of 000832to 000861 showing that the change of a is very little -emean value for a is 000849 and the value of a in equation(10) is replaced by 00085 then equation (10) can beexpressed as

pu 00085 middot eminus ξmiddotas( ) + pui (11)

-en based on equation (11) and the data in Table 9 ςand pui can be further obtained by fitting method as shownin Table 11

Figure 17 shows the curve fitting for the relationshipbetween ξ and cement content and the following expressioncan describe the curve fitting

ξ a1 middot eminus b1 middotac( ) + ξ0 (12)

where a1 is the coefficient related to curve growth ac iscement content b1 is the exponent ξ0 is initial value of ξonly related to cement content Based on the data fromTable 11 a1 b1 and ξ0 can be obtained by fitting methodwhich are 1514 0096 and 5002 respectively -ereforeequation (12) can be expressed as

ξ 1514 middot eminus 0096middotac( ) + 5002 (13)

Moreover Figure 18 shows the curve fitting for therelationship between pui and cement content -e followingexpression can describe the fitting curve in Figure 18

pui 00571 middot ac + 040226 (14)

-erefore substituting equations (13) and (14) intoequation (11) it can be expressed as

pu 00085 middot eminus 1514middote minus0096middotac( )+5002( 1113857middotas( 1113857

+ 00571 middot ac + 040226

(15)

p0 and pu in equation (4) are replaced by equations (9) and(15) then equation (4) can be expressed as

p 00085 middot e minus 1514middote minus0096middotac( )+5002( 1113857middotas( + 004624 middot ac + 004624

minus00017 middot e9356middotas

⎛⎝ ⎞⎠

middot 1 minus e(minus 0145middott)

1113872 1113873 + 000165 middot e9356middotas + 001086 middot ac + 008014

(16)

From the published literature [16] ultimate unconfinedcompressive strength increased firstly with adding wheatstraws however with further increasing of wheat strawscontent the ultimate unconfined compressive strength de-creased In test we cannot find the maximum wheat strawscontent and therefore when using equation (16) to predictthe ultimate unconfined compressive strength wheat straws

Table 7 η b and p0i in equation (5) obtained by fitting method

Cement content () Η b p0i Correlation coefficient (R)

0 000176 892416 008035 0999653 000159 910512 011308 0998956 000188 938257 014420 0998449 000167 1008636 017843 099709

Table 8 b and p0i in equation (6) obtained by fitting method

Cement content b p0i Correlation coefficient (R)

0 934882 008053 0999623 924118 011252 0998586 939121 014456 0998329 944322 017848 099709

00 20 40 60 80 100

008

010

012

014

016

018

020

P 0i (

MPa

)

Cement content ()

Figure 15 Curve fitting for the relationship between p0i andcement content

Table 9 pu in equation (3) obtained with equation (4)

Cement content () Wheat straw content() α pu

0

000

0145

042179010 043434015 043685020 044085025 045725

3

000

0145

056437010 057692015 058943020 059343025 061983

6

000

0145

075695010 075950015 076201020 076601025 078241

9

000

0145

092953010 094208015 095459020 095859025 096499

Advances in Materials Science and Engineering 11

content cannot exceed 025 by weight of saline-alkalinesoils In addition when cement content in specimens isgreater than 9 by weight of saline-alkaline soils we cannotperform a series of tests to obtain the influence of cementcontent on ultimate unconfined compressive strength andtherefore in the application of equation (16) cement content

should be less than 9 Moreover for equation (16) derivedfrom the test on specimens with optimum water contentwhen using it to predict the ultimate unconfined com-pressive strength for specimens the range of optimum watercontent for specimens should fall into 127sim145 byweight of saline-alkaline soils

0 cement content

041504200425043004350440044504500455

04650460

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(a)

3 cement content

030010 015 020 025005000Wheat straw content ()

056005650570057505800585059005950600060506100615062006250630

P u (M

Pa)

(b)

0750

0755

0760

0765

0770

0775

0780

0785

0790

6 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(c)

09200925093009350940094509500955096009650970

9 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(d)

Figure 16 Curve fitting for the relationship between pu and wheat straw content for different cement content (a) 0 cement content (b)3 cement content (c) 6 cement content (d) 9 cement content

Table 10 a ς and pui in equation (10) obtained by fitting method

Cement content a ς pui Correlation coefficient (R)

0 000861 639527 041324 0998703 000832 689803 055693 0998376 000857 745161 075670 0998659 000848 832193 091686 099934

Table 11 ς and pui in equation (11) obtained by fitting method

Cement content () a ς pui Correlation coefficient (R)

0

00085

651373 041364 0998693 702611 055628 0998356 768670 074533 0959769 858824 092165 099841

12 Advances in Materials Science and Engineering

34 Validity of Derived Equation (16) for Unconfined Com-pressive Strength of Specimens In order to obtain the reli-ability of derived equation (16) for unconfined compressivestrength of specimens the results from derived equation (16)should be compared with those from tests Based onequation (16) unconfined compressive strength of speci-mens mixed with 6 cement content and 02 wheat strawcontent for different curing periods can be obtained asshown in Table 12 In addition test results for unconfinedcompressive strength of specimens mixed with 6 cementcontent and 02 wheat straw content for different curingperiods are also shown in Table 12

As can be seen from Table 12 most of the deviation forunconfined compression strength falls in the range of260sim300 and the maximum deviation for unconfinedcompression strength can reach 316 when curing period is3 days -erefore compared with the test results the ac-curacy of results from the derived equation (16) is not veryhigh also indicating that equation (16) is only applicable tothe approximate evaluation of unconfined compression

strength of saline-alkaline soils In this paper we onlycompare the test result for specimens with combination ofwheat straw content and cement content already used in thecurrent study When using equation (16) to predict theunconfined compression strength of specimens with anothercombination of wheat straw content and cement contentother than what had been already used in the current studyspecimens should be in the state of maximum densitytherefore compaction tests should be firstly carried out toobtain the optimal moisture content of the specimens

4 Conclusions

In this study a series of tests are conducted to study theeffects of wheat straw and cement on the unconfinedcompression strength of specimens -e effect of wheatstraw and cement inclusions and curing periods on un-confined compression strength is determined -e followingconclusions are derived from these tests

-e inclusion of wheat straw within saline-alkaline soilsand saline-alkaline soils mixed with cement causes an in-crease in unconfined compression strength Increasingwheat straw content can increase the peak axial stress andweaken the brittle behavior of saline-alkaline soils mixedwith cement Moreover unconfined compression strengthof specimens increases with increasing curing periods It isknown that the interface roughness for wheat straw plays animportant role in reinforcing the soil Although it is animportant subject no attempt has yet been made to de-termine the optimum degree of the interface roughness Inaddition based on the data obtained from unconfinedcompression strength test a formula for predicting theunconfined compression strength of specimens related tocement content wheat straw content curing periods and soforth is put forward Compared with test results equation(16) is only applicable to the approximate evaluation ofunconfined compression strength of specimens

In addition in the present study we cannot obtain theinfluence of wheat straw content greater than 025 andorcement content greater than 9 on unconfined compressionstrength of specimens of specimens -erefore the appli-cation scope of equation (16) is limited If more test results ofunconfined compression strength of specimens mixed withwheat straw content greater than 025 andor cementcontent greater than 9 are obtained the application ofequation (16) will be more extensive in predicting the un-confined compression strength of specimens with optimalmoisture content Moreover only unconfined compression

00 20 40 60 80 10050

55

60

65

70

75

80

85

90

Cement content ()

ξ

Figure 17 Curve fitting for the relationship between ξ and cementcontent

00 20 40 60 80 100Cement content ()

10

09

08

07

06

05

04

03

02

01

00

p ui (

MPa

)

Figure 18 Curve fitting for the relationship between pui and ce-ment content

Table 12 Unconfined compression strength obtained from testand calculated value by equation (16)

Curingdays

Calculated value(MPa)

Test result(MPa)

Deviation()

3 0179 0136 3167 0398 0312 27614 0581 0449 29428 0582 0461 26256 0681 0529 286

Advances in Materials Science and Engineering 13

strength tests have been conducted on specimensmixed withwheat straw and cement -erefore investigations should becarried out further through other strength tests like directshear tests triaxial shear tests and so forth to study theinfluence of wheat straw on strength of specimens

Data Availability

-e data used to support the findings of this study are in-cluded within the article

Conflicts of Interest

-e authors declare no conflicts of interest with respect tothe research authorship andor publication of this article

Acknowledgments

-is work was financially supported by National NaturalScience Foundation of China (Grant no 51908430) Doc-toral Scientific Fund Project of Weifang University (Grantno 2017BS14) and Science and Technology Project of High-Tech Zone in Weifang (Grant no 2019KJHM09)

References

[1] R L Michalowski and J Cermak ldquoTriaxial compression ofsand reinforced with fibersrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 129 no 2 pp 125ndash1362003

[2] T Yetimoglu M Inanir and O Esatinanir ldquoA study onbearing capacity of randomly distributed fiber-reinforcedsand fills overlying soft clayrdquo Geotextiles and Geomembranesvol 23 no 2 pp 174ndash183 2005

[3] T Park and S Tan ldquoEnhanced performance of reinforced soilwalls by the inclusion of short fiberrdquo Geotextiles and Geo-membranes vol 23 no 4 pp 348ndash361 2005

[4] C Tang B Shi W Gao F Chen and Y Cai ldquoStrength andmechanical behavior of short polypropylene fiber reinforcedand cement stabilized clayey soilrdquo Geotextiles and Geo-membranes vol 25 no 3 pp 194ndash202 2007

[5] S Salah N Shadi and F Fadi ldquoShear strength of fiber-reinforced sandsrdquo Journal of Geotechnical and Geo-environmental Engineering vol 136 no 3 pp 490ndash499 2010

[6] G A Santiago C Franco N C Consoli and V R BotaroldquoStudy of mechanical behavior of a sand soil reinforced withcuraua treated fibers with asphaltrdquo Materials Science Forumvol 730-732 pp 319ndash324 2012

[7] J Prabakar and R S Sridhar ldquoEffect of random inclusion ofsisal fibre on strength behaviour of soilrdquo Construction andBuilding Materials vol 16 no 2 pp 123ndash131 2002

[8] C Mahipal Singh M Satyendra and M BijayanandaldquoPerformance evaluation of silty sand subgrade reinforcedwith fly ash and fibrerdquoGeotextiles and Geomembranes vol 26no 5 pp 429ndash435 2008

[9] M Bouhicha F Aouissi and S Kenai ldquoPerformance ofcomposite soil reinforced with barley strawrdquo Cement andConcrete Composites vol 27 no 5 pp 617ndash621 2005

[10] N C Consoli M D T Casagrande P D M Prietto andA n -ome ldquoPlate load test on fiber-reinforced soilrdquo Journalof Geotechnical and Geoenvironmental Engineering vol 129no 10 pp 951ndash955 2003

[11] J Yao Experimental Study on Strength Characteristics ofWheat Straw Reinforced soil Changrsquoan University XirsquoanChina 2017

[12] A Adili A Rafig S Giovanni et al ldquoStrength of soil rein-forced with fiber materials (papyrus)rdquo Soil Mechanics andFoundation Engineering vol 48 no 6 pp 241ndash247 2012

[13] Y L Qian ldquoExperimentresearch of mechanical properties ofimproved saline soilrdquo Geotechnical Investigation and Sur-veying vol 5 pp 1ndash4 2003

[14] X S Wang H Q Zhang and M Xue ldquoRoad disease andtreatment in saline soil areardquo Journal of Tongji Universityvol 31 no 10 pp 1178ndash1182 2003

[15] Q LWang Y Chao Y F Liu et al ldquoMechanical properties ofsaline soil under the influence of different factorsrdquo FreseniusEnvironmental Bulletin vol 28 no 2A pp 1366ndash1373 2019

[16] L Wei S X Chai H Z Cai et al ldquoResearch on tensility ofwheat straw for reinforced materialrdquo Rock amp Soil Mechanicsvol 31 no 1 pp 128ndash132 2010

[17] L Wei S X Chai H Z Cai et al ldquoPhysical and mechanicalproperties of wheat straw and unconfined compressivestrength of reinforced inshore saline soil with wheat strawrdquoChina Civil Engineering Journal vol 43 no 3 pp 93ndash982010

[18] M Li S X Chai H P Du et al ldquoReasonable reinforcementposition and shear strength model of reinforced saline soilwith wheat straw and limerdquo Chinese Jourhal of Rock Me-chanics and Engineering vol 29 no sup 2 pp 3923ndash39292010

[19] P Wang S X Chai X Y Wang et al ldquoAnalysis of effectfactors of heavy compaction test for wheat straw-reinforcedsaline soilrdquo Rock and Soil Mechanics vol 32 no 2pp 448ndash452 2011

[20] L Wei S X Chai H Z Cai et al ldquoTriaxial shear strength anddeviatoric stress-strain of saline soils reinforced with wheatstrawsrdquo China Civil Engineering Journal vol 45 no 1pp 109ndash114 2012

[21] H Lu C G Yan X H Yang et al ldquoExperiment on anti-eroding property of reinforced loess with wheat strawrdquoJournal of Changrsquoan University (Natural Science Edition)vol 37 no 1 pp 24ndash32 2017

[22] J B Hao X MWei J Yao et al ldquoStrength characteristics andmesostructure of wheat straw einforced soilrdquo Journal of TongjiUniversity (Natural Science) vol 47 no 6 pp 764ndash831 2019

[23] GB50007-2011 Code for Design of Building foundationMinistry of Housing and Urban-Rural Development BeijingChina 2012

[24] JTG D30-2015 Specifications for Design of Highway Sub-grades China Communications Publishing amp Media Man-agement Co Ltd Beijing China 2016

[25] GBT 50123-1999 Standard for Soil Test Method Ministry ofConstruction Beijing China 2000

14 Advances in Materials Science and Engineering

Table 6 p0 and pu in equation (4) obtained by fitting method

Cement content () Wheat straw content () α pu p0 Correlation coefficient (R)

0

000

0145

042040 008205 098389010 043203 008498 098396015 043892 008708 098338020 044639 009132 098464025 045536 009759 098451

3

000

0145

056306 011459 098765010 057668 011623 098763015 058741 011906 098752020 059589 012309 098607025 061033 012917 098894

6

000

0145

075501 014632 098870010 075883 014825 098885015 076059 015161 098966020 076642 015566 098839025 078146 016166 099062

9

000

0145

093233 018034 099679010 094507 018203 099703015 095207 018589 099711020 095780 018931 099748025 096357 019594 099705

000

002

004

006

008

010

012

014

016

018

020

022

024

026

0080

0085

0090

0095

0100

P 0 (M

Pa)

Wheat straw content as ()

0 cement content

(a)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0110

0115

0120

0125

0130

3 cement content

(b)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0140

0145

0150

0155

0160

0165

0170

6 cement content

(c)

P 0 (M

Pa)

000

002

004

006

008

010

012

014

016

018

020

022

024

028

026

Wheat straw content as ()

0175

0180

0185

0190

0195

0200

9 cement content

(d)

Figure 14 Curve fitting for the relationship between p0 and wheat straw content for different cement content (a) 0 cement content (b)3 cement content (c) 6 cement content (d) 9 cement content

10 Advances in Materials Science and Engineering

As can be seen from Table 10 a is in the range of 000832to 000861 showing that the change of a is very little -emean value for a is 000849 and the value of a in equation(10) is replaced by 00085 then equation (10) can beexpressed as

pu 00085 middot eminus ξmiddotas( ) + pui (11)

-en based on equation (11) and the data in Table 9 ςand pui can be further obtained by fitting method as shownin Table 11

Figure 17 shows the curve fitting for the relationshipbetween ξ and cement content and the following expressioncan describe the curve fitting

ξ a1 middot eminus b1 middotac( ) + ξ0 (12)

where a1 is the coefficient related to curve growth ac iscement content b1 is the exponent ξ0 is initial value of ξonly related to cement content Based on the data fromTable 11 a1 b1 and ξ0 can be obtained by fitting methodwhich are 1514 0096 and 5002 respectively -ereforeequation (12) can be expressed as

ξ 1514 middot eminus 0096middotac( ) + 5002 (13)

Moreover Figure 18 shows the curve fitting for therelationship between pui and cement content -e followingexpression can describe the fitting curve in Figure 18

pui 00571 middot ac + 040226 (14)

-erefore substituting equations (13) and (14) intoequation (11) it can be expressed as

pu 00085 middot eminus 1514middote minus0096middotac( )+5002( 1113857middotas( 1113857

+ 00571 middot ac + 040226

(15)

p0 and pu in equation (4) are replaced by equations (9) and(15) then equation (4) can be expressed as

p 00085 middot e minus 1514middote minus0096middotac( )+5002( 1113857middotas( + 004624 middot ac + 004624

minus00017 middot e9356middotas

⎛⎝ ⎞⎠

middot 1 minus e(minus 0145middott)

1113872 1113873 + 000165 middot e9356middotas + 001086 middot ac + 008014

(16)

From the published literature [16] ultimate unconfinedcompressive strength increased firstly with adding wheatstraws however with further increasing of wheat strawscontent the ultimate unconfined compressive strength de-creased In test we cannot find the maximum wheat strawscontent and therefore when using equation (16) to predictthe ultimate unconfined compressive strength wheat straws

Table 7 η b and p0i in equation (5) obtained by fitting method

Cement content () Η b p0i Correlation coefficient (R)

0 000176 892416 008035 0999653 000159 910512 011308 0998956 000188 938257 014420 0998449 000167 1008636 017843 099709

Table 8 b and p0i in equation (6) obtained by fitting method

Cement content b p0i Correlation coefficient (R)

0 934882 008053 0999623 924118 011252 0998586 939121 014456 0998329 944322 017848 099709

00 20 40 60 80 100

008

010

012

014

016

018

020

P 0i (

MPa

)

Cement content ()

Figure 15 Curve fitting for the relationship between p0i andcement content

Table 9 pu in equation (3) obtained with equation (4)

Cement content () Wheat straw content() α pu

0

000

0145

042179010 043434015 043685020 044085025 045725

3

000

0145

056437010 057692015 058943020 059343025 061983

6

000

0145

075695010 075950015 076201020 076601025 078241

9

000

0145

092953010 094208015 095459020 095859025 096499

Advances in Materials Science and Engineering 11

content cannot exceed 025 by weight of saline-alkalinesoils In addition when cement content in specimens isgreater than 9 by weight of saline-alkaline soils we cannotperform a series of tests to obtain the influence of cementcontent on ultimate unconfined compressive strength andtherefore in the application of equation (16) cement content

should be less than 9 Moreover for equation (16) derivedfrom the test on specimens with optimum water contentwhen using it to predict the ultimate unconfined com-pressive strength for specimens the range of optimum watercontent for specimens should fall into 127sim145 byweight of saline-alkaline soils

0 cement content

041504200425043004350440044504500455

04650460

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(a)

3 cement content

030010 015 020 025005000Wheat straw content ()

056005650570057505800585059005950600060506100615062006250630

P u (M

Pa)

(b)

0750

0755

0760

0765

0770

0775

0780

0785

0790

6 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(c)

09200925093009350940094509500955096009650970

9 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(d)

Figure 16 Curve fitting for the relationship between pu and wheat straw content for different cement content (a) 0 cement content (b)3 cement content (c) 6 cement content (d) 9 cement content

Table 10 a ς and pui in equation (10) obtained by fitting method

Cement content a ς pui Correlation coefficient (R)

0 000861 639527 041324 0998703 000832 689803 055693 0998376 000857 745161 075670 0998659 000848 832193 091686 099934

Table 11 ς and pui in equation (11) obtained by fitting method

Cement content () a ς pui Correlation coefficient (R)

0

00085

651373 041364 0998693 702611 055628 0998356 768670 074533 0959769 858824 092165 099841

12 Advances in Materials Science and Engineering

34 Validity of Derived Equation (16) for Unconfined Com-pressive Strength of Specimens In order to obtain the reli-ability of derived equation (16) for unconfined compressivestrength of specimens the results from derived equation (16)should be compared with those from tests Based onequation (16) unconfined compressive strength of speci-mens mixed with 6 cement content and 02 wheat strawcontent for different curing periods can be obtained asshown in Table 12 In addition test results for unconfinedcompressive strength of specimens mixed with 6 cementcontent and 02 wheat straw content for different curingperiods are also shown in Table 12

As can be seen from Table 12 most of the deviation forunconfined compression strength falls in the range of260sim300 and the maximum deviation for unconfinedcompression strength can reach 316 when curing period is3 days -erefore compared with the test results the ac-curacy of results from the derived equation (16) is not veryhigh also indicating that equation (16) is only applicable tothe approximate evaluation of unconfined compression

strength of saline-alkaline soils In this paper we onlycompare the test result for specimens with combination ofwheat straw content and cement content already used in thecurrent study When using equation (16) to predict theunconfined compression strength of specimens with anothercombination of wheat straw content and cement contentother than what had been already used in the current studyspecimens should be in the state of maximum densitytherefore compaction tests should be firstly carried out toobtain the optimal moisture content of the specimens

4 Conclusions

In this study a series of tests are conducted to study theeffects of wheat straw and cement on the unconfinedcompression strength of specimens -e effect of wheatstraw and cement inclusions and curing periods on un-confined compression strength is determined -e followingconclusions are derived from these tests

-e inclusion of wheat straw within saline-alkaline soilsand saline-alkaline soils mixed with cement causes an in-crease in unconfined compression strength Increasingwheat straw content can increase the peak axial stress andweaken the brittle behavior of saline-alkaline soils mixedwith cement Moreover unconfined compression strengthof specimens increases with increasing curing periods It isknown that the interface roughness for wheat straw plays animportant role in reinforcing the soil Although it is animportant subject no attempt has yet been made to de-termine the optimum degree of the interface roughness Inaddition based on the data obtained from unconfinedcompression strength test a formula for predicting theunconfined compression strength of specimens related tocement content wheat straw content curing periods and soforth is put forward Compared with test results equation(16) is only applicable to the approximate evaluation ofunconfined compression strength of specimens

In addition in the present study we cannot obtain theinfluence of wheat straw content greater than 025 andorcement content greater than 9 on unconfined compressionstrength of specimens of specimens -erefore the appli-cation scope of equation (16) is limited If more test results ofunconfined compression strength of specimens mixed withwheat straw content greater than 025 andor cementcontent greater than 9 are obtained the application ofequation (16) will be more extensive in predicting the un-confined compression strength of specimens with optimalmoisture content Moreover only unconfined compression

00 20 40 60 80 10050

55

60

65

70

75

80

85

90

Cement content ()

ξ

Figure 17 Curve fitting for the relationship between ξ and cementcontent

00 20 40 60 80 100Cement content ()

10

09

08

07

06

05

04

03

02

01

00

p ui (

MPa

)

Figure 18 Curve fitting for the relationship between pui and ce-ment content

Table 12 Unconfined compression strength obtained from testand calculated value by equation (16)

Curingdays

Calculated value(MPa)

Test result(MPa)

Deviation()

3 0179 0136 3167 0398 0312 27614 0581 0449 29428 0582 0461 26256 0681 0529 286

Advances in Materials Science and Engineering 13

strength tests have been conducted on specimensmixed withwheat straw and cement -erefore investigations should becarried out further through other strength tests like directshear tests triaxial shear tests and so forth to study theinfluence of wheat straw on strength of specimens

Data Availability

-e data used to support the findings of this study are in-cluded within the article

Conflicts of Interest

-e authors declare no conflicts of interest with respect tothe research authorship andor publication of this article

Acknowledgments

-is work was financially supported by National NaturalScience Foundation of China (Grant no 51908430) Doc-toral Scientific Fund Project of Weifang University (Grantno 2017BS14) and Science and Technology Project of High-Tech Zone in Weifang (Grant no 2019KJHM09)

References

[1] R L Michalowski and J Cermak ldquoTriaxial compression ofsand reinforced with fibersrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 129 no 2 pp 125ndash1362003

[2] T Yetimoglu M Inanir and O Esatinanir ldquoA study onbearing capacity of randomly distributed fiber-reinforcedsand fills overlying soft clayrdquo Geotextiles and Geomembranesvol 23 no 2 pp 174ndash183 2005

[3] T Park and S Tan ldquoEnhanced performance of reinforced soilwalls by the inclusion of short fiberrdquo Geotextiles and Geo-membranes vol 23 no 4 pp 348ndash361 2005

[4] C Tang B Shi W Gao F Chen and Y Cai ldquoStrength andmechanical behavior of short polypropylene fiber reinforcedand cement stabilized clayey soilrdquo Geotextiles and Geo-membranes vol 25 no 3 pp 194ndash202 2007

[5] S Salah N Shadi and F Fadi ldquoShear strength of fiber-reinforced sandsrdquo Journal of Geotechnical and Geo-environmental Engineering vol 136 no 3 pp 490ndash499 2010

[6] G A Santiago C Franco N C Consoli and V R BotaroldquoStudy of mechanical behavior of a sand soil reinforced withcuraua treated fibers with asphaltrdquo Materials Science Forumvol 730-732 pp 319ndash324 2012

[7] J Prabakar and R S Sridhar ldquoEffect of random inclusion ofsisal fibre on strength behaviour of soilrdquo Construction andBuilding Materials vol 16 no 2 pp 123ndash131 2002

[8] C Mahipal Singh M Satyendra and M BijayanandaldquoPerformance evaluation of silty sand subgrade reinforcedwith fly ash and fibrerdquoGeotextiles and Geomembranes vol 26no 5 pp 429ndash435 2008

[9] M Bouhicha F Aouissi and S Kenai ldquoPerformance ofcomposite soil reinforced with barley strawrdquo Cement andConcrete Composites vol 27 no 5 pp 617ndash621 2005

[10] N C Consoli M D T Casagrande P D M Prietto andA n -ome ldquoPlate load test on fiber-reinforced soilrdquo Journalof Geotechnical and Geoenvironmental Engineering vol 129no 10 pp 951ndash955 2003

[11] J Yao Experimental Study on Strength Characteristics ofWheat Straw Reinforced soil Changrsquoan University XirsquoanChina 2017

[12] A Adili A Rafig S Giovanni et al ldquoStrength of soil rein-forced with fiber materials (papyrus)rdquo Soil Mechanics andFoundation Engineering vol 48 no 6 pp 241ndash247 2012

[13] Y L Qian ldquoExperimentresearch of mechanical properties ofimproved saline soilrdquo Geotechnical Investigation and Sur-veying vol 5 pp 1ndash4 2003

[14] X S Wang H Q Zhang and M Xue ldquoRoad disease andtreatment in saline soil areardquo Journal of Tongji Universityvol 31 no 10 pp 1178ndash1182 2003

[15] Q LWang Y Chao Y F Liu et al ldquoMechanical properties ofsaline soil under the influence of different factorsrdquo FreseniusEnvironmental Bulletin vol 28 no 2A pp 1366ndash1373 2019

[16] L Wei S X Chai H Z Cai et al ldquoResearch on tensility ofwheat straw for reinforced materialrdquo Rock amp Soil Mechanicsvol 31 no 1 pp 128ndash132 2010

[17] L Wei S X Chai H Z Cai et al ldquoPhysical and mechanicalproperties of wheat straw and unconfined compressivestrength of reinforced inshore saline soil with wheat strawrdquoChina Civil Engineering Journal vol 43 no 3 pp 93ndash982010

[18] M Li S X Chai H P Du et al ldquoReasonable reinforcementposition and shear strength model of reinforced saline soilwith wheat straw and limerdquo Chinese Jourhal of Rock Me-chanics and Engineering vol 29 no sup 2 pp 3923ndash39292010

[19] P Wang S X Chai X Y Wang et al ldquoAnalysis of effectfactors of heavy compaction test for wheat straw-reinforcedsaline soilrdquo Rock and Soil Mechanics vol 32 no 2pp 448ndash452 2011

[20] L Wei S X Chai H Z Cai et al ldquoTriaxial shear strength anddeviatoric stress-strain of saline soils reinforced with wheatstrawsrdquo China Civil Engineering Journal vol 45 no 1pp 109ndash114 2012

[21] H Lu C G Yan X H Yang et al ldquoExperiment on anti-eroding property of reinforced loess with wheat strawrdquoJournal of Changrsquoan University (Natural Science Edition)vol 37 no 1 pp 24ndash32 2017

[22] J B Hao X MWei J Yao et al ldquoStrength characteristics andmesostructure of wheat straw einforced soilrdquo Journal of TongjiUniversity (Natural Science) vol 47 no 6 pp 764ndash831 2019

[23] GB50007-2011 Code for Design of Building foundationMinistry of Housing and Urban-Rural Development BeijingChina 2012

[24] JTG D30-2015 Specifications for Design of Highway Sub-grades China Communications Publishing amp Media Man-agement Co Ltd Beijing China 2016

[25] GBT 50123-1999 Standard for Soil Test Method Ministry ofConstruction Beijing China 2000

14 Advances in Materials Science and Engineering

As can be seen from Table 10 a is in the range of 000832to 000861 showing that the change of a is very little -emean value for a is 000849 and the value of a in equation(10) is replaced by 00085 then equation (10) can beexpressed as

pu 00085 middot eminus ξmiddotas( ) + pui (11)

-en based on equation (11) and the data in Table 9 ςand pui can be further obtained by fitting method as shownin Table 11

Figure 17 shows the curve fitting for the relationshipbetween ξ and cement content and the following expressioncan describe the curve fitting

ξ a1 middot eminus b1 middotac( ) + ξ0 (12)

where a1 is the coefficient related to curve growth ac iscement content b1 is the exponent ξ0 is initial value of ξonly related to cement content Based on the data fromTable 11 a1 b1 and ξ0 can be obtained by fitting methodwhich are 1514 0096 and 5002 respectively -ereforeequation (12) can be expressed as

ξ 1514 middot eminus 0096middotac( ) + 5002 (13)

Moreover Figure 18 shows the curve fitting for therelationship between pui and cement content -e followingexpression can describe the fitting curve in Figure 18

pui 00571 middot ac + 040226 (14)

-erefore substituting equations (13) and (14) intoequation (11) it can be expressed as

pu 00085 middot eminus 1514middote minus0096middotac( )+5002( 1113857middotas( 1113857

+ 00571 middot ac + 040226

(15)

p0 and pu in equation (4) are replaced by equations (9) and(15) then equation (4) can be expressed as

p 00085 middot e minus 1514middote minus0096middotac( )+5002( 1113857middotas( + 004624 middot ac + 004624

minus00017 middot e9356middotas

⎛⎝ ⎞⎠

middot 1 minus e(minus 0145middott)

1113872 1113873 + 000165 middot e9356middotas + 001086 middot ac + 008014

(16)

From the published literature [16] ultimate unconfinedcompressive strength increased firstly with adding wheatstraws however with further increasing of wheat strawscontent the ultimate unconfined compressive strength de-creased In test we cannot find the maximum wheat strawscontent and therefore when using equation (16) to predictthe ultimate unconfined compressive strength wheat straws

Table 7 η b and p0i in equation (5) obtained by fitting method

Cement content () Η b p0i Correlation coefficient (R)

0 000176 892416 008035 0999653 000159 910512 011308 0998956 000188 938257 014420 0998449 000167 1008636 017843 099709

Table 8 b and p0i in equation (6) obtained by fitting method

Cement content b p0i Correlation coefficient (R)

0 934882 008053 0999623 924118 011252 0998586 939121 014456 0998329 944322 017848 099709

00 20 40 60 80 100

008

010

012

014

016

018

020

P 0i (

MPa

)

Cement content ()

Figure 15 Curve fitting for the relationship between p0i andcement content

Table 9 pu in equation (3) obtained with equation (4)

Cement content () Wheat straw content() α pu

0

000

0145

042179010 043434015 043685020 044085025 045725

3

000

0145

056437010 057692015 058943020 059343025 061983

6

000

0145

075695010 075950015 076201020 076601025 078241

9

000

0145

092953010 094208015 095459020 095859025 096499

Advances in Materials Science and Engineering 11

content cannot exceed 025 by weight of saline-alkalinesoils In addition when cement content in specimens isgreater than 9 by weight of saline-alkaline soils we cannotperform a series of tests to obtain the influence of cementcontent on ultimate unconfined compressive strength andtherefore in the application of equation (16) cement content

should be less than 9 Moreover for equation (16) derivedfrom the test on specimens with optimum water contentwhen using it to predict the ultimate unconfined com-pressive strength for specimens the range of optimum watercontent for specimens should fall into 127sim145 byweight of saline-alkaline soils

0 cement content

041504200425043004350440044504500455

04650460

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(a)

3 cement content

030010 015 020 025005000Wheat straw content ()

056005650570057505800585059005950600060506100615062006250630

P u (M

Pa)

(b)

0750

0755

0760

0765

0770

0775

0780

0785

0790

6 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(c)

09200925093009350940094509500955096009650970

9 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(d)

Figure 16 Curve fitting for the relationship between pu and wheat straw content for different cement content (a) 0 cement content (b)3 cement content (c) 6 cement content (d) 9 cement content

Table 10 a ς and pui in equation (10) obtained by fitting method

Cement content a ς pui Correlation coefficient (R)

0 000861 639527 041324 0998703 000832 689803 055693 0998376 000857 745161 075670 0998659 000848 832193 091686 099934

Table 11 ς and pui in equation (11) obtained by fitting method

Cement content () a ς pui Correlation coefficient (R)

0

00085

651373 041364 0998693 702611 055628 0998356 768670 074533 0959769 858824 092165 099841

12 Advances in Materials Science and Engineering

34 Validity of Derived Equation (16) for Unconfined Com-pressive Strength of Specimens In order to obtain the reli-ability of derived equation (16) for unconfined compressivestrength of specimens the results from derived equation (16)should be compared with those from tests Based onequation (16) unconfined compressive strength of speci-mens mixed with 6 cement content and 02 wheat strawcontent for different curing periods can be obtained asshown in Table 12 In addition test results for unconfinedcompressive strength of specimens mixed with 6 cementcontent and 02 wheat straw content for different curingperiods are also shown in Table 12

As can be seen from Table 12 most of the deviation forunconfined compression strength falls in the range of260sim300 and the maximum deviation for unconfinedcompression strength can reach 316 when curing period is3 days -erefore compared with the test results the ac-curacy of results from the derived equation (16) is not veryhigh also indicating that equation (16) is only applicable tothe approximate evaluation of unconfined compression

strength of saline-alkaline soils In this paper we onlycompare the test result for specimens with combination ofwheat straw content and cement content already used in thecurrent study When using equation (16) to predict theunconfined compression strength of specimens with anothercombination of wheat straw content and cement contentother than what had been already used in the current studyspecimens should be in the state of maximum densitytherefore compaction tests should be firstly carried out toobtain the optimal moisture content of the specimens

4 Conclusions

In this study a series of tests are conducted to study theeffects of wheat straw and cement on the unconfinedcompression strength of specimens -e effect of wheatstraw and cement inclusions and curing periods on un-confined compression strength is determined -e followingconclusions are derived from these tests

-e inclusion of wheat straw within saline-alkaline soilsand saline-alkaline soils mixed with cement causes an in-crease in unconfined compression strength Increasingwheat straw content can increase the peak axial stress andweaken the brittle behavior of saline-alkaline soils mixedwith cement Moreover unconfined compression strengthof specimens increases with increasing curing periods It isknown that the interface roughness for wheat straw plays animportant role in reinforcing the soil Although it is animportant subject no attempt has yet been made to de-termine the optimum degree of the interface roughness Inaddition based on the data obtained from unconfinedcompression strength test a formula for predicting theunconfined compression strength of specimens related tocement content wheat straw content curing periods and soforth is put forward Compared with test results equation(16) is only applicable to the approximate evaluation ofunconfined compression strength of specimens

In addition in the present study we cannot obtain theinfluence of wheat straw content greater than 025 andorcement content greater than 9 on unconfined compressionstrength of specimens of specimens -erefore the appli-cation scope of equation (16) is limited If more test results ofunconfined compression strength of specimens mixed withwheat straw content greater than 025 andor cementcontent greater than 9 are obtained the application ofequation (16) will be more extensive in predicting the un-confined compression strength of specimens with optimalmoisture content Moreover only unconfined compression

00 20 40 60 80 10050

55

60

65

70

75

80

85

90

Cement content ()

ξ

Figure 17 Curve fitting for the relationship between ξ and cementcontent

00 20 40 60 80 100Cement content ()

10

09

08

07

06

05

04

03

02

01

00

p ui (

MPa

)

Figure 18 Curve fitting for the relationship between pui and ce-ment content

Table 12 Unconfined compression strength obtained from testand calculated value by equation (16)

Curingdays

Calculated value(MPa)

Test result(MPa)

Deviation()

3 0179 0136 3167 0398 0312 27614 0581 0449 29428 0582 0461 26256 0681 0529 286

Advances in Materials Science and Engineering 13

strength tests have been conducted on specimensmixed withwheat straw and cement -erefore investigations should becarried out further through other strength tests like directshear tests triaxial shear tests and so forth to study theinfluence of wheat straw on strength of specimens

Data Availability

-e data used to support the findings of this study are in-cluded within the article

Conflicts of Interest

-e authors declare no conflicts of interest with respect tothe research authorship andor publication of this article

Acknowledgments

-is work was financially supported by National NaturalScience Foundation of China (Grant no 51908430) Doc-toral Scientific Fund Project of Weifang University (Grantno 2017BS14) and Science and Technology Project of High-Tech Zone in Weifang (Grant no 2019KJHM09)

References

[1] R L Michalowski and J Cermak ldquoTriaxial compression ofsand reinforced with fibersrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 129 no 2 pp 125ndash1362003

[2] T Yetimoglu M Inanir and O Esatinanir ldquoA study onbearing capacity of randomly distributed fiber-reinforcedsand fills overlying soft clayrdquo Geotextiles and Geomembranesvol 23 no 2 pp 174ndash183 2005

[3] T Park and S Tan ldquoEnhanced performance of reinforced soilwalls by the inclusion of short fiberrdquo Geotextiles and Geo-membranes vol 23 no 4 pp 348ndash361 2005

[4] C Tang B Shi W Gao F Chen and Y Cai ldquoStrength andmechanical behavior of short polypropylene fiber reinforcedand cement stabilized clayey soilrdquo Geotextiles and Geo-membranes vol 25 no 3 pp 194ndash202 2007

[5] S Salah N Shadi and F Fadi ldquoShear strength of fiber-reinforced sandsrdquo Journal of Geotechnical and Geo-environmental Engineering vol 136 no 3 pp 490ndash499 2010

[6] G A Santiago C Franco N C Consoli and V R BotaroldquoStudy of mechanical behavior of a sand soil reinforced withcuraua treated fibers with asphaltrdquo Materials Science Forumvol 730-732 pp 319ndash324 2012

[7] J Prabakar and R S Sridhar ldquoEffect of random inclusion ofsisal fibre on strength behaviour of soilrdquo Construction andBuilding Materials vol 16 no 2 pp 123ndash131 2002

[8] C Mahipal Singh M Satyendra and M BijayanandaldquoPerformance evaluation of silty sand subgrade reinforcedwith fly ash and fibrerdquoGeotextiles and Geomembranes vol 26no 5 pp 429ndash435 2008

[9] M Bouhicha F Aouissi and S Kenai ldquoPerformance ofcomposite soil reinforced with barley strawrdquo Cement andConcrete Composites vol 27 no 5 pp 617ndash621 2005

[10] N C Consoli M D T Casagrande P D M Prietto andA n -ome ldquoPlate load test on fiber-reinforced soilrdquo Journalof Geotechnical and Geoenvironmental Engineering vol 129no 10 pp 951ndash955 2003

[11] J Yao Experimental Study on Strength Characteristics ofWheat Straw Reinforced soil Changrsquoan University XirsquoanChina 2017

[12] A Adili A Rafig S Giovanni et al ldquoStrength of soil rein-forced with fiber materials (papyrus)rdquo Soil Mechanics andFoundation Engineering vol 48 no 6 pp 241ndash247 2012

[13] Y L Qian ldquoExperimentresearch of mechanical properties ofimproved saline soilrdquo Geotechnical Investigation and Sur-veying vol 5 pp 1ndash4 2003

[14] X S Wang H Q Zhang and M Xue ldquoRoad disease andtreatment in saline soil areardquo Journal of Tongji Universityvol 31 no 10 pp 1178ndash1182 2003

[15] Q LWang Y Chao Y F Liu et al ldquoMechanical properties ofsaline soil under the influence of different factorsrdquo FreseniusEnvironmental Bulletin vol 28 no 2A pp 1366ndash1373 2019

[16] L Wei S X Chai H Z Cai et al ldquoResearch on tensility ofwheat straw for reinforced materialrdquo Rock amp Soil Mechanicsvol 31 no 1 pp 128ndash132 2010

[17] L Wei S X Chai H Z Cai et al ldquoPhysical and mechanicalproperties of wheat straw and unconfined compressivestrength of reinforced inshore saline soil with wheat strawrdquoChina Civil Engineering Journal vol 43 no 3 pp 93ndash982010

[18] M Li S X Chai H P Du et al ldquoReasonable reinforcementposition and shear strength model of reinforced saline soilwith wheat straw and limerdquo Chinese Jourhal of Rock Me-chanics and Engineering vol 29 no sup 2 pp 3923ndash39292010

[19] P Wang S X Chai X Y Wang et al ldquoAnalysis of effectfactors of heavy compaction test for wheat straw-reinforcedsaline soilrdquo Rock and Soil Mechanics vol 32 no 2pp 448ndash452 2011

[20] L Wei S X Chai H Z Cai et al ldquoTriaxial shear strength anddeviatoric stress-strain of saline soils reinforced with wheatstrawsrdquo China Civil Engineering Journal vol 45 no 1pp 109ndash114 2012

[21] H Lu C G Yan X H Yang et al ldquoExperiment on anti-eroding property of reinforced loess with wheat strawrdquoJournal of Changrsquoan University (Natural Science Edition)vol 37 no 1 pp 24ndash32 2017

[22] J B Hao X MWei J Yao et al ldquoStrength characteristics andmesostructure of wheat straw einforced soilrdquo Journal of TongjiUniversity (Natural Science) vol 47 no 6 pp 764ndash831 2019

[23] GB50007-2011 Code for Design of Building foundationMinistry of Housing and Urban-Rural Development BeijingChina 2012

[24] JTG D30-2015 Specifications for Design of Highway Sub-grades China Communications Publishing amp Media Man-agement Co Ltd Beijing China 2016

[25] GBT 50123-1999 Standard for Soil Test Method Ministry ofConstruction Beijing China 2000

14 Advances in Materials Science and Engineering

content cannot exceed 025 by weight of saline-alkalinesoils In addition when cement content in specimens isgreater than 9 by weight of saline-alkaline soils we cannotperform a series of tests to obtain the influence of cementcontent on ultimate unconfined compressive strength andtherefore in the application of equation (16) cement content

should be less than 9 Moreover for equation (16) derivedfrom the test on specimens with optimum water contentwhen using it to predict the ultimate unconfined com-pressive strength for specimens the range of optimum watercontent for specimens should fall into 127sim145 byweight of saline-alkaline soils

0 cement content

041504200425043004350440044504500455

04650460

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(a)

3 cement content

030010 015 020 025005000Wheat straw content ()

056005650570057505800585059005950600060506100615062006250630

P u (M

Pa)

(b)

0750

0755

0760

0765

0770

0775

0780

0785

0790

6 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(c)

09200925093009350940094509500955096009650970

9 cement content

P u (M

Pa)

030010 015 020 025005000Wheat straw content ()

(d)

Figure 16 Curve fitting for the relationship between pu and wheat straw content for different cement content (a) 0 cement content (b)3 cement content (c) 6 cement content (d) 9 cement content

Table 10 a ς and pui in equation (10) obtained by fitting method

Cement content a ς pui Correlation coefficient (R)

0 000861 639527 041324 0998703 000832 689803 055693 0998376 000857 745161 075670 0998659 000848 832193 091686 099934

Table 11 ς and pui in equation (11) obtained by fitting method

Cement content () a ς pui Correlation coefficient (R)

0

00085

651373 041364 0998693 702611 055628 0998356 768670 074533 0959769 858824 092165 099841

12 Advances in Materials Science and Engineering

34 Validity of Derived Equation (16) for Unconfined Com-pressive Strength of Specimens In order to obtain the reli-ability of derived equation (16) for unconfined compressivestrength of specimens the results from derived equation (16)should be compared with those from tests Based onequation (16) unconfined compressive strength of speci-mens mixed with 6 cement content and 02 wheat strawcontent for different curing periods can be obtained asshown in Table 12 In addition test results for unconfinedcompressive strength of specimens mixed with 6 cementcontent and 02 wheat straw content for different curingperiods are also shown in Table 12

As can be seen from Table 12 most of the deviation forunconfined compression strength falls in the range of260sim300 and the maximum deviation for unconfinedcompression strength can reach 316 when curing period is3 days -erefore compared with the test results the ac-curacy of results from the derived equation (16) is not veryhigh also indicating that equation (16) is only applicable tothe approximate evaluation of unconfined compression

strength of saline-alkaline soils In this paper we onlycompare the test result for specimens with combination ofwheat straw content and cement content already used in thecurrent study When using equation (16) to predict theunconfined compression strength of specimens with anothercombination of wheat straw content and cement contentother than what had been already used in the current studyspecimens should be in the state of maximum densitytherefore compaction tests should be firstly carried out toobtain the optimal moisture content of the specimens

4 Conclusions

In this study a series of tests are conducted to study theeffects of wheat straw and cement on the unconfinedcompression strength of specimens -e effect of wheatstraw and cement inclusions and curing periods on un-confined compression strength is determined -e followingconclusions are derived from these tests

-e inclusion of wheat straw within saline-alkaline soilsand saline-alkaline soils mixed with cement causes an in-crease in unconfined compression strength Increasingwheat straw content can increase the peak axial stress andweaken the brittle behavior of saline-alkaline soils mixedwith cement Moreover unconfined compression strengthof specimens increases with increasing curing periods It isknown that the interface roughness for wheat straw plays animportant role in reinforcing the soil Although it is animportant subject no attempt has yet been made to de-termine the optimum degree of the interface roughness Inaddition based on the data obtained from unconfinedcompression strength test a formula for predicting theunconfined compression strength of specimens related tocement content wheat straw content curing periods and soforth is put forward Compared with test results equation(16) is only applicable to the approximate evaluation ofunconfined compression strength of specimens

In addition in the present study we cannot obtain theinfluence of wheat straw content greater than 025 andorcement content greater than 9 on unconfined compressionstrength of specimens of specimens -erefore the appli-cation scope of equation (16) is limited If more test results ofunconfined compression strength of specimens mixed withwheat straw content greater than 025 andor cementcontent greater than 9 are obtained the application ofequation (16) will be more extensive in predicting the un-confined compression strength of specimens with optimalmoisture content Moreover only unconfined compression

00 20 40 60 80 10050

55

60

65

70

75

80

85

90

Cement content ()

ξ

Figure 17 Curve fitting for the relationship between ξ and cementcontent

00 20 40 60 80 100Cement content ()

10

09

08

07

06

05

04

03

02

01

00

p ui (

MPa

)

Figure 18 Curve fitting for the relationship between pui and ce-ment content

Table 12 Unconfined compression strength obtained from testand calculated value by equation (16)

Curingdays

Calculated value(MPa)

Test result(MPa)

Deviation()

3 0179 0136 3167 0398 0312 27614 0581 0449 29428 0582 0461 26256 0681 0529 286

Advances in Materials Science and Engineering 13

strength tests have been conducted on specimensmixed withwheat straw and cement -erefore investigations should becarried out further through other strength tests like directshear tests triaxial shear tests and so forth to study theinfluence of wheat straw on strength of specimens

Data Availability

-e data used to support the findings of this study are in-cluded within the article

Conflicts of Interest

-e authors declare no conflicts of interest with respect tothe research authorship andor publication of this article

Acknowledgments

-is work was financially supported by National NaturalScience Foundation of China (Grant no 51908430) Doc-toral Scientific Fund Project of Weifang University (Grantno 2017BS14) and Science and Technology Project of High-Tech Zone in Weifang (Grant no 2019KJHM09)

References

[1] R L Michalowski and J Cermak ldquoTriaxial compression ofsand reinforced with fibersrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 129 no 2 pp 125ndash1362003

[2] T Yetimoglu M Inanir and O Esatinanir ldquoA study onbearing capacity of randomly distributed fiber-reinforcedsand fills overlying soft clayrdquo Geotextiles and Geomembranesvol 23 no 2 pp 174ndash183 2005

[3] T Park and S Tan ldquoEnhanced performance of reinforced soilwalls by the inclusion of short fiberrdquo Geotextiles and Geo-membranes vol 23 no 4 pp 348ndash361 2005

[4] C Tang B Shi W Gao F Chen and Y Cai ldquoStrength andmechanical behavior of short polypropylene fiber reinforcedand cement stabilized clayey soilrdquo Geotextiles and Geo-membranes vol 25 no 3 pp 194ndash202 2007

[5] S Salah N Shadi and F Fadi ldquoShear strength of fiber-reinforced sandsrdquo Journal of Geotechnical and Geo-environmental Engineering vol 136 no 3 pp 490ndash499 2010

[6] G A Santiago C Franco N C Consoli and V R BotaroldquoStudy of mechanical behavior of a sand soil reinforced withcuraua treated fibers with asphaltrdquo Materials Science Forumvol 730-732 pp 319ndash324 2012

[7] J Prabakar and R S Sridhar ldquoEffect of random inclusion ofsisal fibre on strength behaviour of soilrdquo Construction andBuilding Materials vol 16 no 2 pp 123ndash131 2002

[8] C Mahipal Singh M Satyendra and M BijayanandaldquoPerformance evaluation of silty sand subgrade reinforcedwith fly ash and fibrerdquoGeotextiles and Geomembranes vol 26no 5 pp 429ndash435 2008

[9] M Bouhicha F Aouissi and S Kenai ldquoPerformance ofcomposite soil reinforced with barley strawrdquo Cement andConcrete Composites vol 27 no 5 pp 617ndash621 2005

[10] N C Consoli M D T Casagrande P D M Prietto andA n -ome ldquoPlate load test on fiber-reinforced soilrdquo Journalof Geotechnical and Geoenvironmental Engineering vol 129no 10 pp 951ndash955 2003

[11] J Yao Experimental Study on Strength Characteristics ofWheat Straw Reinforced soil Changrsquoan University XirsquoanChina 2017

[12] A Adili A Rafig S Giovanni et al ldquoStrength of soil rein-forced with fiber materials (papyrus)rdquo Soil Mechanics andFoundation Engineering vol 48 no 6 pp 241ndash247 2012

[13] Y L Qian ldquoExperimentresearch of mechanical properties ofimproved saline soilrdquo Geotechnical Investigation and Sur-veying vol 5 pp 1ndash4 2003

[14] X S Wang H Q Zhang and M Xue ldquoRoad disease andtreatment in saline soil areardquo Journal of Tongji Universityvol 31 no 10 pp 1178ndash1182 2003

[15] Q LWang Y Chao Y F Liu et al ldquoMechanical properties ofsaline soil under the influence of different factorsrdquo FreseniusEnvironmental Bulletin vol 28 no 2A pp 1366ndash1373 2019

[16] L Wei S X Chai H Z Cai et al ldquoResearch on tensility ofwheat straw for reinforced materialrdquo Rock amp Soil Mechanicsvol 31 no 1 pp 128ndash132 2010

[17] L Wei S X Chai H Z Cai et al ldquoPhysical and mechanicalproperties of wheat straw and unconfined compressivestrength of reinforced inshore saline soil with wheat strawrdquoChina Civil Engineering Journal vol 43 no 3 pp 93ndash982010

[18] M Li S X Chai H P Du et al ldquoReasonable reinforcementposition and shear strength model of reinforced saline soilwith wheat straw and limerdquo Chinese Jourhal of Rock Me-chanics and Engineering vol 29 no sup 2 pp 3923ndash39292010

[19] P Wang S X Chai X Y Wang et al ldquoAnalysis of effectfactors of heavy compaction test for wheat straw-reinforcedsaline soilrdquo Rock and Soil Mechanics vol 32 no 2pp 448ndash452 2011

[20] L Wei S X Chai H Z Cai et al ldquoTriaxial shear strength anddeviatoric stress-strain of saline soils reinforced with wheatstrawsrdquo China Civil Engineering Journal vol 45 no 1pp 109ndash114 2012

[21] H Lu C G Yan X H Yang et al ldquoExperiment on anti-eroding property of reinforced loess with wheat strawrdquoJournal of Changrsquoan University (Natural Science Edition)vol 37 no 1 pp 24ndash32 2017

[22] J B Hao X MWei J Yao et al ldquoStrength characteristics andmesostructure of wheat straw einforced soilrdquo Journal of TongjiUniversity (Natural Science) vol 47 no 6 pp 764ndash831 2019

[23] GB50007-2011 Code for Design of Building foundationMinistry of Housing and Urban-Rural Development BeijingChina 2012

[24] JTG D30-2015 Specifications for Design of Highway Sub-grades China Communications Publishing amp Media Man-agement Co Ltd Beijing China 2016

[25] GBT 50123-1999 Standard for Soil Test Method Ministry ofConstruction Beijing China 2000

14 Advances in Materials Science and Engineering

34 Validity of Derived Equation (16) for Unconfined Com-pressive Strength of Specimens In order to obtain the reli-ability of derived equation (16) for unconfined compressivestrength of specimens the results from derived equation (16)should be compared with those from tests Based onequation (16) unconfined compressive strength of speci-mens mixed with 6 cement content and 02 wheat strawcontent for different curing periods can be obtained asshown in Table 12 In addition test results for unconfinedcompressive strength of specimens mixed with 6 cementcontent and 02 wheat straw content for different curingperiods are also shown in Table 12

As can be seen from Table 12 most of the deviation forunconfined compression strength falls in the range of260sim300 and the maximum deviation for unconfinedcompression strength can reach 316 when curing period is3 days -erefore compared with the test results the ac-curacy of results from the derived equation (16) is not veryhigh also indicating that equation (16) is only applicable tothe approximate evaluation of unconfined compression

strength of saline-alkaline soils In this paper we onlycompare the test result for specimens with combination ofwheat straw content and cement content already used in thecurrent study When using equation (16) to predict theunconfined compression strength of specimens with anothercombination of wheat straw content and cement contentother than what had been already used in the current studyspecimens should be in the state of maximum densitytherefore compaction tests should be firstly carried out toobtain the optimal moisture content of the specimens

4 Conclusions

In this study a series of tests are conducted to study theeffects of wheat straw and cement on the unconfinedcompression strength of specimens -e effect of wheatstraw and cement inclusions and curing periods on un-confined compression strength is determined -e followingconclusions are derived from these tests

-e inclusion of wheat straw within saline-alkaline soilsand saline-alkaline soils mixed with cement causes an in-crease in unconfined compression strength Increasingwheat straw content can increase the peak axial stress andweaken the brittle behavior of saline-alkaline soils mixedwith cement Moreover unconfined compression strengthof specimens increases with increasing curing periods It isknown that the interface roughness for wheat straw plays animportant role in reinforcing the soil Although it is animportant subject no attempt has yet been made to de-termine the optimum degree of the interface roughness Inaddition based on the data obtained from unconfinedcompression strength test a formula for predicting theunconfined compression strength of specimens related tocement content wheat straw content curing periods and soforth is put forward Compared with test results equation(16) is only applicable to the approximate evaluation ofunconfined compression strength of specimens

In addition in the present study we cannot obtain theinfluence of wheat straw content greater than 025 andorcement content greater than 9 on unconfined compressionstrength of specimens of specimens -erefore the appli-cation scope of equation (16) is limited If more test results ofunconfined compression strength of specimens mixed withwheat straw content greater than 025 andor cementcontent greater than 9 are obtained the application ofequation (16) will be more extensive in predicting the un-confined compression strength of specimens with optimalmoisture content Moreover only unconfined compression

00 20 40 60 80 10050

55

60

65

70

75

80

85

90

Cement content ()

ξ

Figure 17 Curve fitting for the relationship between ξ and cementcontent

00 20 40 60 80 100Cement content ()

10

09

08

07

06

05

04

03

02

01

00

p ui (

MPa

)

Figure 18 Curve fitting for the relationship between pui and ce-ment content

Table 12 Unconfined compression strength obtained from testand calculated value by equation (16)

Curingdays

Calculated value(MPa)

Test result(MPa)

Deviation()

3 0179 0136 3167 0398 0312 27614 0581 0449 29428 0582 0461 26256 0681 0529 286

Advances in Materials Science and Engineering 13

strength tests have been conducted on specimensmixed withwheat straw and cement -erefore investigations should becarried out further through other strength tests like directshear tests triaxial shear tests and so forth to study theinfluence of wheat straw on strength of specimens

Data Availability

-e data used to support the findings of this study are in-cluded within the article

Conflicts of Interest

-e authors declare no conflicts of interest with respect tothe research authorship andor publication of this article

Acknowledgments

-is work was financially supported by National NaturalScience Foundation of China (Grant no 51908430) Doc-toral Scientific Fund Project of Weifang University (Grantno 2017BS14) and Science and Technology Project of High-Tech Zone in Weifang (Grant no 2019KJHM09)

References

[1] R L Michalowski and J Cermak ldquoTriaxial compression ofsand reinforced with fibersrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 129 no 2 pp 125ndash1362003

[2] T Yetimoglu M Inanir and O Esatinanir ldquoA study onbearing capacity of randomly distributed fiber-reinforcedsand fills overlying soft clayrdquo Geotextiles and Geomembranesvol 23 no 2 pp 174ndash183 2005

[3] T Park and S Tan ldquoEnhanced performance of reinforced soilwalls by the inclusion of short fiberrdquo Geotextiles and Geo-membranes vol 23 no 4 pp 348ndash361 2005

[4] C Tang B Shi W Gao F Chen and Y Cai ldquoStrength andmechanical behavior of short polypropylene fiber reinforcedand cement stabilized clayey soilrdquo Geotextiles and Geo-membranes vol 25 no 3 pp 194ndash202 2007

[5] S Salah N Shadi and F Fadi ldquoShear strength of fiber-reinforced sandsrdquo Journal of Geotechnical and Geo-environmental Engineering vol 136 no 3 pp 490ndash499 2010

[6] G A Santiago C Franco N C Consoli and V R BotaroldquoStudy of mechanical behavior of a sand soil reinforced withcuraua treated fibers with asphaltrdquo Materials Science Forumvol 730-732 pp 319ndash324 2012

[7] J Prabakar and R S Sridhar ldquoEffect of random inclusion ofsisal fibre on strength behaviour of soilrdquo Construction andBuilding Materials vol 16 no 2 pp 123ndash131 2002

[8] C Mahipal Singh M Satyendra and M BijayanandaldquoPerformance evaluation of silty sand subgrade reinforcedwith fly ash and fibrerdquoGeotextiles and Geomembranes vol 26no 5 pp 429ndash435 2008

[9] M Bouhicha F Aouissi and S Kenai ldquoPerformance ofcomposite soil reinforced with barley strawrdquo Cement andConcrete Composites vol 27 no 5 pp 617ndash621 2005

[10] N C Consoli M D T Casagrande P D M Prietto andA n -ome ldquoPlate load test on fiber-reinforced soilrdquo Journalof Geotechnical and Geoenvironmental Engineering vol 129no 10 pp 951ndash955 2003

[11] J Yao Experimental Study on Strength Characteristics ofWheat Straw Reinforced soil Changrsquoan University XirsquoanChina 2017

[12] A Adili A Rafig S Giovanni et al ldquoStrength of soil rein-forced with fiber materials (papyrus)rdquo Soil Mechanics andFoundation Engineering vol 48 no 6 pp 241ndash247 2012

[13] Y L Qian ldquoExperimentresearch of mechanical properties ofimproved saline soilrdquo Geotechnical Investigation and Sur-veying vol 5 pp 1ndash4 2003

[14] X S Wang H Q Zhang and M Xue ldquoRoad disease andtreatment in saline soil areardquo Journal of Tongji Universityvol 31 no 10 pp 1178ndash1182 2003

[15] Q LWang Y Chao Y F Liu et al ldquoMechanical properties ofsaline soil under the influence of different factorsrdquo FreseniusEnvironmental Bulletin vol 28 no 2A pp 1366ndash1373 2019

[16] L Wei S X Chai H Z Cai et al ldquoResearch on tensility ofwheat straw for reinforced materialrdquo Rock amp Soil Mechanicsvol 31 no 1 pp 128ndash132 2010

[17] L Wei S X Chai H Z Cai et al ldquoPhysical and mechanicalproperties of wheat straw and unconfined compressivestrength of reinforced inshore saline soil with wheat strawrdquoChina Civil Engineering Journal vol 43 no 3 pp 93ndash982010

[18] M Li S X Chai H P Du et al ldquoReasonable reinforcementposition and shear strength model of reinforced saline soilwith wheat straw and limerdquo Chinese Jourhal of Rock Me-chanics and Engineering vol 29 no sup 2 pp 3923ndash39292010

[19] P Wang S X Chai X Y Wang et al ldquoAnalysis of effectfactors of heavy compaction test for wheat straw-reinforcedsaline soilrdquo Rock and Soil Mechanics vol 32 no 2pp 448ndash452 2011

[20] L Wei S X Chai H Z Cai et al ldquoTriaxial shear strength anddeviatoric stress-strain of saline soils reinforced with wheatstrawsrdquo China Civil Engineering Journal vol 45 no 1pp 109ndash114 2012

[21] H Lu C G Yan X H Yang et al ldquoExperiment on anti-eroding property of reinforced loess with wheat strawrdquoJournal of Changrsquoan University (Natural Science Edition)vol 37 no 1 pp 24ndash32 2017

[22] J B Hao X MWei J Yao et al ldquoStrength characteristics andmesostructure of wheat straw einforced soilrdquo Journal of TongjiUniversity (Natural Science) vol 47 no 6 pp 764ndash831 2019

[23] GB50007-2011 Code for Design of Building foundationMinistry of Housing and Urban-Rural Development BeijingChina 2012

[24] JTG D30-2015 Specifications for Design of Highway Sub-grades China Communications Publishing amp Media Man-agement Co Ltd Beijing China 2016

[25] GBT 50123-1999 Standard for Soil Test Method Ministry ofConstruction Beijing China 2000

14 Advances in Materials Science and Engineering

strength tests have been conducted on specimensmixed withwheat straw and cement -erefore investigations should becarried out further through other strength tests like directshear tests triaxial shear tests and so forth to study theinfluence of wheat straw on strength of specimens

Data Availability

-e data used to support the findings of this study are in-cluded within the article

Conflicts of Interest

-e authors declare no conflicts of interest with respect tothe research authorship andor publication of this article

Acknowledgments

-is work was financially supported by National NaturalScience Foundation of China (Grant no 51908430) Doc-toral Scientific Fund Project of Weifang University (Grantno 2017BS14) and Science and Technology Project of High-Tech Zone in Weifang (Grant no 2019KJHM09)

References

[1] R L Michalowski and J Cermak ldquoTriaxial compression ofsand reinforced with fibersrdquo Journal of Geotechnical andGeoenvironmental Engineering vol 129 no 2 pp 125ndash1362003

[2] T Yetimoglu M Inanir and O Esatinanir ldquoA study onbearing capacity of randomly distributed fiber-reinforcedsand fills overlying soft clayrdquo Geotextiles and Geomembranesvol 23 no 2 pp 174ndash183 2005

[3] T Park and S Tan ldquoEnhanced performance of reinforced soilwalls by the inclusion of short fiberrdquo Geotextiles and Geo-membranes vol 23 no 4 pp 348ndash361 2005

[4] C Tang B Shi W Gao F Chen and Y Cai ldquoStrength andmechanical behavior of short polypropylene fiber reinforcedand cement stabilized clayey soilrdquo Geotextiles and Geo-membranes vol 25 no 3 pp 194ndash202 2007

[5] S Salah N Shadi and F Fadi ldquoShear strength of fiber-reinforced sandsrdquo Journal of Geotechnical and Geo-environmental Engineering vol 136 no 3 pp 490ndash499 2010

[6] G A Santiago C Franco N C Consoli and V R BotaroldquoStudy of mechanical behavior of a sand soil reinforced withcuraua treated fibers with asphaltrdquo Materials Science Forumvol 730-732 pp 319ndash324 2012

[7] J Prabakar and R S Sridhar ldquoEffect of random inclusion ofsisal fibre on strength behaviour of soilrdquo Construction andBuilding Materials vol 16 no 2 pp 123ndash131 2002

[8] C Mahipal Singh M Satyendra and M BijayanandaldquoPerformance evaluation of silty sand subgrade reinforcedwith fly ash and fibrerdquoGeotextiles and Geomembranes vol 26no 5 pp 429ndash435 2008

[9] M Bouhicha F Aouissi and S Kenai ldquoPerformance ofcomposite soil reinforced with barley strawrdquo Cement andConcrete Composites vol 27 no 5 pp 617ndash621 2005

[10] N C Consoli M D T Casagrande P D M Prietto andA n -ome ldquoPlate load test on fiber-reinforced soilrdquo Journalof Geotechnical and Geoenvironmental Engineering vol 129no 10 pp 951ndash955 2003

[11] J Yao Experimental Study on Strength Characteristics ofWheat Straw Reinforced soil Changrsquoan University XirsquoanChina 2017

[12] A Adili A Rafig S Giovanni et al ldquoStrength of soil rein-forced with fiber materials (papyrus)rdquo Soil Mechanics andFoundation Engineering vol 48 no 6 pp 241ndash247 2012

[13] Y L Qian ldquoExperimentresearch of mechanical properties ofimproved saline soilrdquo Geotechnical Investigation and Sur-veying vol 5 pp 1ndash4 2003

[14] X S Wang H Q Zhang and M Xue ldquoRoad disease andtreatment in saline soil areardquo Journal of Tongji Universityvol 31 no 10 pp 1178ndash1182 2003

[15] Q LWang Y Chao Y F Liu et al ldquoMechanical properties ofsaline soil under the influence of different factorsrdquo FreseniusEnvironmental Bulletin vol 28 no 2A pp 1366ndash1373 2019

[16] L Wei S X Chai H Z Cai et al ldquoResearch on tensility ofwheat straw for reinforced materialrdquo Rock amp Soil Mechanicsvol 31 no 1 pp 128ndash132 2010

[17] L Wei S X Chai H Z Cai et al ldquoPhysical and mechanicalproperties of wheat straw and unconfined compressivestrength of reinforced inshore saline soil with wheat strawrdquoChina Civil Engineering Journal vol 43 no 3 pp 93ndash982010

[18] M Li S X Chai H P Du et al ldquoReasonable reinforcementposition and shear strength model of reinforced saline soilwith wheat straw and limerdquo Chinese Jourhal of Rock Me-chanics and Engineering vol 29 no sup 2 pp 3923ndash39292010

[19] P Wang S X Chai X Y Wang et al ldquoAnalysis of effectfactors of heavy compaction test for wheat straw-reinforcedsaline soilrdquo Rock and Soil Mechanics vol 32 no 2pp 448ndash452 2011

[20] L Wei S X Chai H Z Cai et al ldquoTriaxial shear strength anddeviatoric stress-strain of saline soils reinforced with wheatstrawsrdquo China Civil Engineering Journal vol 45 no 1pp 109ndash114 2012

[21] H Lu C G Yan X H Yang et al ldquoExperiment on anti-eroding property of reinforced loess with wheat strawrdquoJournal of Changrsquoan University (Natural Science Edition)vol 37 no 1 pp 24ndash32 2017

[22] J B Hao X MWei J Yao et al ldquoStrength characteristics andmesostructure of wheat straw einforced soilrdquo Journal of TongjiUniversity (Natural Science) vol 47 no 6 pp 764ndash831 2019

[23] GB50007-2011 Code for Design of Building foundationMinistry of Housing and Urban-Rural Development BeijingChina 2012

[24] JTG D30-2015 Specifications for Design of Highway Sub-grades China Communications Publishing amp Media Man-agement Co Ltd Beijing China 2016

[25] GBT 50123-1999 Standard for Soil Test Method Ministry ofConstruction Beijing China 2000

14 Advances in Materials Science and Engineering