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A N A LY S I S O F B E A R I N G C A P A C I T Y A N D S E T T L E M E N T O F J E T G R O U T I N G C O L U M N S

dardise the sounding parameters recorded to theform of coefficients and indicators used in the classi-fication systems and interpretation procedures.Soil types and states were determined based on pene-tration characteristics, supplemented with the curve offriction ratio Rfvs. depth. The classification systemdeveloped by the Department of Geotechnics ofAgricultural Academy in Pozna in 1993 and theRobertson system were used in the penetration curvesinterpretation. 8-step Harder-Bloh procedure wasused in the statistical analysis of penetration curves,

acc. to which sounding parameters were subject to fil-tration and the penetration curves smoothed.The course of five sounding characteristics vs. depthwas analysed to determine boundaries of individuallayers in the profile examined and to determine thetype and state of soils making those layers: cone resis-tance qn, friction on the frictional sleeve fs, porewater pressure uc and previously defined frictionratio Rfand pore pressure parameter Bq.

To separate uniform soil layers in the subsoil the datawas grouped in two stages. The data grouped in thefirst stage included the adjusted cone resistance qtand the coefficient of friction Rf. The Harder-Blohprocedure, modified by a sequential test, was used inthe first stage, which allowed separating the layersacc. to statistic criteria and to localise them in theclassification system of the Department ofGeotechnics of Agricultural Academy in Pozna. Inthe second stage the grouping was carried out fordata transformed from the penetration characteris-

tics qcand fs to standardised parameters Qtand Rf(the Heghazi-Mayne procedure).Once the data was grouped, the groups position onthe Robertson diagram was checked, what allowedchecking the consistency of soils classification acc. togranulation with the system of the Department ofGeotechnics of Agricultural Academy in Pozna [9]and assessing the correctness of soil state parameterschanges and the oversonsolidation state variability.The grouping was carried out using the cluster theo-

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Table 2.

Specifications of jet grouting columns reinforcement parameters [3]

Number of jet grouting columnTested jet grouting column Anchored jet grouting column

P1, P2, P4 P3 K1 K9

Assumption for diameterof jet grouting column, m 0.6 0.6 0.6

Length of jet grouting column, m 7.0 7.0 11.5

Type of reinforcement HEB 240 none HEB 160

Grade of steel St3S - St3S

Characteristic parametersof reinforcement

(H-section)

A=106 cm2

m=83.2 kg/mIx=11260 cm4

Iy=3920 cm4

Wx=938 cm3

Wy=327 cm3

-

A=54.3 cm2

m=42.6 kg/mIx=2490 cm4

Iy=889 cm4

Wx=311 cm3

Wy=111 cm3

Denotations: A area of reinforcement, m mass, Ix, Iy moment of inertia for reinforcement, Wx, Wy sectional modulus

Table 3.

Characteristic of trial loading for jet grouting columns [3]

Number of jet

grouting column P1 P2 P3 P4

Stage I of tests:

Type of testDate of test

Load test Uplift test Load test Uplift test

11.06.2007 4.06.2007 13.06.2007 5.06.2007

Stage II of tests:

Type of testDate of test

Uplift test Load test Load test Load test

9.04.2008 29.04.2008 11.04.2008 17.04.2008

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ry methods, considering the task as uniaxial, alongthe path of subsoil penetration with the cone in theplace of sounding.Diagrams developed in the Department ofGeotechnics of Agricultural Academy in Pozna and

in Hebo company, Pozna, were used to determinethe degree of non-cohesive soils compaction. Thecurrent theoretical solutions and comprehensive doc-umentation material from sources quoted were con-sidered in them.Shear parameters of soil layers separated in the sub-soil were expressed in effective stresses (). Thoseparameters were determined based on average valuesof sounding parameters (Bq and Nm), using theSenneset method.The Lunne method was used to determine deforma-tion parameters, expressed by means of oedometer

primary modulus of compressibility Mo.Those relationships include correction coefficientsdetermined by the Department of Geotechnics ofAgricultural Academy in Pozna and Hebo PoznaLtd., which were obtained on the basis of extensivedocumentation material from CPTU and laboratorytests [9].Dilatometer tests were performed using an originalMarchetti equipment. The tests were carried out inaccordance with the Instruction of TC-16 ISSMGECommittee International Reference Test Procedurefor DMT Test [10].DMT tests were performed in immediate vicinity ofstatic sounding places. The penetration was carriedout to previously assumed depth, performing mea-surements of characteristic pressures in each profile,at every 20 cm increment of depth. Individual mea-surements were performed in accordance with theprocedure recommended by the US Department ofTransportation Instruction and guidelines for DMTtests prepared for TC 16 ISSMGE Committee.CPTU tests characteristics (Fig. 2) and in particularthe characteristics of cone resistance changes vs.depth and the excess pore pressure very well identifythe occurrence of interbedding in the subsoil as wellas zones of strengthening and weakening, which arecaused by the construction of jet grouting columns inthe subsoil.The formation of zones of strengthening and weak-ening is reflected in strength and deformation para-meters of individual soil layers.The analysis carried out clearly shows that the zonesof strengthening and weakening exist on large depths

and the range of compaction degree variability inthose zones is pretty wide from 0.35 to 0.90. Similarsituation exists for the variability range of effectiveangle of internal friction and of modulus of primarycompressibility.

In a general assessment of strength and deformationparameters variability for individual soil layers of thesubsoil based on penetration characteristics fromCPTU, DMT and SDMT tests the following observa-tions may be formulated: The occurrence of soil layers of diversified stiff-

ness and strength has been found at each stage oftests. The spatial variability of those layers loca-tion is high. If characteristics from the SDMT testsare taken as the reference state, then it may benoticed that these zones only partially coincidewith zones documented by characteristics of

CPTU tests in individual test stages. Two factorsdecide about these differences, i.e. the differentia-tion of subsoil vertical and horizontal stiffness,which results from numerous soil layers interbed-ded in the subsoil, featuring various granulationand stiffness, and also effects related to the con-struction of jet grouting columns and their trialloading.

The characteristic of excess pore pressure changesat its simultaneous hydrostatic distribution withthe depth has shown that during individual stagesthe excess pore pressure was dispersing with time.

The subsoil tests in the test site in Bojszowy Nowe,carried out using CPTU, DMT and SDMT methodsfor two years, provided extensive material fordetailed interpretation of soil strength and deforma-tion parameters changes in the subsoil. Two aspectshave been considered when assessing these changes:the effect of jet grouting columns construction andthe trial loading. The passage of time of stage II andIII tests should be also considered. The limitation tothe three mentioned factors is possible, because char-acteristics from three test stages have shown that inthe examined time range the tests were always per-formed in the subsoil, which structure and spatialarrangement had not changed.The test results allowed carrying out detailed analy-sis, in which the aforementioned aspects have beenconsidered: When comparing the characteristics of horizontal

stress coefficient and secant dilatometer moduluschanges with the depth (Fig. 4 and Fig. 5) withchanges of secant oedometer moduli, obtainedfrom the CPTU tests, it is possible to state that the

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variability of these parameters is high. This com-parison allows assessing the anisotropy of individ-ual subsoil layers. The comparative analysis wasperformed in the subsoil zones, which had shownthe effect of strengthening and/or weakening. In

each stage those zones may be identified based onthe analysis of characteristics of cone resistancechanges with the depth, i.e. based on static CPTUtests.

When comparing the values of selected geotechni-cal parameters of the subsoil, determined based onpenetration characteristics in time intervals, i.e.before the construction of jet grouting columns inthe subsoil, after their construction and after aseries of trial loading of the columns, it is possibleto state that no significant difference in the valuesof effective angle of internal friction has beenfound in time intervals, while the most sensitiveparameter is the oedometer modulus of primarycompressibility, whose values determined afteruplift and load trial loading were substantiallydecreased. At the same time it has been noticedthat the construction of jet grouting columns andthen the performance of trial loading of jet grout-ing columns results in an increase (after columnsload trial loading) or in a decrease (after uplifttrial loading) in cone resistances during the CPTUtest.

Some difficulties are encountered at the definingof jet grouting columns interaction with the sub-soil, resulting from the fact that individual jetgrouting columns were subjected to two stages oftrial loading: loading and uplifting (reinforced jet grouting col-umn P1), uplifting and loading (reinforced jet groutingcolumns P2 and P4), loading twice (non-reinforced jet grouting col-umn P3).The soil surrounded by tested jet grouting columnswas changed after each series of their trial loading.

The soil structure in the zone immediately adja-cent to the column was disturbed (partly or totallydamaged). It should be emphasised that with timethe disturbed structure of the soil immediatelyadjacent to tested columns (uplifted or loaded)recovers.

Results of examinations of coefficient of frictionRfchanges vs. depth in the vicinity of jet groutingcolumns, subject to uplift trial loading and then toload trial loading (jet grouting column P2 and P4)

show that values of coefficient Rfdiminish. The Rfdetermined from tests in the vicinity of jet groutingcolumn P1, first subject to load trial loading andthen uplifted, has definitely higher values. Thehighest values of coefficient of friction occur in

CPTU-1bis test, in the vicinity of non-reinforcedjet grouting column P3, which was twice load trialloaded. Thereby in the vicinity of this column it ismost noticed that the excess pore pressure hasbeen dispersed.

When comparing selected values of parametersdetermined based on DMT and SDMT tests it maybe stated that the nature of penetration curves iscomparable, while some discrepancies result fromthe fact that the distance between DMT andSDMT test points was around 12.5 m. The best fitof compared curves along the jet grouting column

(l=7.0 m) occurs for material coefficient ID andchanges with depth of secant (oedometer) modu-lus of compressibility M.

The analysis of modulus of primary compressibili-ty values changes vs. vertical stresses, determinedin the vicinity of jet grouting columns P1P4,shows that in stage II of tests (after jet groutingcolumns construction in the subsoil) the M0valuesdecrease, while in stage III of tests (after trial load-ing of jet grouting columns) the M0 valuesincrease. That means that during columns uplift orload work the subsoils stiffness increases.

When comparing values of parameters determinedbased on dilatometer tests, performed in the vicin-ity of reinforced jet grouting column P2, it hasbeen found that values of horizontal stresses coef-ficient KD, of material coefficient ID and ofdilatometer modulus EDdecrease in the next teststages. The values of secant oedometer modulus,determined acc. to the Marchetti formula, also godown in the next test stages. When comparing val-ues of M0(from the CPTU test) with values of M(acc. to the Marchetti formula from the DMTtest), determined in the vicinity of reinforced jet

grouting column P2, it has been found that thesecant oedometer modulus M is around 23 timeshigher than the modulus of primary compressibili-ty M0. This proves an increase in the subsoil stiff-ness after the construction of jet grouting columnsas well as after columns load and uplift testing.

Results of stage III tests inform of possiblechanges in parameters of the subsoil and jet grout-ing column contact layer after the application ofexternal loads.

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Figure 2.

Specification of the CPTU tests results at the CPTU-1a, CPTU-1a and CPTU-1a bis tests at the neighbourhood of reinforced jet grout-

ing column P1 [6][8]

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3. AXIAL LOADING RESULTS

The trial loading of four jet grouting columns P1P4,constructed on the test site in Bojszowy Nowe, wasdesigned ([1][5]). The test jet grouting columnswere arranged in a square grid of 5.0 x 5.0 m dimen-sions (cf. Fig. 1). The design anticipated uplift andload trial loading of reinforced and non-reinforcedjet grouting columns. Tests were carried out in twostages: stage I comprised two uplift tests of reinforced jet

grouting columns P2 and P4 and two load tests: ofreinforced jet grouting column P1 and of non-rein-forced column P3,

stage II of tests carried out 10 months after stageI comprised three load tests of jet groutingcolumns P2, P3 and P4 and one uplift test of rein-forced jet grouting column P1.

The tests performed aimed at obtaining an answer tothe question, what part of the force is transferred tothe subsoil by the jet grouting column shaft and whatpart by the base during test columns uplifting andloading.

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Figure 3.

Changes in pressures of p0, p1 and p2 with the depth in the

DMT and SDMT tests [6][8]

Figure 4.

Indexes characterising DMT and SDMT tests [6][8]

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The value of maximum jet grouting column loading,adopted for calculations of resistance frame structureelements, amounted to 4000 kN, while for trial pullout load to 1200 kN.

Hydraulic actuators of lifting capacity up to 5000 kNtogether with accessories consisting of hydraulichoses and a pump with manometers were used in thetests.The main beam transverse beams system wasadapted to the anchoring columns and the loaded jetgrouting column location so as to obtain equalisedvalues of uplifting forces acting on individual anchor-ing columns [5]. Figure 6 presents the test stands forload and uplift tests of jet grouting columns.

4. ANALYSIS OF AXIAL TRIAL LOADS

4.1. Analysis of stage I tests

The following conclusions may be drawn based onthe results of analysis of uplift and load trial loading:

1) the share of jet grouting column base in transfer-ring the load is substantial and amounts to4855% of total jet grouting column bearingcapacity (compare Fig. 7),

2) the uplift bearing capacity of reinforced jet grout-ing columns tested (P2 and P4) amounts toNw=Nshaft11001200 kN= 1150 kN,

3) the load bearing capacity of reinforced jet groutingcolumn P1 amounts to Nt=25002600 kN=2550 kN; taking into account results for reinforcedjet grouting columns P2 and P4 subject to upliftingtests and their bearing capacity Nshaft=1150 kN, itmay be concluded that the bearing capacity ofreinforced jet grouting column base amounts toNbase=NtNw=25501150=1400 kN, henceNbase/Nshaft= 1400/1150=1.22,

4) from the comparison of load bearing capacity ofjet grouting columns: non-reinforced P3 and rein-forced P1 it results that there is no significant dif-ference between a non-reinforced and reinforcedcolumn in the load range between 0 and 2000 kN.


Figure 5.

Changes in compressibility modulus M with the depth on the

basis of Marchetti theory for DMT and SDMT tests [6][8]

Figure 6.

Test stand for jet grouting reinforced column a) load test;

b) uplift test

a

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4.2. Analysis of stage II tests

The following conclusions may be drawn analysingthe results of jet grouting columns uplift and loadtrial loading:

1) the conclusion of test stage I has been confirmed,i.e. that the share of column base in load transfer-ring to the subsoil is significant and amounts to5861% of jet grouting column total bearingcapacity (Fig. 8),

2) the uplift bearing capacity of reinforced jet grout-

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Figure 7.

Comparison of load-displacement relations for uplift tests of jet grouting columns P2 and P4 and load test of jet grouting column

P1 and P3

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Figure 8.

Test results for reinforced and non-reinforced jet grouting columns at stage II of tests

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ing column P1 amounts to Nw=Nshaft12001300 kN=1250 kN,

3) the load bearing capacity of reinforced jet groutingcolumns P2 and P4 amounts to Nt3200 kN; takinginto account results for reinforced jet grouting col-

umn P1, uplift tested, in particular its bearing capacityNshaft=1250 kN, the bearing capacity of jet groutingcolumns base Nbase=NtNw=32001250=1950 kNmay be determined, hence Nbase/Nshaft= 1950/1250==1.56,

4) from the comparison of jet grouting columns loadbearing capacity: non-reinforced P3 and reinforcedP2 and P4 (Fig. 8) it results that Nt(P3)=3000 kN,Nt(P2)=3200 kN, Nt(P4)=28003000 kN, so thereis no significant difference in load bearing capacityof reinforced and non-reinforced column

Nt(P2)/Nt(P3) = 3200/3000=1.07; Nt(P4)/Nt(P3) == 3000/3000 =1.00.

4.3. Analysis of stage I and II tests

Taking into account results of uplift and load trialloading, performed in stage I and II, the followingconclusions may be formulated:1) the nature of load cap displacement curves for

reinforced jet grouting columns P2 and P4, testedfor uplifting in stage I, is similar(Nw=11001200 kN1150 kN), but the course of

similar relationship for column P1 loaded in stageI is slightly different, the bearing capacity Nw, how-ever, achieves similar value of 1200 kN,

2) for reinforced jet grouting column P1, subject toload trial loading in stage I and to uplift trial load-

ing in stage II Nt=3200 kN, for reinforced jetgrouting columns P2 and P4, uplifted in stage I andloaded in stage II of the tests, Nt=30003200 kN,i.e. it is slightly smaller than for the column, whichis loaded in stage I,

3) when analysing results of tests for reinforced jetgrouting column P1 subject first to load trial load-ing and then to uplifting, the following wereobtained: Nt=3200 kN, Nw=Nshaft=12001300 kN 1250 kN, hence Nbase=3200-1250=1950 kN(compare Fig. 9),

4) when analysing results of tests for reinforced jetgrouting column P2 subject first to uplift trial load-ing and then to load, the following were obtained:Nt=3200 kN, Nw=Nshaft=1100 kN, henceNbase=3200-1100=2100 kN (compare Fig. 10),

5) for non-reinforced jet grouting column P3, subjectto load trial loading in stage I and II of tests (com-pare Fig. 11), the following results of tests wereobtained: from stage I NtI(P3)=23002400kN2350 kN, from stage II NtII(P3)=3200 kN,which means a significant increase in non-rein-forced jet grouting column bearing capacity in


Figure 9.

Test results for jet grouting reinforced column P1 stage I & II of tests

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stage II of loading NtII(P3)/NtI(P3) = 3200/2350== 1.36,

6) when analysing results of tests for reinforced jetgrouting column P4 subject first to uplift trial load-ing and then to load, the following were obtained:Nt=2800 kN, Nw=Nshaft=1200 kN, hence

Nbase=2800-1200=1600 kN (compare Fig. 12),

7) taking into consideration the fact that the rein-forced jet grouting columns P2 and P4 tests werecarried out in the same way, i.e. in stage I the rein-forced jet grouting columns P2 and P4 were uplift-ed and in stage II loaded, the two tests could be

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Figure 10.


Figure 11.Test results for jet grouting non-reinforced column P3 stage I & II of tests

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combined and average values of the bearing capac-ity determined: Ntaverage=(2800+3200)/2=3000 kN,Nw average=(1100+1200)/2=1150 kN, henceNbaseaverage=Ntaverage-Nw average= 3000-1150=1850 kN,

8) from the comparison of test results of reinforcedjet grouting columns P1 as well as P2 and P4 it

results that Nt(P1)=3200 kN, Nw

(P1)=1250 kN,Nt(P2 & P4)=3000 kN, Nw(P2 & P4)=1150 kN.

The comparative analysis shows that the operationof jet grouting columns first loaded and thenuplifted is slightly better.

5. SOIL-CEMENT MATERIAL TESTING

The tests of mechanical behaviour of soil-cementmaterial from the jet grouting columns in conditionsof uniaxial compression were carried out in the labo-

ratory on samples from the core material (Fig. 13),obtained from holes drilled in the column on the testsite. Before starting tests on the jet grouting columnmaterial, electric resistance strain gauges were gluedon the specimens to measure deformations. Theaverage value of soil-cement material uniaxial com-pressive strength Rc amounted to 21.122 MPa.The triaxial compression tests of soil-cement materi-al samples were carried out in a triaxial KTK-60 high-pressure cell using a hydraulic SHM-MG 250/4 test-

ing machine used for static and dynamic tests con-trolled by the force signal. The tests were carried outfor the lateral pressure ranging from 0.4 to 2.0 MPa.


Figure 12.


Figure 13.

a) View of shaft of jet grouting non-reinforced column P3

(l=7.0 m; head of jet grouting column D=1.6 m; below:

D=0.81.0 m; b) Samples of jet grouting material before

uniaxial and triaxial tests

a

b

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Based on stress-strain characteristics the values ofmodulus of elasticity Ei and the Poissons ratio i havebeen estimated. Average values of these parametersamount to E=9.888 GPa and =0.186.The values of the angle of internal friction , cohe-

sion c and their standard errors are as follows:=59.317, s=4.395, c=1.772 MPa, sc=0.858 MPa.

6. CONCLUSIONS

The conclusions presented have been drawn onlybased on the analysis of trial loading results for fourjet grouting columns in the test site in BojszowyNowe (Poland). The tests comprised the combinationof three reinforced columns and one non-reinforcedcolumn. A multi-option load programme has beenimplemented, comprising performance of reinforced

columns loading and uplifting in different order aswell as two-stage loading of non-reinforced column.This allowed estimating the shares in transferring thebase and shaft loads and also assessing the loadingpath influence on columns bearing capacity.

REFERENCES

[1] Bzwka J.; Experimental research of jet groutingcolumns, Inynieria i Budownictwo, 2010, No.5-6,p.292-295 (in Polish)

[2] Bzwka J.; FEM analysis of interaction of jet groutingcolumn with subsoil, Scientific Conference onNatural and Technical Problems of EnvironmentalEngineering Soil parameters from in situ and labo-ratory tests, Pozna 27-29 September 2010; p.445-455

[3] Bzwka J.; Interaction of jet grouting columns withsubsoil, Monograph, Silesian University ofTechnology Publishers, Gliwice 2009 (in Polish)

[4] Bzwka J., Pieczyrak J.; Pull out and load tests for jetgrouting columns, Proc. of the 11th Baltic SeaGeotechnical Conference, 15-18 September 2008,Gdask, Vol.2

[5] Excerpt from Static-Strength Calculations of theDesign for Jet Grouting Columns Trial Loading,Research Project No 4 T07E015 29, prepared by:G. aba, Bielsko-Biaa, April 2007 (in Polish)

[6] Geotechnical Parameters of Subsoil Soils on the TestSite in Bojszowy determined by means of the Methodof CPTU Static Sounding, Report No 314/06, HeboPozna Sp. z o.o., Pozna, October 2006 (in Polish)

[7] Geotechnical Parameters of Subsoil Soils in the TestSite in Bojszowy determined by means of the Methodof CPTU Static Sounding, Stage II ComparativeAnalysis, Report No 345/07, Hebo Pozna Sp. z o.o.,Pozna, September 2007 (in Polish)

[8] Geotechnical Parameters of Subsoil Soils in the TestSite in Bojszowy determined by means of the Methodof CPTU Static Sounding and the DMT and SDMTDilatometer Method, Stage III, Report No 380/08,Hebo Pozna Sp. z o.o., Pozna, October 2008 (inPolish)

[9] Guidelines on the Interpretation of PenetrationCharacteristics from the CPTU Method to Assess theSoil Type and Condition, including a Software forStatistical Analysis of Results of Tests using a StaticPenetrator, Department of Geotechnics of theAgricultural Academy in Pozna, 1993 (in Polish)

[10] International Reference Test Procedure for DMT-Test, Marchetti, 2003

[11] Modoni G., Bzwka J., Pieczyrak J.; Axial loading ofjet grouting columns, Proc. of the 14th Danube-European Conference on Geotechnical EngineeringFrom research to design in European Practice,Session 6: Numerical and physical models in geotech-

nical design, Bratislava, Slovak Republic, 2-4 June2010

[12] Modoni G., Bzwka J., Pieczyrak J.; Experimentalinvestigation and numerical modelling on the axialloading of jet grouting columns, Architecture, CivilEngineering, Environment Journal, 2010, Vol.3, No.3,p.69-78

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