applicability and accuracy of the initially dry and …...technical note applicability and accuracy...

TECHNICAL NOTE

Applicability and accuracy of the initially dry and initially wetcontact filter paper tests for matric suction measurement

of geosynthetic clay liners

A S ACIKEL R M SINGHdagger A BOUAZZA W P GATES and R K ROWEDagger

An initially wet contact filter paper test (IW-CFPT) and an initially dry contact filter paper test(ID-CFPT) were used to examine the wetting paths of geosynthetic clay liners including non-contactfilter paper tests for comparative purposes The CFPTs were applied to both geosynthetic clay linerfaces to examine the effect of geotextile type on capillary contact The non-woven geotextile face wasfound to be more likely to cause capillary breaks than the woven geotextile face Both IW- andID-CFPTs were found to be applicable to geosynthetic clay liners within their accurate upper matricsuction measurement limits of 146 kPa and 66 kPa respectively

KEYWORDS geosynthetics geotextiles laboratory tests suction time dependence

INTRODUCTIONThe primary function of bentonite within a geosynthetic clayliner (GCL) is to create impedance to the flow of migratingliquids dissolved chemical species and gases or vapours(Bouazza 2002 Rowe 2005) This is achieved by the verylow permeability of bentonite when fully hydrated after GCLplacement from the underlying or overlying soil (Gates et al2009 Bouazza amp Bowders 2010) When in service GCLs areoften subjected to variable hydration states during initialhydration and thermal cycling since they are typicallymanufactured at a low moisture content yet should behydrated to 100 moisture content to function adequatelyas a barrier to fluids and may be exposed to thermal cycles orelevated temperatures (Rowe amp Hoor 2009 Hornsey et al2010 Bouazza et al 2011 2013 2014) Hence under-standing the water retention behaviour of hydrating GCLs isessential to ensure their long-term longevity as hydraulicbarriers under adverse conditions

A limited number of studies have been carried out over thelast decade on the water retention behaviour of GCLs usingdifferent suction measurement techniques (Abuel-Naga ampBouazza 2010 Beddoe et al 2010 2011 Bannour et al2014 Rouf et al 2014) Among these techniques the contactfilter paper test (CFPT) is attractive owing to its simplicityand accessibility but has been used with limited successprimarily related to the accuracy of the suction measure-ments (Barroso et al 2006 Acikel et al 2011) Therefore atest programme based on the use of initially wet and drycontact filter paper tests (IW-CFPT ID-CFPT) as well as anon-contact filter paper test (NCFPT) as a reference wasconducted to better adapt the filter paper technique to matricsuction measurement of GCLs IW-CFPT and ID-CFPTtests were performed to evaluate the effect of capillarycontact and hysteresis on matric suction measurements Test

times of 1 week and 4 weekswere used to investigate the effectof suction equilibrium time on matric suction by IW-CFPTStandard 1-week ID-CFPT and NCFPTs were conductedas reference tests All contact tests were applied to boththe non-woven cover andwoven carrier geotextile faces of theGCLs to investigate the impact of different geotextiles on thecapillary contact condition between GCL and filter paperFilter paper pore size distributions obtained from scanningelectron microscopy (SEM) imaging provided a sound basisfor discussing the results

BackgroundMost filter paper calibration curves (Fawcett amp

Collis-George 1967 Greacen et al 1987 Chandler et al1992a 1992b Crilly amp Chandler 1993 Leong et al 2002ASTM 2010) follow a piecewise defined function consideredto be a composite of two functions with a break point at theirintersection Table 1 shows the gravimetric water content offilter papers and corresponding suction values at the breakpoints of the most common filter paper calibration equationsrecommended for Whatman no 42 filter paperThewetting solidndashliquid contact angles of solidndashliquidndashgas

interfaces are considerably larger than their respective dryingcontact angles resulting in contact angle hysteresis (Lu ampLikos 2004) Liukkonen (1997) investigated the wettingproperties of paper components by measuring the contactangles of water drops on sample surfaces and by observingmicroscopic drops in an environmental scanning electronmicroscope (ESEM) Liukkonen (1997) reported that holo-cellulose and α-cellulose components of dry paper hadinitial contact angles of respectively 56deg and 26deg but bothdecreased to 0deg with wetting A contact angle equal to 0 isdescribed as a perfectly wetting material (Lu amp Likos 2004)or hydrophilic material in the context of geotextiles(Bouazza 2014)Lu amp Likos (2004) and Fredlund (2006) described the

different saturation zones of a typical water retention curve(WRC) as the boundary effect (capillary fringe) zonetransition (capillary) zone and residual (pendular) zoneWater transfer within the boundary effect zone can occur inthe liquid phase while in the transition zone it can be both

Monash University Melbourne Australiadagger University of Surrey Guildford Surrey UKDagger Queenrsquos University Kingston Canada

Manuscript received 12 December 2013 revised manuscriptaccepted 19May 2015 Published online ahead of print 13 July 2015Discussion on this paper closes on 1 February 2016 for furtherdetails see p ii

Acikel A S et al (2015) Geacuteotechnique 65 No 9 780ndash787 [httpdxdoiorg101680geot13P222]

780

Downloaded by [ UNIVERSITY OF SURREY] on [290716] Copyright copy ICE Publishing all rights reserved

liquid and vapour phase but transfer in the residual zone canonly be in the vapour phase Liquid water transfer relies onconnected capillarity whereas vapour transfer relies on openporesThe lsquoentryrsquoor lsquobubblingrsquopressure of porousmedia is the thre-

shold pressure for displacement between wetting and non-wetting fluids (Bear 1972) In the wetting and drying pathsunder study the airentryvalueof a drying curve is the thresholdpressure where water is initially replaced by air Likewise thewater entry value of awetting curve is the threshold pressure atwhich air is initially replaced by water (Wang et al 2000) Thesuction value between transition and residual zones on thedrying curve is defined by residual pressure

MATERIALS AND METHODOLOGYMaterialsWhatman no 42 filter papers and a granular bentonite

based GCL were used The needle-punched GCL (Table 2)was composed of a layer of bentonite sandwiched between awoven carrier and a non-woven cover geotextile with thesystem being held together by needle punching

MethodsFilter paper test Geosynthetic clay liner specimens werecut at off-roll water contents using a hydraulic press and asharp stainless steel cutter The specimens were gluedinto polyvinyl chloride (PVC) rings (20 mm high 50 mminternal diameter) They were then hydrated using steriledistilled water to targeted gravimetric water contents Thehydrated specimens were sealed and stored at a constanttemperature of 22degC under a 1 kPa confining stress for 6weeks to reach hydration equilibrium throughout thespecimen The ID-CFPT IW-CFPTand NCFPT procedureswere performed on the homogenised specimens A strictsterilisation procedure (consisting of bleaching and ethanolflash-flaming the testing surfaces and tools and flamingthe surrounding air with a Bunsen burner as well as usingsterile disposable gloves and masks) was followed to mini-mise any microorganism growth in the system during thetests Sterile distilled water was used to hydrate the GCLspecimensFigure 1 shows the IW-CFPT procedure A stack of

three filter papers (50 mm protectorndash42middot5 mm sensorndash50 mm protector) were placed on both the cover andcarrier geotextile faces of the specimens The sensor filterpapers were soaked in sterile distilled water for 1 h beforebeing used for the IW-CFPT The only difference between theID-CFPT and IW-CFPT procedures was the initial gravi-metric water content condition of the inner (sensor) filterpaper which was placed between two dry outer (protector)filter papers In the ID-CFPT the sensor filter paper wasdry whereas in the IW-CFPT the sensor filter paper wassaturated A 1 kPa contact pressure was applied For theNCFPT capillary contact was not required and thereforethe filter papers (42 cm diameter and oven dried) wereused only on the non-woven geotextile side with O-ringseparators to prevent contact between GCL and dry

Table 1 Water content and corresponding suction values of the breakpoints of Whatman no 42 filter paper calibration equations

Watercontent

SuctionkPa

Calibration

45middot3 66middot3 ASTM D 5298 (ASTM 2010)45middot3 63middot1 Fawcett amp Collis-George (1967)45middot3 63middot3 Greacen et al (1987)47 80middot0 Chandler et al (1992a 1992b)47 82middot5 Crilly amp Chandler (1993)47 68middot0 Leong et al (2002)

Table 2 Technical properties of the GCL used in the present investigation

Mass per unit area g=m2

GCLMeasured 4698MARV 4000

BentoniteCalculated 4273MARV 3600

Carrier geotextileMeasured 126

Cover geotextileMeasured 299

BentoniteParticle type GranularMontmorillonite (XRD test results)dagger 82Initial (off-roll) gravimetric water content 12Liquid limit (ASTM D 4318 (ASTM 2000)) 370Plastic limit (ASTM D 4318 (ASTM 2000)) 36Swell indexDagger ml=2 g (ASTM D 5890 (ASTM 2011)) 22Hydraulic conductivitysect m=s (ASTM D 5887 (ASTM 2009a)) 51011

StructureConfiguration (carrier=cover) W=NWBonding NPPeel strength N=m (ASTM D 6496 (ASTM 2009b))|| 1247Thermally treated No

MARV minimum average roll value (from producer) SRNW scrim-reinforced non-woven W woven NW non-woven NPneedle-puncheddaggerXRD tests conducted at CSIRO Land and Water Mineralogical Services Adelaide laboratoryDaggerTests were performed on the bentonite specimens extracted from GCLs Some inevitable remaining fibres might decrease the swell indexvaluessectMax values as provided by the manufacturers||Tests were performed by Geofabrics Australasia Geosynthetic Centre of Excellence Queensland

CONTACT FILTER PAPER TESTS FOR MATRIC SUCTION MEASUREMENT 781


protector filter papers (Fig 2) The specimens were thensealed and kept at a constant temperature of 22degC during thetests (1 and 4 weeks for IW-CFPT 1 week for ID-CFPT andNCFPT)

SEM analysis of Whatman no 42 filter paper The filterpapers were oven dried at 105degC overnight The oven-driedspecimens were coated with a very thin layer of iridiumto avoid charging during SEM imaging Then the pore

Fig 1 Initially wet contact filter paper test (IW-CFPT) procedures

Fig 2 Non-contact filter paper test (NCFPT) procedures

ACIKEL SINGH BOUAZZA GATES AND ROWE782


sizes were measured from six SEM images by hand Fig 3shows one of the SEM images where the pore sizes weremeasuredA distribution analysis was performed on the measured

pore size values Pore sizes larger than 8 μm were not takeninto consideration for pore size distribution analysis sincevery few pores exist at this range The counts of the pore sizesmeasured from SEM images were extrapolated for a 1 mm2

area Fig 4 shows a histogram for the pore size distributionof Whatman no 42 filter paper In the filter paper pore sizerange of 0middot5ndash8 μm the pores explicitly had a dominant size of2 μm

TEST RESULTS AND DISCUSSIONGeosythetic clay liner wetting path suction measurement

test results calculated using calibration equations rec-ommended by ASTM-D5298 (ASTM 2010) (Table 3) arepresented in Fig 5 The 1-week ID-CFPT and IW-CFPTgave comparable results for suction values ~70 kPahowever suction values of the ID-CFPT were significantly

higher compared to those of the IW-CFPT for the suctionrange 70 kPa The ID-CFPT results eventually mergedwith the NCFPTwith the increase of the suction values Forthe suction range 100 kPa the 4-week IW-CFPT gaveslightly smaller suction values than the 1-week test Thesuction results of CFPTobtained from the cover (non-woven)were greater than those obtained from the carrier (woven)geotextileThe wetting path matric suction results of CFPTs are

comparedwith wetting and drying path matric suction resultsreported by Beddoe et al (2011) for the same GCL usinga high-capacity tensiometer (HCT) in Fig 6 The results of4-week IW-CFPT applied on the carrier (woven) geotextileare highly comparable with the wetting path results of HCTCompared to the tensiometer results the ID-CFPT over-estimated the matric suction at values 70 kPaCapillary rise in an ideal cylindrical tube is defined by the

YoungndashLaplace equation which can be expressed as

Δp frac14 4γ cos θD

eth1THORN

where Δp is capillary pressure γ is surface tension θis contact angle and D is the average effective diameterof pores The surface tension of water at 22degC is 7middot2102 N=mThe contact angles reported by Liukkonen (1997) were

substituted in equation (1) to calculate capillary pressures ofWhatman no 42 filter paper for the particle retention valuesof the filter paper (2middot5 μm) reported by the manufacturer aswell as the peak pore size (2 μm) obtained from the SEMimages (Table 4)Different calibrations of Whatman no 42 for drying and

wetting paths (modified from Munoz-Castelblanco et al(2012)) drying=wetting path hysteresis as well as two breakpoints are shown in Fig 7(a) Fig 7(b) was generalised fromFig 7(a) as a conceptual WRCmodel for filter paper wettingand drying paths assuming filter paper had similar waterretention behaviour as soils According to this conceptual

Fibres

Pores

Fig 3 One of the SEM images of oven-dried Whatman no 42 filterpaper

0

2000

4000

6000

8000

10 000

12 000

14 000

0middot5 1middot0 1middot5 2middot0 2middot5 3middot0 3middot5 4middot0 4middot5 5middot0 5middot5 7middot0 7middot5

Freq

uenc

y in

1 m

m2

Pore size microm

Fig 4 Pore size distribution of Whatman no 42 filter paper as determined on pore lt8 μm diameter from SEM images (the pore size distributioncounts were extrapolated per mm2)

Table 3 Filter paper calibration equations recommended by ASTMD 5298 (ASTM 2010)

w45middot3 Log10(ψ)frac145middot327ndash0middot0779ww45middot3 Log10(ψ)frac142middot412ndash0middot0135w

w is the water content () and ψ is the suction (kPa) of filter paper



model the drying curve break point corresponds to residualpressure (the inflection point between residual and transitionzones) of the drying path WRC and similarly the wetting

curve break point corresponds to the water entry value ofwetting path WRC The break point of the drying (initiallywet) and wetting (initially dry) curves (Fig 7(a)) correspond

0

20

40

60

80

100

120

140

160

180

200

1 10 100 1000 10 000 100 000 1 000 000

Gra

vim

etric

wat

er c

onte

nt

Suction kPa

1-week IW-CFPT cover

1-week IW-CFPT carrier



1-week ID-CFPT cover

1-week ID-CFPT carrier

1-week NCFPT

Fig 5 One- and 4-week initially wet contact as well as 1-week initially dry contact and non-contact filter paper test results of the GCL wettingpath

0

20

40

60

80

100

120

140

160

180

200

1 10 100 1000 10 000 100 000

Gra

vim

etric

wat

er c

onte

nt

Suction kPa







HCT by Beddoe et al (2011)

Fig 6 Comparison of wetting path suction measurements of 1-week and 4-week initially wet contact filter paper tests as well as 1-week initiallydry contact filter paper tests with measurements of HCT by Beddoe et al (2011) for the wetting path of the same GCL type



146 kPa 48

66 kPa 45

0

20

40

60

80

100

120

140

160

180

0middot1 1middot0 10middot0 100middot0 1000middot0 10 000middot0 1 00 000middot0 10 00 000middot0

Wat

er c

onte

nt

Suction kPa

(a)

(b)

Ridley (1995) dryingRidley (1995) wettingHarrison amp Blight (1998) dryingHarrison amp Blight (1998) wettingLeong et al (2002) dryingLeong et al (2002) wettingParcevaux (1980) dryingFawcett amp Collis-George (1967) wettingHamblin (1981) wettingGreacen et al (1987) wettingWet filter paper (Parcevaux 1980)Dry filter paper (ASTM 2003)

Suction in logarithmic scale

Wat

er c

onte

nt

suction

value

Drying

Wetting

Capillary pressure by YoungndashLaplace equation

During water entry(θ = 56deg D = 2middot5 mm) (θ = 0deg D = 2middot0 mm)

After water entry

65 kPa 144 kPa

Residual

Water entry

Fig 7 (a) Calibration curves for Whatman no 42 filter paper (modified from Munoz-Castelblanco et al (2012)) (the two larger circles show thebreak points) (b) Conceptual model of filter paper water retention behaviour and hysteresis between wetting and drying paths

Table 4 Capillary pressure values calculated using the YoungndashLaplace equation (equation (1)) for possible filter paper pore sizes and contactangles

Capillary pressure kPa Contact angles degrees

0 26 56

Pore size μm2 144 130 812middot5 116 104 65



approximately to suctions of 146 kPa (wfrac1448) and 66 kPa(wfrac1445) respectively The YoungndashLaplace equation gives144 kPa (Table 4) for the wet case (θfrac140deg Dfrac142middot0 μm) whichis very close to the suction value at the break point of theinitially wet calibration curve 146 kPa The suction values atthe break points presented in Table 1 (63middot1ndash82middot5 kPa)correspond to the calculated capillary pressure values of65 kPa and 81 kPa for a dry contact angle of 56deg (Table 3)The wetting path (initially dry) break point in Fig 7(a) alsocorresponds to the calculated capillary pressure for aninitially dry contact angle of 56deg and particle retentionvalue (2middot5 μm)

Since the CFPT requires capillary contact between GCLspecimen and filter paper the inflection point between theresidual-transition zones of the drying curve and the waterentry value of the wetting curve should give the accuratematric suction measurement limits of IW-CFPT andID-CFPT respectively The requirement of capillarycontact also explains why IW-CFPT and ID-CFPT gavecomparable results up to ~70 kPa which coincides with theaccurate measurement limit of ID-CFPT The suction resultsof both CFPTs have eventually merged with the NCFPTresults after the proposed limit values of 146 and 66 kPawerepassed

The contact test suction values from non-woven covergeotextile side (Figs 5 and 6) merged with the values ofNCFPT at lower suctions This result indicates that thenon-woven geotextile used had higher tendency to provide acapillary break than the woven geotextile

CONCLUSIONSInitially dry and wet contact filter paper test (ID-CFPT

and IW-CFPT) methodologies were found to be applicablefor GCL matric suction measurements The ID-CFPT (theASTM standard contact filter paper test) and IW-CFPTmethods had theoretical measurement limits of ~66 kPa and~146 kPa respectively based on measured pore size distri-butions of the filter paper used The 4-week IW-CFPTapplied to woven geotextile faces is recommended for matricsuction measurement using the filter paper method for GCLson the wetting path A non-woven geotextile was found to bemore likely to act as a capillary break than awoven geotextile

ACKNOWLEDGEMENTSThis research was supported through the Linkage Projects

funding scheme (project number LP 0989415) with govern-mental funding provided by the Austsralian ResearchCouncil and industry funding provided by GeofabricsAustralasia Pty Ltd The first author was partially fundedby Monash University The authors are grateful for thissupport

REFERENCESAbuel-Naga H M amp Bouazza A (2010) A novel laboratory

technique to determine the water retention curve of geosyntheticclay liners Geosynthetics Int 17 No 5 313ndash322

Acikel A S Singh R M Bouazza A Gates W P amp Rowe R K(2011) Water retention behaviour of unsaturated geosyntheticclay liners Proceedings of 13th international conference ofthe International Association for Computer Methods andAdvances in Geomechanics Melbourne Victoria Australiavol 2 pp 626ndash630

ASTM (2000) D 4318 Standard test methods for liquid limitplastic limit and plasticity index of soils West ConshohockenPA USA ASTM International

ASTM (2003) D 5298 Standard test method for measurement ofsoil potential (suction) using filter paper West ConshohockenPA USA ASTM International

ASTM (2009a) D 5887 Standard test method for measurement ofindex flux through saturated geosynthetic clay liner specimensusing a flexible wall permeameter West Conshohocken PAUSA ASTM International

ASTM (2009b) D 6496 Standard test method for determiningaverage bonding peel strength between the top and bottomlayers of needle-punched geosynthetic clay liners WestConshohocken PA USA ASTM International


ASTM (2011) D 5890 Standard test method for swell indexof clay mineral component of geosynthetic clay liners WestConshohocken PA USA ASTM International

Bannour H Stoltz G Delage P amp Touze-Foltz N (2014) Effectof stress on water retention of needlepunched geosynthetic clayliners Geotextiles Geomembranes 42 No 6 629ndash640

Barroso M Touze-Foltz N amp Saidi F K (2006) Validation of theuse of filter paper suction measurements for the determinationof GCL water retention curves Proceedings of the 8th inter-national conference on geosynthetics Yokohama Japan vol 2pp 171ndash174

Bear J (1972) Dynamics of fluids in porous media 2nd ednNew York NY USA Elsevier

Beddoe R A Take W A amp Rowe R K (2010) Development ofsuction measurement techniques to quantify the water retentionbehaviour of GCLs Geosynthetics Int 17 No 5 301ndash312

Beddoe R A Take W A amp Rowe R K (2011) Water-retentionbehavior of geosynthetic clay liners J Geotech Geoenv Engng137 No 11 1028ndash1038

Bouazza A (2002) Geosynthetic clay liners Geotextiles andGeomembranes 20 No 1 3ndash17

Bouazza A (2014) A simple method to assess the wettability ofnonwoven geotextiles Geotextiles Geomembranes 42 No 4417ndash419

Bouazza A amp Bowders J J (2010) Geosynthetic clay linersin waste containment facilities Rotterdam the NetherlandsCRC Press=Balkema

Bouazza A Nahlawi H amp Aylward M (2011) In situtemperature monitoring in an organic-waste landfill cellJ Geotech Geoenviron Engng 137 No 12 1286ndash1289

Bouazza A Zornberg J McCartney J amp Singh R M (2013)Unsaturated geotechnics applied to geoenvironmental engineer-ing problems involving geosyntheticsEngng Geol 165 143ndash153

Bouazza A Singh R M Rowe R K amp Gassner F (2014)Heat and moisture migration in a geomembranendashGCL com-posite liner subjected to high temperatures and low verticalstresses Geotextiles Geomembranes 42 No 5 555ndash563

Chandler R J Crilly M S amp Montgomery-Smith G (1992a) Alow-cost method of assessing clay desiccation for low-risebuildings Proc Inst Civil Engrs 92 No 2 82ndash89

Chandler R J Harwood A H amp Skinner P J (1992b) Sampledisturbance in London Clay Geacuteotechnique 42 No 4 577ndash585http==dxdoiorg=101680=geot1992424577

Crilly M S amp Chandler R J (1993) A method of determiningthe state of desiccation in clay soils Info Paper Bldg Res Est 4No 93 1ndash4

Fawcett R amp Collis-George N (1967) A filter-paper method fordetermining the moisture characteristics of soil Aust J ExplAgric 7 No 25 162ndash167

Fredlund D G (2006) Unsaturated soil mechanics in engineeringpractice J Geotech Geoenviron Engng 132 No 3 286ndash321

Gates W P Bouazza A amp Churchman G J (2009) Bentonite claykeeps pollutants at bay Elements 5 No 2 105ndash110

Greacen E L Walker G R amp Cook P G (1987) Evaluationof the filter paper method for measuring soil water suctionProceedings of the international conference on measurement ofsoil and plant water status Logan UT USA pp 137ndash143

Hamblin A P (1981) Filter-paper method for routine measure-ment of field water potential J Hydrol 53 No 3ndash4 355ndash360

Harrison B A amp Blight G E (1998) The effect of filter paper andpsychrometer calibration techniques on soil suction measure-ments Proceedings of the 2nd international conference onunsaturated soils Beijing China pp 362ndash367

Hornsey W P Scheirs J Gates W P amp Bouazza A (2010) Theimpact of mining solutions=liquors on geosyntheticsGeotextiles



Geomembranes 28 No 2 191ndash198 doi 101016=jgeotexmem200910008

Leong E C He L amp Rahardjo H (2002) Factors affecting thefilter paper method for total and matric suction measurementsGeotech Testing J 25 No 3 322ndash333

Liukkonen A (1997) Contact angle of water on paper componentsSessile drops versus environmental scanning electron microscopemeasurements Scanning 19 No 6 411ndash415

Lu N amp Likos W J (2004) Unsaturated soil mechanics New YorkNY USA John Wiley

Munoz-Castelblanco J A Pereira J M Delage P amp Cui Y J(2012) The water retention properties of a natural unsaturatedloess from northern France Geacuteotechnique 62 No 2 95ndash106http==dxdoiorg=101680=geot9P084

Parcevaux P (1980) Etude microscopique et macroscopiquedu gonflement de sols argileux PhD thesis Ecole NationaleSupeacuterieure des Mines de Paris Paris France (in French)

Ridley A M (1995) Discussion on lsquoLaboratory filter papersuction measurementsrsquo by S L Houston W N Houston andA M Wagner Geotech Testing J 18 No 3 391ndash396

Rouf M A Singh R M Bouazza A Gates W P amp Rowe R K(2014) Evaluation of a geosynthetic clay liner water retentioncurve using vapour equilibrium technique Proceedings of the6th international conference on unsaturated soils UNSAT 2014Sydney NSW Australia vol 2 pp 1003ndash1009

Rowe R K (2005) Long-term performance of contaminantbarrier systems Geacuteotechnique 55 No 9 631ndash678 http==dxdoiorg=101680=geot2005559631

Rowe R K amp Hoor A (2009) Predicted temperatures and servicelives of secondary geomembrane landfill liners GeosyntheticsInt 16 No 2 71ndash82

Wang Z Wu L amp Wu Q J (2000) Water-entry value as analternative indicator of soil water-repellency and wettabilityJ Hydrol 231ndash232 76ndash83



Table 1

Table 2

Figure 1

Figure 2

Figure 3

Figure 4

Table 3

Figure 5

Figure 6

Figure 7

Table 4

Reference 1

Reference 2

Reference 3

Reference 3a

Reference 4

Reference 3b

Reference 5

Reference 6

Reference 7

Reference 8

Reference 9

Reference 10

Reference 10a

Reference 11

Reference 12

Reference 13

Reference 14

Reference 15

Reference 16

Reference 18

Reference 19

Reference 20

Reference 21

Reference 22

Reference 23

Reference 24

Reference 25

Reference 26

Reference 27

Reference 28

Reference 29

Reference 30

Reference 31

Reference 32

Reference 33

Reference 34

Reference 35

Reference 36

Reference 38

liquid and vapour phase but transfer in the residual zone canonly be in the vapour phase Liquid water transfer relies onconnected capillarity whereas vapour transfer relies on openporesThe lsquoentryrsquoor lsquobubblingrsquopressure of porousmedia is the thre-

shold pressure for displacement between wetting and non-wetting fluids (Bear 1972) In the wetting and drying pathsunder study the airentryvalueof a drying curve is the thresholdpressure where water is initially replaced by air Likewise thewater entry value of awetting curve is the threshold pressure atwhich air is initially replaced by water (Wang et al 2000) Thesuction value between transition and residual zones on thedrying curve is defined by residual pressure

MATERIALS AND METHODOLOGYMaterialsWhatman no 42 filter papers and a granular bentonite

based GCL were used The needle-punched GCL (Table 2)was composed of a layer of bentonite sandwiched between awoven carrier and a non-woven cover geotextile with thesystem being held together by needle punching

MethodsFilter paper test Geosynthetic clay liner specimens werecut at off-roll water contents using a hydraulic press and asharp stainless steel cutter The specimens were gluedinto polyvinyl chloride (PVC) rings (20 mm high 50 mminternal diameter) They were then hydrated using steriledistilled water to targeted gravimetric water contents Thehydrated specimens were sealed and stored at a constanttemperature of 22degC under a 1 kPa confining stress for 6weeks to reach hydration equilibrium throughout thespecimen The ID-CFPT IW-CFPTand NCFPT procedureswere performed on the homogenised specimens A strictsterilisation procedure (consisting of bleaching and ethanolflash-flaming the testing surfaces and tools and flamingthe surrounding air with a Bunsen burner as well as usingsterile disposable gloves and masks) was followed to mini-mise any microorganism growth in the system during thetests Sterile distilled water was used to hydrate the GCLspecimensFigure 1 shows the IW-CFPT procedure A stack of

three filter papers (50 mm protectorndash42middot5 mm sensorndash50 mm protector) were placed on both the cover andcarrier geotextile faces of the specimens The sensor filterpapers were soaked in sterile distilled water for 1 h beforebeing used for the IW-CFPT The only difference between theID-CFPT and IW-CFPT procedures was the initial gravi-metric water content condition of the inner (sensor) filterpaper which was placed between two dry outer (protector)filter papers In the ID-CFPT the sensor filter paper wasdry whereas in the IW-CFPT the sensor filter paper wassaturated A 1 kPa contact pressure was applied For theNCFPT capillary contact was not required and thereforethe filter papers (42 cm diameter and oven dried) wereused only on the non-woven geotextile side with O-ringseparators to prevent contact between GCL and dry

Table 1 Water content and corresponding suction values of the breakpoints of Whatman no 42 filter paper calibration equations

Watercontent

SuctionkPa

Calibration

45middot3 66middot3 ASTM D 5298 (ASTM 2010)45middot3 63middot1 Fawcett amp Collis-George (1967)45middot3 63middot3 Greacen et al (1987)47 80middot0 Chandler et al (1992a 1992b)47 82middot5 Crilly amp Chandler (1993)47 68middot0 Leong et al (2002)

Table 2 Technical properties of the GCL used in the present investigation

Mass per unit area g=m2

GCLMeasured 4698MARV 4000

BentoniteCalculated 4273MARV 3600

Carrier geotextileMeasured 126

Cover geotextileMeasured 299

BentoniteParticle type GranularMontmorillonite (XRD test results)dagger 82Initial (off-roll) gravimetric water content 12Liquid limit (ASTM D 4318 (ASTM 2000)) 370Plastic limit (ASTM D 4318 (ASTM 2000)) 36Swell indexDagger ml=2 g (ASTM D 5890 (ASTM 2011)) 22Hydraulic conductivitysect m=s (ASTM D 5887 (ASTM 2009a)) 51011

StructureConfiguration (carrier=cover) W=NWBonding NPPeel strength N=m (ASTM D 6496 (ASTM 2009b))|| 1247Thermally treated No

MARV minimum average roll value (from producer) SRNW scrim-reinforced non-woven W woven NW non-woven NPneedle-puncheddaggerXRD tests conducted at CSIRO Land and Water Mineralogical Services Adelaide laboratoryDaggerTests were performed on the bentonite specimens extracted from GCLs Some inevitable remaining fibres might decrease the swell indexvaluessectMax values as provided by the manufacturers||Tests were performed by Geofabrics Australasia Geosynthetic Centre of Excellence Queensland


















eth1THORN




Fibres

Pores


0

2000

4000

6000

8000

10 000

12 000

14 000


Freq

uenc

y in

1 m

m2

Pore size microm









0

20

40

60

80

100

120

140

160

180

200

1 10 100 1000 10 000 100 000 1 000 000

Gra

vim

etric

wat

er c

onte

nt

Suction kPa







1-week NCFPT


0

20

40

60

80

100

120

140

160

180

200

1 10 100 1000 10 000 100 000

Gra

vim

etric

wat

er c

onte

nt

Suction kPa











146 kPa 48

66 kPa 45

0

20

40

60

80

100

120

140

160

180


Wat

er c

onte

nt

Suction kPa

(a)

(b)



Wat

er c

onte

nt

suction

value

Drying

Wetting



After water entry

65 kPa 144 kPa

Residual

Water entry




0 26 56
























































Table 1

Table 2

Figure 1

Figure 2

Figure 3

Figure 4

Table 3

Figure 5

Figure 6

Figure 7

Table 4

Reference 1

Reference 2

Reference 3

Reference 3a

Reference 4

Reference 3b

Reference 5

Reference 6

Reference 7

Reference 8

Reference 9

Reference 10

Reference 10a

Reference 11

Reference 12

Reference 13

Reference 14

Reference 15

Reference 16

Reference 18

Reference 19

Reference 20

Reference 21

Reference 22

Reference 23

Reference 24

Reference 25

Reference 26

Reference 27

Reference 28

Reference 29

Reference 30

Reference 31

Reference 32

Reference 33

Reference 34

Reference 35

Reference 36

Reference 38
















eth1THORN




Fibres

Pores


0

2000

4000

6000

8000

10 000

12 000

14 000


Freq

uenc

y in

1 m

m2

Pore size microm









0

20

40

60

80

100

120

140

160

180

200

1 10 100 1000 10 000 100 000 1 000 000

Gra

vim

etric

wat

er c

onte

nt

Suction kPa







1-week NCFPT


0

20

40

60

80

100

120

140

160

180

200

1 10 100 1000 10 000 100 000

Gra

vim

etric

wat

er c

onte

nt

Suction kPa











146 kPa 48

66 kPa 45

0

20

40

60

80

100

120

140

160

180


Wat

er c

onte

nt

Suction kPa

(a)

(b)



Wat

er c

onte

nt

suction

value

Drying

Wetting



After water entry

65 kPa 144 kPa

Residual

Water entry




0 26 56
























































Table 1

Table 2

Figure 1

Figure 2

Figure 3

Figure 4

Table 3

Figure 5

Figure 6

Figure 7

Table 4

Reference 1

Reference 2

Reference 3

Reference 3a

Reference 4

Reference 3b

Reference 5

Reference 6

Reference 7

Reference 8

Reference 9

Reference 10

Reference 10a

Reference 11

Reference 12

Reference 13

Reference 14

Reference 15

Reference 16

Reference 18

Reference 19

Reference 20

Reference 21

Reference 22

Reference 23

Reference 24

Reference 25

Reference 26

Reference 27

Reference 28

Reference 29

Reference 30

Reference 31

Reference 32

Reference 33

Reference 34

Reference 35

Reference 36

Reference 38



0

20

40

60

80

100

120

140

160

180

200

1 10 100 1000 10 000 100 000 1 000 000

Gra

vim

etric

wat

er c

onte

nt

Suction kPa







1-week NCFPT


0

20

40

60

80

100

120

140

160

180

200

1 10 100 1000 10 000 100 000

Gra

vim

etric

wat

er c

onte

nt

Suction kPa











146 kPa 48

66 kPa 45

0

20

40

60

80

100

120

140

160

180


Wat

er c

onte

nt

Suction kPa

(a)

(b)



Wat

er c

onte

nt

suction

value

Drying

Wetting



After water entry

65 kPa 144 kPa

Residual

Water entry




0 26 56
























































Table 1

Table 2

Figure 1

Figure 2

Figure 3

Figure 4

Table 3

Figure 5

Figure 6

Figure 7

Table 4

Reference 1

Reference 2

Reference 3

Reference 3a

Reference 4

Reference 3b

Reference 5

Reference 6

Reference 7

Reference 8

Reference 9

Reference 10

Reference 10a

Reference 11

Reference 12

Reference 13

Reference 14

Reference 15

Reference 16

Reference 18

Reference 19

Reference 20

Reference 21

Reference 22

Reference 23

Reference 24

Reference 25

Reference 26

Reference 27

Reference 28

Reference 29

Reference 30

Reference 31

Reference 32

Reference 33

Reference 34

Reference 35

Reference 36

Reference 38

146 kPa 48

66 kPa 45

0

20

40

60

80

100

120

140

160

180


Wat

er c

onte

nt

Suction kPa

(a)

(b)



Wat

er c

onte

nt

suction

value

Drying

Wetting



After water entry

65 kPa 144 kPa

Residual

Water entry




0 26 56
























































Table 1

Table 2

Figure 1

Figure 2

Figure 3

Figure 4

Table 3

Figure 5

Figure 6

Figure 7

Table 4

Reference 1

Reference 2

Reference 3

Reference 3a

Reference 4

Reference 3b

Reference 5

Reference 6

Reference 7

Reference 8

Reference 9

Reference 10

Reference 10a

Reference 11

Reference 12

Reference 13

Reference 14

Reference 15

Reference 16

Reference 18

Reference 19

Reference 20

Reference 21

Reference 22

Reference 23

Reference 24

Reference 25

Reference 26

Reference 27

Reference 28

Reference 29

Reference 30

Reference 31

Reference 32

Reference 33

Reference 34

Reference 35

Reference 36

Reference 38





















































Table 1

Table 2

Figure 1

Figure 2

Figure 3

Figure 4

Table 3

Figure 5

Figure 6

Figure 7

Table 4

Reference 1

Reference 2

Reference 3

Reference 3a

Reference 4

Reference 3b

Reference 5

Reference 6

Reference 7

Reference 8

Reference 9

Reference 10

Reference 10a

Reference 11

Reference 12

Reference 13

Reference 14

Reference 15

Reference 16

Reference 18

Reference 19

Reference 20

Reference 21

Reference 22

Reference 23

Reference 24

Reference 25

Reference 26

Reference 27

Reference 28

Reference 29

Reference 30

Reference 31

Reference 32

Reference 33

Reference 34

Reference 35

Reference 36

Reference 38

applicability and accuracy of the initially dry and …...technical note applicability and accuracy...

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