Pullout Resistance of Geotextiles With and Without Wicking Function

Samuel Kaluzny

Dans les comptes rendus d’articles de la conférence: GeoVancouver 2016: 69th Canadian Geotechnical Conference

Session: GEOSYNTHETICS

ABSTRACT: Geotextiles have been commonly used as slope and basal reinforcements to improve the stability of embankments.Slopes are exposed to natural events such as seasonal wetting and drying as well as freezing and thawing. Water thataccumulates in the slope reduces its shear strength, thus increasing the embankment•s susceptibility to slopemovements. The performance of a woven geotextile with wicking capabilities is evaluated. The wicking function of thegeotextile provides in-plane drainage for the water to flow out of the embankment. The wicking geotextile is compared tothat of a geotextile with similar stiffness and surface texture but without the in-plane drainage capability. A series ofpullout tests at different confining pressures were tested for both geotextiles (wicking and non-wicking) to study the effectof the in-plane drainage to the shear stiffness and strength at the soil-geotextile interface. The tests were conducted withsoils compacted at 95% of the maximum dry density on the wet side of the optimum moisture content. Telltales wereused to measure relative displacements and strain distributions along the length of the geotextile. Earth-pressure cellsand suction sensors were installed close to the geotextile. Tests were only conducted along thecross-direction parallel tothe direction of wicking.This paper presents the results of the testing program.R†SUM†Les g‡otextiles sont couramment utilis‡s comme renforts de pente et de base pour am‡liorer la stabilit‡ des remblais.Les pentes sont expos‡es … des ph‡nom—nes naturels tels que les cycles saisonniers de mouillage et de s‡chage ainsique de gel et de d‡geldu sol. L'eau accumul‡e dans la pente diminue la r‡sistance au cisaillement du sol et parcons‡quent augmente la sensibilit‡ du remblai aux mouvements de pente. La performance d'un g‡otextile tiss‡ avec descapacit‡s hydrofuges est ‡valu‡e. Les propri‡t‡shydrofuges du g‡otextile permettent le drainage de l'eau en dehors duremblai. Le g‡otextile hydrofuge est compar‡ … un g‡otextile avec une rigidit‡ et une texture superficielle similaires, maissans la capacit‡ de drainage. Une s‡rie d'essais d'arrachement … diff‡rentes pressions de confinement a aussi ‡t‡r‡alis‡e pour les deux g‡otextiles (hydrofuge et non-hydrofuge) dans le but d•‡tudier l'effet de l'‡coulement sur la rigidit‡et la r‡sistance au cisaillement … l'interface sol-g‡otextile. Les essais ont ‡t‡ r‡alis‡s avec des sols compact‡s … 95% dela densit‡ s—che maximale sur le c–t‡ humide de la teneur en eau optimale. Des t‡moins ont ‡t‡ utilis‡s pour mesurerles d‡placements relatifs ainsi que les distributions de d‡formation le long du g‡otextile.Des cellules de pression et descapteurs de succion ont ‡t‡ install‡s … proximit‡ du g‡otextile. Les essais ont ‡t‡ effectu‡s uniquement sur la directiontransversale parall—le … la direction des forces hydrofuges.Cet article pr‡sente les r‡sultats du programme d'essais.1INTRODUCTIONGeosynthetics are composed of polymeric-basedmaterials often manufactured as sheets used in a varietyof engineering applications in transportation,environmental, hydraulics, and geotechnical engineering(Koerner, 2005). Geosynthetics offer different functions toimprove a structures• design such as filtration, separationbetween native and backfill soil, providing confinement,drainage, and reinforcement, among others.Geosynthetics have been extensively used as part ofvarious structures including mechanically-stabilized earth(MSE) walls, embankments, lagoons, and basalfoundations. With the use of geosynthetics as aconstruction material, it has allowed a cost-effective andrapid approach to soil structure construction providing thenecessary design requirements set forth by the engineer.The most common types of geosynthetics used inconstruction are non-woven and woven geotextiles.Theyhave been commonly used as slope and basalreinforcements to improve the stability of embankments.Pullout tests are usually conducted to determine thepullout resistance of a geotextile and its interface frictionproperties.The pullout test replicates the behaviour of thereinforcement in a soil structure as shown inFigure 1.Resistance generated at the interface of the geotextileand soil allows the soil to transmit tensile stresses to thereinforcement(Wijewickreme & Weerasekara, 2010).Theprimary mechanism of geotextiles in pullout is thesoil-reinforcement interface friction(Alfaro et al., 1995).Several factors play a key role in the determination of thesoil-reinforcement interaction mechanismsuch assoilproperties (particlesize distribution and density)and themechanical properties of the geotextile(Lopes, 2002).Thispapercompares two woven geotextiles in bothtensile and pullout tests under different normal pressures.The difference between both geotextile reinforcement isthatone hasa wicking function (H2Ri) capable of in-planedrainage, and the other is a typical geotextilereinforcement (RS380i) without wicking (non-wicking)function. The H2Ri and RS380i are comparable as bothreinforcements exhibit the same tensile strengthat 2%strain, are composed of the same polypropylene filament,and are weaved in the same manner duringmanufacturing. With similar composition andmanufacturing practices changes of behaviour andstrength properties cannot be attributed to manufacturingtechniques(Boyle et al., 1996).

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