A Comparative Numerical Study on Soil–Geosynthetic Interactions Using Large Scale Direct Shear Test and Pullout Test

Abstract

The direct shear test and the pullout tests are two widely used test procedures for determining the properties of the soil–geosynthetic interface. It is evident from the previous literature that the interface properties obtained from these tests differ considerably. In the present study, an attempt has been made to compare the interface properties obtained from the direct shear test and the pullout tests using the numerical simulations. A nonwoven polypropylene geotextile was used in the study. Three different types of sands with different fines content were considered. The analyses were carried using finite element package PLAXIS2D in two dimensional frameworks. Initially, the numerical model was validated with the existing literature and the validated model was used to study the interface behaviour of the sand-geotextile interface. The results revealed that the interface properties obtained from the direct shear test and the pullout tests vary significantly. The presence of the fines content in the soil reduces the frictional resistance of the soil-geotextile interface. The interaction ratio value was found to vary between 0.67 and 0.97 for different types of sand. The friction coefficient of the pullout test was about 50% of the friction coefficient value obtained from the direct shear test. The friction angles obtained from the pullout test were found to vary between 30 and 50% of the direct shear tests. However, the apparent cohesion of the pullout test was found approximately four times the cohesion value obtained from the direct shear test.