DEM simulation of geotextile-geomembrane interface direct shear test considering the interlocking and wearing processes

Geotextile-geomembrane interface has low shear strength and strain-softening characteristics which might induce progressive failure in landfills. The interlocking between asperities and filaments and wearing of them have significant influence on the interface shear behaviors between textured geomembrane (GMB) and thermally bonded nonwoven geotextile (TBNG), but the microscale mechanism has not been clearly revealed before. Using discrete element method (DEM), textured GMB with breakable asperities and TBNG made up of randomly distributed fibers are generated. The micromechanical parameters of the two materials and the interface are calibrated using existing experimental data. Parametrical study about asperity bonding level, inter-fiber bonding level and inter-particle frictional coefficient are conducted to quantitatively investigate the interlocking behavior on the scale of asperities and filaments. The asperity bonding level greatly affects the interlocking effect between asperities and geotextile matrix and plays a dominant role in shear mode (frictional behavior and interlocking behavior). The influence of inter-fiber bonding level on the interface shear behavior is significant for textured GMB with strong asperities and is negligible for smooth GMB. The shear strength and post-peak reduction level are enhanced with larger inter-particle frictional coefficient. The present study provides an applicable tool to investigate the microscale mechanical behaviors of TBNG-GMB interface.