MESOSCOPICAL STUDY ON INTERFACE PROPERTIES BETWEEN GEOMEMBRANE AND SOIL

Geomembrane has been commonly used as barriers in landfills in combination with soils. However, the soil-geomembrane interfaces may become the potential planes of weakness within the system along which failure may occur. Therefore, many laboratory tests have been conducted by researchers to investigate the interface shear behaviors. However, it is difficult to directly investigate the material interactions and mechanisms occurring at soil-geomembrane interfaces through common laboratory tests. In order to investigate the mesoscopical interface properties between geomembrane and soil, a serial of numerical direct shear tests are carried out using a modified three dimensional DEM code, EsyS-particle. In this paper, the sand is modeled with cohesionless frictional interactions, while the geomembrane is modeled with bonded particles. In order to precisely simulate the smooth surface of the geomembrane, the distance between two nearest bonded particles has been adjusted to a small value. Suitable mesoscopic discrete element parameters of the sand and geomembrane have been calibrated by numerical triaxial tests and tensile tests, respectively. The numerical interface direct shear tests are performed under the same conditions as the laboratory tests, and the simulation results are compared to experimental data. The DEM simulation result shows that the DEM simulation is capable of reasonably predicting interaction behavior between geomembrane and soil. The shear band thickness is approximately 2 times of the average particle diameters. During the shear process, the particles inside the band undergo large horizontal relative displacements, while particles outside the area are driven by an upward motion. And the void ratio inside the shear band sees an increasing trend during the shear process, whereas no obvious change is observed outside the area. The distributions of contact force chains are small and homogeneous at the beginning of the shear, during the shearing, the contact force chains are concentrating to the left part of the sample, and the orientations of the forces changed from nearly vertical to diagonal.