Abstract:

The features of a ribbed geomembrane and sandy soil interface in a landfill liner system were studied by comparing the results of an indoor experiment and a two-dimensional particle flow code (PFC$^{\rm 2D})$ simulation using the discrete element method. An interface drawing test of the ribbed geomembrane and sandy soil interface was conducted under different combinations of ribbed heights and temperatures. Then, the macroscopic stress-strain curves of the ribbed geomembrane and sandy soil interface, the changing rule of the displacement field of microscopic particles, and the stress field were investigated. The results showed that the tensile stress of the ribbed geomembrane and sandy soil interface was superior to that of the smooth geomembrane ($h =0$ mm) and sandy soil interface. The drawing stress limit of the interface increased with the increase in rib height, and decreased with the increase in temperature. In addition, the friction coefficient of the interface decreased with the increase in temperature. Simulation of the microscopic aspects (particle displacement and internal contact force) also corresponded with the results of the ribbed geomembrane and sandy soil interface drawing experiment. The soil particle displacement near the ribbed geomembrane and sandy soil interface was larger, and the overall particles moved to the top left. The sandy soil at the top after the rib had downward movement owing to the normal stress. With an increase in temperature or decrease in rib height, the displacement of sand particles near the ribbed geomembrane and sandy soil interface increased, and the interface stability between the ribbed geomembrane and sandy soil became negligible. The contact forces on the left side of the drawing model and near the ribbed geomembrane were larger, and gradually decreased to the upper and lower sides. With an increase in rib height or a decrease in temperature, the contact force around the interface between the ribbed geomembrane and sandy soil increased. The entire process of drawing the ribbed geomembrane and sandy soil interface from macroscopic to microscopic was described.

Key words: numerical simulation, ribbed geomembrane, drawing test, displacement, contact force