DEM investigation on mechanical behavior of geogrid-sand interface subjected to cyclic direct shear

The cyclic properties of geosynthetic soil interface are crucial for reinforced soil structures subject to seismic loading. To investigate the mechanical geogrid-sand interface behavior under cyclic shear conditions, a series of numerical simulation cyclic shear tests were conducted using the discrete element method. The results revealed with increasing of shear cycles, dense sand sample gradually shrunk, exhibiting obvious softening characteristics. The vertical displacement of the sample under simulated 10 cyclic shear increases by 0.27 mm, which is 0.41 mm lower than that under 1 cyclic shear. Meanwhile, obvious dilation was observed in the shear band. As the number of cyclic shear increases, the region where the particle rotation occurs does not change significantly, ranging from 75 mm to 125 mm. Higher sample density made it more difficult for particles at geogrid-sand interface to rotate. Under the same number of cycles, denser samples had narrower shear bands, smaller shear strain shifts, and larger shear stiffness. The sand size is 0.5 mm, and the particle displacement concentrated in the 3 mm shear zone. After the completion of cyclic shear, dense sand had little effect on the porosity of the unreinforced sand affected zone, and the porosity after cyclic cycle was close to the initial porosity.