Cyclic and post-cyclic direct shear behaviors of geogrid-sand interface with different soil densities

In order to investigate the cyclic and post-cyclic shear behaviors of geogrid-sand interface with different soil densities, a series of large-scale monotonic direct shear tests, cyclic direct shear tests and post-cyclic monotonic direct shear tests are performed using a large-scale direct shear device. Comparison and analysis are made between the results from monotonic direct shear tests and post-cyclic monotonic direct shear tests. The results show that the interface shear strength increases with soil density, and more evident dilatancy is observed with higher soil density in the monotonic direct shear tests. The degradation of cyclic shear stress is observed in the geogrid-dense sand interface, the soil tends to be contracted when suffering from cyclic shear, and the volume contraction increases with soil density. The interface shear strength tends to be strain softening, and the soil exhibits dilatancy throughout the tests in the post-direct shear tests with different soil densities. The degradation of the post-cyclic shear is observed in the dense sand-geogrid interface.