Effects of rock content and degree of compaction on interface shear characteristics of geogrid-soil-rock mixture

In order to investigate the shear characteristics of the interface between geogrid and soil in the soil-rock aggregation with different rock contents and degrees of compaction, a mono-shear test is carried out on the interface of geogrid-soil mixture with different rock contents by using a large-scale direct shear apparatus. The effects of five kinds of rock contents (0%, 25%, 50%, 75%, 100%) and three kinds of degrees of compaction (88%, 92%, 96%) on the shear strength and bulk deformation characteristics of the interface of geogrid-soil mixture are studied. Based on the laboratory direct shear tests, the discrete element analysis model for reinforced soil-rock mixture is established to explore the mechanism of interaction of the interface between geogrid and soil-rock mixture. The results show that the shear strength, internal friction angle and apparent cohesion of soil-reinforcedment interface increase first and then decrease with the increase of stone content from 0% to 100%, and reach the highest values when the stone content is 75%. The sample exhibits fairly apparent strain softening and dilatancy at high rock content. In addition, the higher the degree of compaction, the faster the shear stress increases and the higher the shear strength of the interface between geogrid and soil-rock mixture. The numerical results show that the force chains of the low rock content model are thinner and more dense, while the force chains of the high rock content samples are thicker and more sparsely distributed, and the two groups of models are formed through strong chains after shear failure. During the shear process, the samples with high rock content will form a zone with large porosity, and the pores on the shear plane develop from both ends to the middle until they are connected.