IMPACT ON ROCK BLOCK BREAKAGE CHARACTERISTICS TO THE THICKNESS OF SHEAR BAND OF SOIL-ROCK MIXTURE

Soil-rock mixture(S-RM),as a typical surface sediment on slopes,frequently causes landslides of different scales. This study aims to further reveal the influence of rock content and normal pressure on the thickness of the shear band of S-RM through large-scale direct shear testing and numerical stimulation testing using the Particle Flow Code in Two Dimensions(PFC^2D). The experimental results indicate that the thickness of S-RM is significantly affected by the rock content,followed by the normal pressure,and is minimally influenced by the rock block size. The thickness of the shear band increases with an increase in rock content from 0 to 50%. The thickness of the shear band also increases with an increase in normal stress; however,a decreasing trend is observed after the normal stress exceeds 200 kPa. The normal stress before the formation of the S-RM skeleton presents a decreasing trend. Nevertheless,the thickness of the shear band maintains a continuous increasing trend in numerical analysis samples with unbreakable rock blocks. The main reason for the increment in the thickness of the shear band is the gear effect caused by the occlusion of large blocks. Stress concentration at the interlocking contact position with a high rock block proportion and high normal stress contributes to the breakage of interlocking edges,inhibiting the further increase of shear zone thickness. Conversely,in the numerical simulation testing of S-RM with a high rock proportion,continuously interlocking rotation for unbreakable rock blocks was observed,resulting in the deformation of the surrounding soil and rock blocks and enhancing the thickness of the shear band. The results presented in this paper could provide essential insights into S-RM deformation.