The Influence of Different Water Contents on the Shear Mechanical Properties of the Soil-Rock Mixture-Bedrock Interface

During highway construction, a large number of soil-rock slopes are often formed, which are prone to sliding along the soil-rock interface under rainfall conditions, adversely affecting highway infrastructure and vehicle traffic. To investigate the shear mechanical properties of the soil-rock interface in cut slopes in the Ili region of Xinjiang, direct shear tests were conducted on the soil-rock mixture-bedrock interface under varying water contents and normal pressures. The study examined the relationship curves of interfacial shear stress versus shear displacement, as well as the variations in shear modulus, friction angle, and cohesion. The results indicate that, influenced by water content and normal stress, the interfacial shear stress-shear displacement relationship curves generally exhibit weak strain-hardening characteristics. In the initial stage, the interfacial shear stress increases gradually with the increase in shear displacement. As shear displacement continues to increase, the growth rate of interfacial shear stress gradually slows and eventually stabilizes, with stabilization occurring earlier under lower normal pressures compared to higher normal pressures. The interfacial shear modulus shows a clear decreasing trend with increasing water content. The interfacial friction angle decreases linearly with increasing water content, while the interfacial cohesion initially increases with rising water content, then slightly decreases after reaching a peak. Finally, the Duncan-Chang hyperbolic model was used to fit the interfacial shear stress-shear strain relationships of the soil-rock mixture-bedrock interface under different water contents. The fitting results reflect the weak strain-hardening characteristics of the interface. The research findings can provide data references for stability analysis of cut slopes in the Ili region of Xinjiang.