Numerical and statistical assessment of block-matrix interface parameters on the stability of soil-rock mixtures slopes

The presence of soil-rock mixtures (SRM) in slopes poses significant design challenges due to their heterogeneous composition. While volumetric block proportion (VBP) and mechanical properties of soil matrix are known key factors affecting SRM slope stability, the influence of the interface between soil and rock blocks has received less attention. This study undertakes a comprehensive numerical investigation using the finite element method (FEM), combined with statistical analysis, to explore the effects of block-matrix interface parameters including cohesion, friction angle, normal stiffness and shear stiffness on SRM slope stability. Given the significant role of VBP and block geometric arrangement, the influence of interface parameters is evaluated across different VBPs and block arrangements. Results indicate that for VBPs exceeding 25%, an increase in VBP leads to substantial enhancement in factor of safety (FoS) as the failure zone is diverted into a more tortuous path. To statistically examine the importance of interface parameters, response surface methodology (RSM) and analysis of variance (ANOVA) are employed. Statistical analyses confirm that VBP is the most significant parameter controlling slope stability, and it modulates the influence of other parameters. An increase in interface cohesion and friction angle elevates the FoS, with their effects becoming more pronounced at higher VBPs. Although the normal and shear stiffness of interfaces can alter deformability and stress distribution, they do not have a significant effect on the slope stability. Furthermore, it is demonstrated that increased block density can reduce the FoS, while larger rock block sizes significantly increase heterogeneity.