The soil rock mixture (SRM) material is an extremely inhomogeneous and unconsolidated geotechnical material composed of fine-grained soil and large-diameter rock blocks. It is widely encountered in infrastructure construction projects in the mountainous areas of western China, especially highways projects. Due to the complexity of the internal structure of the SRM slope, the traditional ultimate equilibrium theory has great difficulty in analyzing its stability. To study this problem, referring to the actual slope problem of one project, the structural characteristics of the SRM slope and the particle distribution condition of the rock blocks are obtained by using the PCAS (Particles and Cracks Analysis System) image processing software. Then the numerical simulation program MatDEM (Matrix computing of Discrete Element Method) is used to establish a discrete element model of SRM slope excavation. The simulation of slope instability and evolution process is carried out by the gravity increase method. And the analysis of slope excavation stability under different material and gravity conditions from aspects of slope morphology and sliding body motion has been developed. The research result shows that: (1) the existence of the rock blocks can reinforce the sliding resistance and increase the factor of stability of the SRM slope within a certain range, but the weak rock-soil interface contact may decrease the overall cohesion of an SRM mass; (2) the discrete element simulation of SRM slope can evaluate the stability of slope with safety factor conveniently, and it can reflect the interaction between rock and soil and the progressive process of slope failure more accurately than the ultimate equilibrium method.

1. Introduction

The Soil rock mixture (SRM) is a kind of complex geotechnical material which composed of finegrained soil, different-size rock blocks and pores. As a common geomaterial, SRM is widely encountered in infrastructure projects, especially in the mountainous area of western China. Many geoengineering accidents are related to this complex material, such as the recent landslide accident in Shuicheng County, Guizhou Province. Because of this special constitute characterized by extremely inhomogeneous and loose, the stability of the SRM slope cannot be analyzed by ultimate equilibrium theory or other traditional methods anymore. So, the stability of SRM slope has gradually become a research focus and challenge.

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