Soil-Rock Mixture (S-RM) are widely found in the mountainous areas of southwestern China. The study of rock mechanical properties of S-RM is of great significance for preventing and controlling landslides or other geological disasters. Due to the large differences in rock content and particle gradation, the mechanical properties of S-RM show significant scale effects. This article discusses the "Representative elementary volume" (REV) properties of the S-RM under the condition of different rock-soil volume ratios. Based on the indoor biaxial experiment, the paper firstly establishes a two-dimensional discrete element model suitable for S-RM; Secondly, considering the rock content, by numerical simulation method based on PFC discrete element software, a total of 126 sets of biaxial tests were performed to obtain the cohesion and internal friction angle of the S-RM. By analyzing systematically experimental data of PFC, the corresponding scale effect curves are fitting. After the samples overcome the scale effect, the REV laws of the S-RM under different control variables are obtained. The engineering scale of the S-RM samples is about 600×200 mm. In actual projects, this sample size can be selected for testing or numerical simulation to reduce the scale effect.
Soil-rock mixture was defined by Xu and Hu (2009) as an extremely inhomogeneous and loose geotechnical material composed of rocks with high strength at a certain engineering scale, pore spaces and soil particles. Soil-rock mixtures are widely distributed throughout China, especially in the southwest. Landslide mounds and rock piles commonly found in southwestern mountainous areas are mostly composed of soil-rock mixtures. Due to the inhomogeneity of soil-rock mixture, mechanical properties have large spatial variability so that the study of mechanical properties and ontological characteristics are very difficult. The study of soil-rock mixtures is significant for the prevention and control of geological hazards such as landslides and collapse.