Shear Constitutive Model and Discrete-Element Verification Considering the Mesoscopic Characteristics of Aggregate in Soil–Rock Mixture

Soil–rock mixtures are composed of a complex heterogeneous medium, and its mechanical properties and mechanism of failure are intermediate between those of soil and rock, which are difficult to determine. To consider the influence of different particle groups on soil–rock mixture’s shear strengths, based on the mesomotion properties of the particles of different particle groups when the soil–rock mixture is deformed, it is classified into two-phase composites, matrix and rock mass. In this paper, based on the representative volume element model of soil–rock mixtures and the Eshelby–Mori–Tanaka equivalent contained mean stress principle, a model of shear constitutive of the accumulation considering the mesoscopic characteristics of the rock is established, the influence of different factors on the shear strength of the accumulation is investigated, and the mesoscopic strengthening mechanism of the rock on the shear strength of the accumulation is discussed. The results show that there is a positive correlation between the rock content, the surface roughness of the rock, the stress concentration coefficient, coefficient of average shear displacement, and the accumulation’s shear strength. When the accumulation is deformed, it stores or releases additional energy than the pure soil material, so it shows an increase in deformation resistance and shear strength on a macroscopic scale.