# Strength Prediction Model for Cohesive Soil-Rock Mixture with Rock Content
## 1 Introduction
[17] employed the finite-difference software FLAC to model blocks as regular polygons (e.g., circles, squares, and triangles) to establish a two-dimensional stochastic fine structure model for SRMs and carried out a series of uniaxial compression numerical tests. [PERSON] et al. [18] analyzed the development of shear zones in granular geotechnical materials subjected to shear using the numerical tests that integrated discrete and finite methods. [PERSON] et al. [19] established a finite element model for rainfall infiltration on SRM slopes, and analyzed unstable rainfall infiltration scenarios in both homogeneous and inhomogeneous media. [PERSON] utilized FLAC to model SRMs as two-phase composites consisting of rock blocks and a soil matrix. [PERSON] et al. [20] investigated the stability of SRMs during excavation by integrating a 3D fracture system model into discrete element software PFC3D (V-3.0). [PERSON] [21] developed a hybrid DEM/FEM model to study the mechanical behaviors of geotechnical materials, where the soil or rock mass was treated as a system of discrete spheres. [PERSON] et al. [22] simulated the deformation characteristics of SRMs under different temperatures using the FLAC3D (v.2.10), and analyzed the effect of temperature on pore water pressure, deformation, and displacement. [PERSON] et al. [23] conducted numerical drained and undrained triaxial compression tests under different confining pressures and initial porosities using discrete element polyhedral cells. In summary, extensive research on in situ shear tests, laboratory large-scale triaxial compression tests, and numerical simulations concerning the mechanical properties of SRMs has been conducted, yielding results that can provide valuable guidance for practical engineering applications. Nonetheless, notable deficiencies remain in the study of SRMs within fault fracture zones:  
1. There are few current studies into SRMs in deep fault fracture zones, where sampling poses significant challenges, necessitating alternative materials to simulate fault mud. 2. Standard large triaxial compression testing machines introduce size effects on SRMs in fault fracture zones with block sizes of 25-270 mm [24; 25]; therefore, large triaxial compression tests are required to assess the impact of sample size on the mechanical properties of SRMs, thereby mitigating the influence of size effects. 3. The limited number of laboratory triaxial compression tests prevents generalization to fault fracture zones comprising various fault mud types and different P\({}_{\text{BV}}\) values in SRMs. The use of the discrete element technique allows for the reproduction of laboratory triaxial compression tests for SRMs, the calibration of interaction models and mechanical parameters between the rock block and the soil matrix, and the analysis of influencing factors, which can be extended to a wider range of SRMs. To address these issues, this study conducted laboratory large-scale triaxial compression tests on SRM samples with dimensions of 500 \(\times\) 1000 mm to investigate the effects of confining pressure, P\({}_{\text{BV}}\), and \(\alpha\) on their mechanical properties. Subsequently, a numerical model considering P\({}_{\text{BV}}\) and \(\alpha\) was established using discrete element software PFC\({}^{\text{3D}}\) (v.6.0) to facilitate the microsimulation study of the cohesive SRM. Finally, a strength prediction model was derived for the cohesive SRM based on P\({}_{\text{BV}}\).