# Strength Prediction Model for Cohesive Soil-Rock Mixture with Rock Content
## 1 Introduction  
A fault fracture zone forms as a result of ruptures and misalignments of rocks due to faulting caused by crustal movement [1]. The loose rock in these fracture zones leads to low load-bearing capacity, which may lead to issues such as sinking, tilting, or even the collapse of building foundations. These fault fracture zones are predominantly soil-rock mixtures (SRMs) composed of rock blocks with relatively high strength and stiffness, as well as fault mud with low strength, which is characterized by a directional arrangement and the inclusion of large-size blocks (25-270 mm). They may lead to hazards such as landslides, toppling, uplift arch bulging, supporting structure damage, or even the overall instability of tunnel lining structure [2]. Therefore, investigating the mechanical properties of SRMs is of paramount importance. Recent studies have predominantly focused on in situ shear tests, laboratory large-scale triaxial compression tests, and numerical simulation tests aimed at understanding the mechanical properties of SRMs in shallow landslides. In situ tests offer advantages such as ease of implementation, lower cost, and direct access to strength parameters from in situ samples. Several scholars have conducted research on SRMs through in situ shear tests. [PERSON] et al. [3; 4] and [PERSON] et al. [5] performed several sets of in situ horizontal push-shear tests and compressive shear tests in the Baiyian landslide belt within the Three Gorges Reservoir area. They obtained the damage modes, shear deformation curves, and shear strength of SRMs under different sample sizes, force conditions, and rock contents (\(\mathrm{P_{BV}}\)). [PERSON] et al. [6] conducted in situ tests to derive the stress-strain curves and shear strength parameters of SRMs under different conditions. [PERSON] [7] carried out a series of in situ large-scale push-shear tests to examine the influence of \(\mathrm{P_{BV}}\) on the mechanical properties of SRMs. [PERSON] [8] found that the shear strength of landslides substantially increases with the presence of larger sized blocks. [PERSON] [9] et al. conducted in situ horizontal push-shear tests under natural and submerged environmental conditions to analyze the effects of parameters such as water content, \(\mathrm{P_{BV}}\), and grain size distribution on the shear strength index of SRMs. In contrast to the complexities associated with in situ testing, laboratory testing allows for a more convenient and systematic exploration of the mechanical behaviors of SRMs under varying factors. [PERSON] et al. [10] prepared an artificial SRM within a test chamber and performed uniaxial and triaxial tests. [PERSON] et al. [11; 12] explored the effect of \(\mathrm{P_{BV}}\) on the shear strength and internal void ratios of SRMs, and found that the shear strength of SRMs is largely determined by the degree of aggregation between the stones and soil. [PERSON] et al. [13] conducted undrained shear tests and concluded that the strain softening characteristics of the samples were positively correlated with the gravel content. [PERSON] et al. [14] analyzed the mechanical properties of coarse-grained soils with different particle sizes and particle gradations. The results showed that the internal friction angle and the degree of shear expansion increased with increasing particle size. [PERSON] et al. [11] and [PERSON] et al. [15] investigated the effect of factors such as \(\mathrm{P_{BV}}\), the grading of SRM on its shear strength, deformation mechanism, and shear damage characteristics through laboratory large-scale direct shear tests. [PERSON] et al. [16] studied the effect of \(\mathrm{P_{BV}}\) on the deformation and strength of SRMs using a specially designed large-scale lateral limit consolidator for airport fill in the western mountainous area. However, technical challenges often arise during sample preparation for laboratory testing, which necessitates the use of numerical simulation as effective complements. [PERSON] et al.