Development of a Shear Damage Constitutive Model and Dynamic Slip Numerical Program for Soil‒Rock Interfaces Based on Shear Tests

Current analyses of excavation stability in soil and rock strata do not account for strength degradation due to interfacial sliding offset, resulting in errors. In this work, the morphological characteristics of the soil‒rock interface are statistically characterized, the shear mechanical properties and damage characteristics of the interface are elucidated through shear tests, a shear damage constitutive model is constructed, and an interface dynamic slip numerical program is developed. The main conclusions are as follows: (1) With increasing normal pressure, water content, and interface relief, the peak shear stress τp at the non-cohesive soil‒rock interface shows linearly increasing, first increasing then decreasing, and bilinear increasing trends, respectively. In contrast, τp at the cohesive soil‒rock interface shows linearly increasing, linearly decreasing, and bilinear increasing trends, respectively. (2) There are three failure modes in both sandy soil and cohesive soil at the interface with the rock strata, with the cohesive soil also accompanied by diagonal compression shear cracks. (3) The descriptive effect of the constitutive model is satisfactory for all test groups. (4) Considering the dynamic mechanical behavior of the soil‒rock interface, the interface breaks off and slides with formation deformation, which is consistent with the actual situation.