Analysis of Deformation Characteristics of Layered Rock Tunnel Excavation Based on Statistical Mechanics of Rock Masses

Layered rock mass is prevalent in tunnel engineering, where deformation and failure of surrounding rock are primarily governed by discontinuity structural planes, leading to significant anisotropy in deformation and strength characteristics. Compared to continuous homogeneous rock masses, layered rock masses exhibit more complex engineering properties. This study utilized the constitutive theory of statistical mechanics of rock masses (SMRM) and Abaqus numerical software to analyze the influence of geometric, spatial, and mechanical characteristics of discontinuity structural planes on the stability of surrounding rock. The failure characteristics of tunnel surrounding rock with varying scales and orientations of carbonaceous slate discontinuity structural planes are examined. Additionally, the displacement distribution of surrounding rock under continuous medium conditions is compared between the SMRM constitutive theory and the Mohr–Coulomb constitutive theory. The results reveal that the SMRM constitutive theory aligns well with the Mohr–Coulomb theory under continuous medium conditions. The presence of discontinuity structural planes significantly diminishes the self-stability of the surrounding rock, with increased scale and density of structural planes amplifying their control effect. The direction of surrounding rock failure postexcavation is closely related to the formation occurrence and horizontal stress, manifesting as tangential shear sliding failure along the discontinuity structural plane and normal bending compression shear failure of the bedrock. Meanwhile, the model test results are employed to validate the feasibility of SMRM theory. This study provides an important reference for the analysis of deformation and failure mechanisms of layered rock masses with different joint surface parameters.