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

Abstract

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. This study on the deformation characteristics of layered rock tunnel excavation, based on SMRM, provides critical insights for tunnel engineering. It emphasizes the importance of detailed geological surveys to identify structural planes, which impact stability, and demonstrates how numerical simulations with Abaqus can predict excavation behavior, aiding in optimal design and cost-effective, safe construction. The findings highlight the need for targeted reinforcement strategies and validate the SMRM model’s alignment with established theories, offering confidence in its practical application and guiding future research to enhance geotechnical engineering practices. The research indicates that the scale and density of structural planes affect the self-stability of surrounding rock, necessitating local reinforcement and comprehensive support designs, especially in areas with prevalent structural planes. Additionally, understanding the failure direction related to formation occurrence and horizontal stress provides a basis for designing tailored support systems, enhancing tunnel durability and safety. This investigation can significantly improve tunnel design, ensuring robust and reliable structures in layered rock masses.