Semi-Analytical Solution for Energy Evolution Induced by Deep Rock Tunnel Excavation Considering the Nonlinear Behavior of Surrounding Rock

Energy dissipation is a fundamental characteristic of rock failure, and energy-based analysis methods have been increasingly applied in various rock engineering contexts. However, comprehensive studies on the complete energy evolution process of surrounding rock failure induced by deep tunnel excavation remain limited. Considering the effects of intermediate principal stress and the dilatancy behavior of plastic surrounding rock, this study derives, validates, and optimizes an elastoplastic analytical method that incorporates the triaxial stress path and nonlinear behavior of surrounding rock. Based on the principle of energy dissipation, a semi-analytical energy solution accounting for longitudinal excavation effects is further established. The energy evolution and damage development within surrounding rock under tunnel excavation are analyzed for rock masses with different properties. Results indicate that under high in-situ stress conditions, tunnel excavation in elastic-brittle hard rock triggers a rapid surge in the damage variable beyond 100% once the energy storage limit is surpassed, causing brittle failure and sudden energy release toward the cavity, with a fully damaged zone swiftly forming along the longitudinal direction as the excavation face progresses. In contrast, soft rock tunnels display a more gradual damage progression, where the maximum damage variable often remains below 100%, and energy is primarily dissipated through crack propagation and extrusion deformation, leading to a broader range of energy dissipation and significant macro-level deformation, despite a lower longitudinal energy evolution rate. In practical engineering, energy-based analysis proves valuable for developing early warning systems and designing tailored measures to address diverse geotechnical hazards.