Boundary Estimation of Tunnel Surrounding Rock Engineering Based on Mohr-Coulomb Criterion

In numerical modelling of tunnelling, the size of the numerical model, representing the range of engineering boundary for tunnel surrounding rock, is of great significance for tunnel stability analysis and design. Based on Mohr-Coulomb criterion, an estimation method was proposed for the engineering boundary range of tunnel surrounding rock considering rock mass quality, taking rock stress disturbance amplitude as a quantitative indicator. Rock masse of four quality levels were utilized to validate the estimation method. The results show that: The estimation method can be used to quickly predict the engineering boundary range for rock masses of different qualities, in which the estimation results for rock mass grade Ⅲ and Ⅳ are highly closed to the numerical results. Furthermore, the impacts of lateral pressure coefficient and excavation shape on the engineering boundary range were investigated. The results indicate the lateral pressure coefficient has an obvious effect while the excavation shape has a negligible one. This proposed estimation method provides advice for the accuracy of the numerical modelling design and analysis in underground tunnels.