Plastic Zone Analysis of Tunnel Surrounding Rock Based on Hoek-Brown Criterion

Based on Hoek-Brown criterion,a formula for calculating stress displacement in elastic-plastic zone of deep circular tunnel considering stress redistribution（ without considering groundwater action） is derived. The influence of GSI,type of surrounding rock,support force and initial stress on the radius and displacement of plastic zone of surrounding rock is analyzed. When GSI is the same,no matter the type of rock,the initial in-situ stress has a great influence on the stress and displacement in the plastic zone of surrounding rock,especially when the initial in-situ stress is greater than 15 MPa. Accumulated subsidence value and the in-situ observation of surrounding rock loose circle range with the theoretical value calculated value analysis and comparison,the cumulative settlement of surrounding rock in the slope zone can be divided into serious disturbance,moderate disturbance and micro perturbation,and the plastic zone range is close to the actual observation and severe deformation of surrounding rock area from concentrated in surrounding rock indicates that within the scope of 0. 8 m. The deformation is about 90% of the theoretical calculation value,which can provide reference for similar projects in the future.