Deformation Behaviors and Control Measures of Tunnels in Jointed and Altered Granite Rock Mass with High In Situ Stress: A Case Study

Abstract

Large deformation of the surrounding rock may also occur in hard rock tunnels under certain circumstances. Taking the construction of the jointed and altered granite stratum in the Zangga Tunnel, China, as a case study, the paper analyzes the surrounding rock deformation characteristics and influencing factors in the jointed and altered granite stratum, and explores the control measures for the large deformation by the numerical analysis and the field application test. The results show that the accumulated deformation value and the deformation rate have large values, and the horizontal convergence is larger than the crown settlement. Geological reasons, such as an active fault and alteration, are the internal factors of large deformation, whereas the high in situ stress situation and other reasons are the external factors. The numerical analysis results show that the optimized support structure has the capability to control the deformation. Numerical analysis results show that the optimized structure can control the deformation and the plastic zone range. The field test results show that the deformation rate and value are well-controlled after adopting the control measures, and the field construction efficiency is significantly enhanced, indicating that the control measures presented have a good construction effect in this stratum.