Research on Large Deformation Control Measures of Surrounding Rock in Jointed and Altered Granite Stratum of High Ground Stress Tunnel

Abstract

The large deformation of surrounding rock occurred frequently when Zangga tunnel passed through the high-stress jointed altered granite formation, and the deformation could not be controlled by the design scheme proposed in the initial stage of construction. Based on the monitoring results and geological data, this paper analyzed the deformation characteristics of jointed and altered granite in Zangga tunnel, and discussed the influencing factors of deformation. By means of a field test, the comprehensive control measures of surrounding rock deformation, which mainly includes adjusting the curvature of sidewall, combining long and short bolts and double-layer primary support, were studied. The results show that the deformation is characterized by large deformation value, fast deformation rate and long duration, and its tunnel convergence is greater than crown settlement. The influences of active fault on surrounding rock and alteration of surrounding rock are the internal causes of large deformation of the tunnel, while high ground stress is the external factor. The field test results show that the deformation value, rate and duration of surrounding rock can be controlled after the comprehensive control measures are adopted, and the construction efficiency is greatly improved.