Sensitivity analysis of rock mechanics parameters in stability of tunnel surrounding rock

In this paper, we adopted the orthogonal numerical test method to study the effect of rock mass parameters on horizontal convergence, roof-to-floor convergence and plastic zone factor with select six factors, three levels test scheme, and the test results were analyzed by variance analysis method. The results show that the primary and secondary factors affecting the horizontal convergence is cohesion, elastic modulus, internal friction angle, tensile strength, and Poisson's ratio. The primary and secondary factors affecting the roof-to-floor convergence are cohesion, internal friction angle, elastic modulus, tensile strength, and Poisson's ratio. The primary and secondary factors affecting the plastic zone factor are internal friction angle and cohesion, while density has little or no effect on the stability of tunnel surrounding rock. The numerical simulation test results are consistent with the orthogonal test results after changing the mechanical parameters of any rock mass. With the increase of buried depth and lateral pressure coefficient, the horizontal convergence, roof-to-floor convergence and plastic zone factor increases gradually. When lambda < 1, the plastic zone distribute in a "flat" shape. When lambda = 1, the plastic zone is uniformly distributed. When lambda > 1, the plastic zone is "tall" shaped distribution. In view of the characteristics of V-grade surrounding rock of Sanquan tunnel in Chongqing, we proposed the initial support, waterproof layer, secondary lining + inverted arch filling support method. And we adopted the numerical simulation and monitoring measurement technology method to verify the supporting effect, the deformation of the surrounding rock is smaller and the surrounding rock is in stability state.