Numerical Simulation Analysis Of Rockburst Tendency Of Deep-buried And High-in-situ Stress Tunnels

Deep-buried high-in-situ tunnels are affected by high in-situ stress and construction disturbance,and rockburst disasters frequently occur during the construction period.Rockburst has the characteristics of randomness,suddenness,and destructiveness,which seriously threatens the safety of tunnel construction.It is necessary to study and predict its damage degree and damage location.This paper takes the tunnel of the Qinling deep-buried section of the Qinling to Weihe River Diversion Project as the background,starting from factors such as the geostress condition of rockburst,the energy source of rockburst and the triggering effect of excavation disturbance,comprehensive application of field test,theoretical analysis and numerical value The simulation method carried out qualitative analysis and numerical simulation analysis on the rockburst tendency of hard and brittle surrounding rock during tunnel excavation.The content of this article includes the following aspects:(1)The three-hole intersection hydraulic fracturing method and the stress relief method in-situ stress measurement were carried out in the deep-buried cross-ridge section of the Qinling tunnel.The in-situ stress test results were compared with the geological structure conditions and the current tectonic stress field.The analytical method of spatial stereographic projection has been comprehensively analyzed.(2)Based on the principle of multiple linear regression,the initial in-situ stress field along the deep-buried tunnel was back-analyzed,and the intensity-stress ratio index was used to predict and evaluate the in-situ stress level and the tendency of rockburst during tunnel construction.The results show that the rock mass stress of the deep-buried tunnel section is classified as high in-situ stress to extremely high in-situ stress,and moderate rock bursts and strong rock bursts may occur during the construction period.(3)Aiming at the local diorite section of the tunnel with a buried depth of about1300 m and TBM construction,a three-dimensional numerical model was established based on the constitutive model of the brittle rock mass based on the weakening of cohesive force-the strengthening of friction force CWFS Moore Coulomb strength criterion.The stress characteristics and elastic strain energy of surrounding rock during the excavation process were simulated and analyzed.(4)Based on the energy index of rockburst discrimination and the empirical criterion of blast pit depth,predict the rockburst tendency of surrounding rock during tunnel excavation,such as rockburst intensity,damage location,and damage range.The results show that the deep-buried tunnel section is dominated by strong rockbursts,which is consistent with the on-site rockburst monitoring results,which verifies the rationality of the numerical simulation results.