INFLUENCE MECHANISM OF IN-SITU STRESS STATE ON ROCK BURST PRONENESS OF DEEP-BURIED-CURVED TUNNEL IN QINGHAI-TIBET PLATEAU AND ITS ADJACENT REGION

The engineering projects of deep buried tunnels in different positions of tectonic active zone in previous research indicate that the stability of deep tunnels is deeply relevant to in-situ stress. To analyse the influence mechanism of in-situ stress state on rock burst proneness of deep-buried-curved tunnel in Qinghai-Tibet Plateau and its adjacent region,three-dimensional finite element numerical simulation is done to explore the combine action of the angle φ between the maximum horizontal principal stress orientation and tunnel axis,and lateral pressure coefficient K_H on the distribution of strain energy density and rock burst proneness. The results conclude that whenφ is about 45°,the change of φhas the greatest influence on the proneness of rock burst. When the maximum horizontal principal stress orientation is perpendicular to the tunnel axis,the change of K_H has the most significant effect on strain energy density of surrounding rock. When the maximum horizontal principal stress orientation is parallel to the tunnel axis,the change of K_H has the least influence on strain energy density of surrounding rock. The multivariate regression equation is verified by a number of typical deep buried tunnels in the Qinghai-Tibet Plateau and the surrounding area. The multiple regression equation can be applied to quickly evaluate the influence of φ and K_H on tunnel stability serving the tunnel planning and design efficiently.