Stress distribution and plastic zone characteristics in surrounding rock of deep tunnel under different principal stress directions

The change of principal stress in the process of tunnel excavation results in the change of stress distribution and plastic zone of surrounding rock, which significantly affects the stability and sup⁃ port of tunnel surrounding rock. In this paper, taking an elliptical tunnel as an example, the failure of surrounding rock under different principal stress directions was simulated. Based on complex variable functions and strength criterion, the analytical solution of surrounding rock stress under different principal stress directions and the plastic zone model were established. The results have shown that the maximum tangential stress is located between the top and bottom and the side wall, and with the increase of the depth from the free surface, the maximum tangential stress gradually approaches the direction of horizontal principal stress. With the increase of the angle between the principal stress direction and the tunnel, the concentration point of the maximum tangential stress at the free face gradually approaches the top and bottom of the tunnel. In addition, the damage region of the sidewall gradually decreases. As the angle between the principal stress direction and the tunnel increases, the plastic zone of the surrounding rock gradually moves away from the center of the sidewall, and the region and maximum depth of the plastic zone gradually decrease. Under different principal stress directions, the maximum depth of plastic zone is parallel or approximately parallel to the horizontal principal stress direction. © 2023 China University of Mining and Technology. All rights reserved.