Effect of Beaded Karst Caves Location on Stability of Tunnel Surrounding Rock

The special spatial structure of karst tunnels is due to the existence of beaded caves, which leads to the complexity of the stress-strain field of the surrounding rock, and the influence on the surrounding rock in the process of traversing the construction is unclear. Taking the Zhongliangshan Tunnel of Chongqing Rail Transit Line 27 is taken as the background of the project, and a three-dimensional numerical model is constructed based on the existing energy field visualization and analysis system to investigate the influence of the different locations of the caves on the stability of the tunnel surrounding rock. The results show that: The right side of the tunnel cavern has the most significant influence on the stability of the surrounding rock, and the vertical displacement of its arch foot is up to 50%, and the plastic zone is connected with the cavern area; when the cavern is located in the upper and lower part of the tunnel and the spacing is 5 m, the plastic zone is not connected; The energy evolution of the surrounding rock shows that the elastic strain energy around the support structure is released in a negative value, and the right cavern results in the formation of the dissipative energy density through the band; Based on the plastic zone through the criterion of the bead-like cavern safety protection thickness, it is proposed to be a safe and safe protection against the breakout. Based on the plastic zone penetration criterion, it is proposed that the thickness of the safety anti-protrusion of bead-like cavern should be more than 5 m.