Abstract:In order to study the stability of surrounding rock after tunnel support in a large-section circular tunnel excavated by a shield tunneling machine, the No.1 return air shaft of the South Six mining district in Yuwu Coal Mine is used as the engineering background. The theoretical analysis provides a basis for selecting the support parameters. Based on the Hoek-Brown strength criterion, the radius of the loosened zone of the surrounding rock in the 6.3-meter diameter tunnel is calculated to be 8.12 meters, and the radius of the plastic zone is 4.20 meters. Therefore, the tunnel support adopts an alternating rock bolt and tendon support system. Through tunnel monitoring, the support effectiveness is evaluated in depth by analyzing the roof separation, surface displacement, and the forces on the rock bolts (tendons). The results show that the tunnel mainly undergoes bottom-up deformation, with slight separation at the roof. The forces on the rock bolts range from 200 to 225kN, while the forces on the tendons range from 230 to 260kN, indicating that the stability of the shield-excavated circular tunnel is good and the support strength meets the requirements for tunnel usage.
