Abstract: To optimize the supporting parameters of mined metro station, provide reference for design, and clarify the difference of supporting effect of anchor bolt under different prestress forces, a tunnel numerical model is established using FLAC3D. The anchor bolt tray section, free section, and anchoring section are simulated through the subsection assignment of anchor agent and link parameters, and the prestress is given. The anchoring effect of the prestress anchor bolt is compared with that of conventional one used in a mined metro station. The results are fed back in combination with field application and monitoring. The numerical results show the following: (1) The bolt prestress significantly reduces or disappears the tensile stress zone and reduces the plastic zone of surrounding rock. (2) The active support function that improving the stress state of surrounding rock is remarkable. (3) When the prestress reaches over 40 kN, the plastic area of the crown disappears, and the maximum tensile stress of the side wall is 36.3 kPa. (4) When the prestress reaches 80 kN, there is no plastic area in crown, and the maximum tensile stress of the side wall is reduced to 13.9 kPa, showing a remarkable effect. (5) The field monitoring data show that the maximum compressive stress of grid steel frame is 34 MPa, the maximum compressive strain of concrete is 249 με, the maximum settlement of crown is 2.3 mm, indicating that the tunnel is safe and stable under the support of prestress anchor bolt.

Key words: metro tunnel, prestress anchor bolt, numerical simulation, FLAC3D