About the author:

Shanghai Tunnel Engineering Co., Ltd., Shanghai 200032, China

Abstract:

The newly constructed Metro Line 8 in Zhengzhou crosses over the operational Metro Line2 running tunnel,with the minimum clearance of 1.45m, posing a significant risk to Metro Line 2. Inorder to ensure the operational safety of Metro Line 2, protective control measures of anti⁃pull pilescombined with cover plates and MJS grouting reinforcement are taken in overlapping areas of the twolines. Additionally, in⁃site monitoring and three⁃dimensional FEM numerical simulation are conducted toassess the potential deformation of Metro Line 2 running tunnel induced by the shield tunnelingconstruction of Metro Line 8. The research results show that the shield tunneling construction with smallclearance causes the existing tunnel to exceed the deformation limit; However, after implementingcomprehensive control measures of anti⁃pull piles combined with cover plates and MJS groutingreinforcement, the maximum uplift of the existing tunnel is approximately 3mm, meeting the deformationcontrol requirements. The uplift of the existing tunnel generally takes on a trapezoidal shape; The upliftat the intersection of the existing and new tunnels corresponds significantly to the variations in shieldtunneling construction on the left and right lines. The uplift caused by shield tunneling on one side isgreater than on the other side, but the final uplift at the two intersection points on the same line is roughlythe same. When the existing tunnel is adjacent to underground buildings, the uplift on the side of thetunnel adjacent to the building is smaller than that on the side not adjacent to buildings due to the constraint effect of the nearby structures.