Objective After exiting the shield tail, tunnel segments are prone to uplift due to the combined action of synchronous grouting and surrounding water and soil pressures, including dislocation at the circumferential joints, which in turn leads to concrete damage at the joints. To suppress segment dislocation and control uplift deformation, thereby reducing their adverse effects on the structural safety and durability of the tunnel, it is necessary to further reveal the mechanism of segment uplift-dislocation and explore effective construction control methods.

Method Taking the Airport Link Line project of Shanghai Rail Transit city lines as an example, a three-dimensional finite element analysis model for the stratum-grout-tunnel segment interaction considering the shear resistance characteristics of the circumferential joints is established, and the model is verified using field measurement data. Based on this numerical model, the variation law and key influencing factors of segment uplift-dislocation are analyzed, targeted control measures are proposed, and their control mechanisms and implementation effects are examined.

Result & Conclusion  The established nonlinear shear spring model for the joint can well characterize the shear mechanism behaviors of inclined bolts and shear pins during the segment uplift-dislocation process. The segment dislocation amount reaches its peak immediately after exiting the shield tail; as the grout solidifies, the dislocation amount gradually decreases. Methods such as shortening the initial setting time of the grout, reinforcing the stratum, reasonably increasing the vault grouting pressure, optimizing the longitudinal force and bolt preload, and applying surcharge loading at the shield tail can all effectively control the segment uplift-dislocation amount.