Resilience evolution of shield tunnel structures under ground surcharge

The proposition and development of the resilience theory provide a new way for the performance evaluation of shield tunnel structures. On the basis of the proposed lining performance index considering the maximum historical deformation, a refined 3D finite element model including segments, joints, and nonlinear soil springs is established. The structural response and resilience evolution of shield tunnels with different buried depths under surcharge and unloading are studied. The results show that under the ground surcharge, the inner surfaces at the arch crown and arch bottom, as well as the outer surface at the arch waist, are tensioned. Affected by staggered joints, the structural internal force and damage are more concentrated in the segment of the central ring adjacent to the longitudinal joint of the side ring. At the unloading stage, the horizontal convergence of the tunnel decreases, and the residual deformation after complete unloading increases with the increase of the surcharge. Under the same horizontal convergence, the deformation recovery rate of the shallow burial tunnels after unloading is greater. The resilience of the tunnel structures decreases quickly with the increase in the horizontal tunnel convergence, and shortening response time and improving the efficiency of repair measures can help enhance the resilience of the tunnel structures. While the resilience of the tunnel structures is divided into four levels, more efficient, rapid and comprehensive repair measures should be adopted to avoid the secondary damage to the structures when entering the extremely low resilience stage.