Cracking Performance of an Operational Tunnel Lining Due to Local Construction Defects

Local defects, such as surround cavities and insufficient thickness of the tunnel lining due to imperfect construction, will lead to local discontinuity in the ground–lining interaction. This study investigated the mechanical and cracking performance of an existing tunnel lining due to local construction defects. Field observation was carried out to detect the geometry and position of the local construction defects, whereas numerical analyses were performed to examine how these defects affected the stress distribution and cracking performance of the concrete lining. The development of cracking direction and distribution pattern on the existing tunnel lining due to the defects of local cavity and local insufficient lining thickness was demonstrated by using the extended finite-element method (XFEM). Scenarios with different construction defects were studied to account for the cracking performance at the interior and exterior sides of the existing tunnel lining. The results demonstrated that the local construction defect could lead the lining to local arch behavior, squeezing outward to the defect and consequently causing damages firstly at the invisible exterior side of the tunnel lining. The presented study demonstrated an effective way for modeling tunnel lining cracking and appropriately evaluating the actual cracking performance of the tunnel lining subject to local construction defects.