Failure of urban subway segments in coastal area and reinforcement effect of bonded steel plate: a case study in China

The construction of metro in coastal areas is prone to safety accidents when it encounters unfavourable geology. Serious water inrush and sand gushing occurred during the construction of the shield tunnel connection channel of Shenzhen Metro Line 20, resulting in extensive deformation and even cracking of the shield segment. With the event as the background, it is conducted in this article with a further analysis of the causes of sand gushing in the connecting channel. Using convergence displacement and crack width as indicators, the shield segments are classified as strong influence zone, moderate influence zone, weak influence zone and no influence zone. Furthermore, by combining numerical simulation and field investigation, the innovative method of epoxy bonded steel plate reinforcement is proposed. In particular, it should be noted that the steel plate needs to be opened at the connection channel, so four small right-angle steel plates are designed to reduce the concentrated stress of the split ring. According to finite element analysis and on-site measurement, it can be known that after the steel plate is reinforced, the internal force of the segment is greatly reduced, and the deformation is stable, which can ensure the safe service of the tunnel. This research provides a new idea for the damaged reinforcement of urban subway segments in coastal areas in the future.