Study on the grouting repair performance of shield tunnel segments based on high-fluidity slurry

Structural damage to shield tunnel segmental linings poses a significant threat to the safety and serviceability of urban rail transit systems. To address this issue, a drilling and grouting reinforcement technique was proposed, and its effectiveness was verified through full-scale experimental investigations. Flexural failure mechanisms of the segmental linings have been analyzed, and the load-bearing performance before and after reinforcement has been compared. Based on elastoplastic theory, a calculation method for estimating the load-bearing capacity of unreinforced segments has been developed and validated against test data, showing good agreement. The results indicate that grouting reinforcement significantly improves the structural behavior of damaged segments: the peak load increased by 9.4%, the ultimate failure displacement grew by 68%, and the load-displacement curve exhibited an extended plateau, demonstrating enhancements in both load-bearing capacity and ductility. The proposed method effectively prolongs the elastoplastic development stage and suppresses crack propagation. The difference between theoretical predictions and experimental results was within 10%, confirming the reliability of the model. This study demonstrates that drilling and grouting reinforcement is an effective technique for repairing damaged shield tunnel segmental linings, enhancing structural safety, and extending service life, thus providing theoretical support for tunnel structural rehabilitation and maintenance practices.