Evaluation and experimental study on the sealant behaviour of double gaskets for shield tunnel lining

As waterproof joints are essential for shield tunnel segmental lining, double gaskets have been adopted for certain tunnel segments with high ground water pressure to prevent water leakage. To investigate the leakage behaviour of double gaskets in shield tunnel lining with joint opening and offset combination, mechanical and leakage tests were conducted on double gaskets subjected to water pressure. The linings are made of bolted and precast concrete with double gaskets, and the two gaskets are different sizes, but both have open bases. The mechanical test results revealed that three distinct phases are observable in the gasket load deformation curve, due to the process of gasket compression. Inappropriate design parameters for the gasket can result in the segment spalling around the gasket groove in field. In this study, improved parameters, including the diameter of circle hole inside the gasket and the hardness of the gasket, are presented with the goal of preventing segment damage. The experimental sealant test results demonstrated that the joint opening has a significant effect on the gasket leakage capacity: with increasing joint opening, the gasket sealant capacity decreases. The leakage mechanism of the double gaskets is also elucidated.