Durability performance of shield tunnel joint sealing gaskets under compressive conditions

The long-term serviceability of shield tunnels may be compromised by the degradation of the sealing performance of ethylene propylene diene monomer (EPDM) gaskets, which can result in water leakage and reduced structural durability. However, the durability behavior of EPDM gaskets under combined water-rich and compressive conditions remains insufficiently understood. In this study, hydrothermal accelerated aging tests and mechanical performance tests were conducted on EPDM gaskets subjected to different compression levels to investigate the evolution of compression set and the deterioration of compression-related mechanical properties. A time-dependent aging model was then established using the compression set ratio as the degradation index to relate laboratory aging to the service life of compressed gaskets. The results show that compressive loading markedly accelerates gasket aging and induces substantial irreversible deformation, with the maximum difference in compression set exceeding fivefold. Residual performance decreases with aging time and is jointly affected by aging temperature and compression level. A rapid nonlinear decline is observed during the first 10 years of service, followed by a gradual slowing after 20 years. At the end of a 100-year service life, the residual performance under compression levels of 6, 12, and 18 mm is 0.824, 0.613, and 0.454, respectively. Overall, EPDM gaskets under water-rich compressed conditions present pronounced time-dependent degradation and high sensitivity to compression level, and the results provide a basis for sealing design, service-life prediction, and leakage risk assessment in shield tunnels.