Long-term waterproof performance of EPDM sealing gaskets considering aging-induced stress relaxation

The safety and reliability of the shield tunnel depend on the long-term waterproof performance of the gasketed joint, which is closely related to the aging behavior of the compressed gasket. In this study, the time-varying behavior and mechanism of the rubber properties of the gasket were comparatively analyzed through the aging tests conducted under different compression stresses. Based on the stress relaxation coefficient, a time-varying model for the aging performance of the gasket considering the joint opening was derived. Subsequently, a sensitivity analysis of the aging performance of the compressed gasket was conducted to identify key drivers. Finally, a nonlinear formula between the waterproof performance and contact stress was proposed by the waterproof test. The long-term waterproof performance of the compressed EPDM gasket was predicted based on established theories. The results show that the residual waterproof property of the gasket is closely related to pre-compression stress. The close holes of the semicircular or circular can avoid stress concentration in holes, reducing stress relaxation of the aged gasket. The joint opening has the greatest influence on the contact stress of the compressed gasket, followed by the aging temperature, and lastly the aging time. The loss of the waterproof performance of the compressed gasket is extremely significant during the first 50 years of service, and then gradually slows down as service time increases. When the joint opening is less than 8 mm, the waterproof performance of the compressed gasket decreases by over 50 % after 50 years, and by more than 60 % after 100 years of service.