Study on long-term waterproof performance and failure mechanism of shield tunnel gasket under compression

To study the long-term durability and failure mechanism of ethylene propylene diene monomer (EPDM) rubber gasket in shield segment joints under water-rich environment and compression. In this paper, the hydrothermal accelerated aging test of EPDM rubber gasket under compression was carried out, and the height loss and mechanical properties degradation of the gasket were revealed. Taking the height loss rate as the deterioration index, a time-varying model of gasket aging under water-rich and compressive conditions was established, and the conversion relationship between the test aging and the service life of the gasket under compression was obtained. Furthermore, based on the modified Mooney-Rivlin constitutive, an Euler-Lagrange coupling numerical model considering the effect of water flow is constructed, and the waterproof failure mechanism of the gasket after aging is analyzed. Finally, considering the influence of segment joint deformation in actual service, the evolution law of long-term waterproof performance of gasket under the action of joint dislocation and opening is predicted. The results show that the existence of compression force will seriously aggravate the aging of the gasket, resulting in significant irreversible deformation, and the height loss rate difference between the compressed and uncompressed gaskets is more than 10 times. The waterproof failure process of the gasket after compression aging can be divided into four stages: initial infiltration-splitting-penetrationleakage. During the actual compression service period, the residual performance of the gasket decreases nonlinearly with the increase of the service time, and the loss is extremely significant in the first 5 years of service, and then gradually slows down with the increase of time. In addition, when the joint opening reaches 6 mm, the effective service life of the gasket is shortened to 100 years, the opening amount is 12 mm, and the service life is reduced to 50 years.