Time-dependent performance and constitutive model of EPDM rubber gasket used for tunnel segment joints

The waterproofing performance of rubber gaskets degrades with time and exerts a great influence on the water resistance of tunnel segment joints. As such, the time-dependent performance of rubber gaskets is an important study topic. Based on the service environment of tunnel segment joints, an accelerated ageing test was performed for EPDM rubber in groundwater environment to obtain the rule of its performance degradation. In this study, a time-dependent constitutive model of an ethylene propylene diene monomer (EPDM) rubber gasket used for segment joints was proposed according to the change rule of the mechanical properties of materials after ageing, and the results of laboratory-scale ageing tests were used to obtain expressions of the time-dependent parameters of the rubber gasket in the model. The transformation relations between time and temperature of material ageing in the laboratory and service environment were subsequently established. Finally, the established model was used to analyse the time-dependent parameters of EPDM and determine the attenuation rule of its mechanical properties. When the increase rate of model parameters exceeded the degradation speed of material performance, stress relaxation influenced the performance degradation of segment joints.