Investigation of Time-Dependent Characteristics of EPDM Rubber Gasket Used for Shield Tunnels

This paper presents a series of experimental investigations on the time-dependent characteristics of ethylene-propylene-diene monomer (EPDM) under various temperatures and strain conditions. The time-dependent mechanical properties including relaxation modulus and creep compliance of EPDM are investigated through short-term experiments. Based on the time-temperature superposition principle (TTSP), a transformation method named as the time-temperature-strain/stress superposition principle (TTSSP) is proposed to obtain the long-term time-dependent characteristics. The master curves of TTSP are obtained via horizontal shifting of the curves of the relaxation modulus or creep compliance with time and the shift factors are fitted by the Williams-Landel-Ferry equation. The results show that TTSSP is suitable to predict the stress relaxation and creep behavior of EPDM. The results show that, after serving for 100 years at 15°C, the relaxation modulus could reduce to 44.7% under 10% strain, whereas the creep compliance would increase to 191.3% under 1 MPa stress.