Compressive stress-hydrothermal aging behavior and constitutive model of shield tunnel EPDM rubber material

Abstract

The damage and aging of the ethylene-propylene-diene monomer (EPDM) rubber material significantly impact the attenuation of the shield tunnel's waterproof performance. Furthermore, the compressive stress acting on the rubber material will further exacerbate this consequence. Therefore, it is necessary to explore the time-dependent properties of rubber under compressive stress. In this study, the EPDM rubber was subjected to compressive stress-hydrothermal aging (CS-HA) test at different pre-compression strains, temperatures, and time according to the application environment of the shield tunnel. The rule of compression set (CS) and the variation rule of mechanical properties of rubber materials after aging were investigated, and the reasons for these rules were analyzed. According to the rule of rubber material performance degradation, a constitutive model of EPDM rubber for shield tunnel segment squeezing environment was proposed. Using compression set as the index of material performance deterioration degree, the time and temperature conversion relationship between laboratory aging and service environment aging of the EPDM rubber segment joint was obtained. Furthermore, based on the constitutive model and related parameter expressions proposed in this paper, the attenuation rule of rubber mechanical properties and residual properties was obtained. It was proposed that the service performance of EPDM rubber under compressive stress should be considered when setting the pre-tightening force during the construction of the shield tunnel, and a reasonable pre-compression force should be adopted. This work provides an effective test method and constitutive model for predicting the time-dependent characteristics of the mechanical properties of rubber materials under compressive stress.