海水对隧道管片接缝橡胶密封可靠性的影响评估OA

[Objective]To explore the performance evolution pattern and service reliability of ethylene propylene diene monomer(EPDM)gaskets used in segment joints of cross-sea shield tunnels in a complex seawater chemical environment.[Methods]Four kinds of salt compounds(NaCl,MgCl2,Na2 SO4,CaCl2)with the highest contents in seawater were selected as corrosive media,and laboratory accelerated aging tests were conducted at different temperatures(50,70,90℃).[Results]Based on the analysis of the degradation characteristics of rubber mechanical properties,the Anderson-Darling test criterion was introduced to determine the optimal degradation distribution function,and a reliability evaluation model for rubber gaskets was constructed by integrating the accelerated stress levels and the aging time.Furthermore,the reliability life of rubber under different salt environments was derived and compared.[Conclusion](1)Salt corrosion leads to hardening and embrittlement of rubber materials.Macroscopically,the hardness increases with exposure time,while the tensile strength and elongation at break decrease.Among these,the corrosive effect of Na2 SO4 solution is the most severe,with the maximum reduction in elongation at break reaching 12.4％during the test period,while the short-term corrosion rates of MgCl2 and NaCl are relatively low.(2)The Weibull distribution model is most suitable for describing the statistical characteristics of the degradation of rubber elongation at break.The reliability curve derived from this distribution reveals stage-specific differences in the effects of different salts on rubber life.(3)The degradation of rubber properties by Na2 SO4 is mainly manifested in the early service stage.When the reliability requirement is high(R=0.990),the onset time of degradation induced by Na2 SO4 occurs earliest.For engineering scenarios requiring long service life(corresponding to lower reliability thresholds),the long-term cumulative corrosion effects of MgCl2 and NaCl gradually dominate,and they are the key factors determining the long-term waterproof safety of the gaskets.