An experimental study on durability of shield segments under load and chloride environment coupling effect

Abstract

Taking into consideration a shield tunnel’s environmental and mechanical properties, we designed a durability test method for its segment lining under the coupling effect of load and chloride environment (CEL&E). To verify the credibility of the method, we developed an environmental simulation test device and conducted durability tests on specimens using the test device. The results of the tests showed that with increased environmental chloride concentration and extended time period, the chloride ion content in the protective layer of the concrete increased gradually. It was also found that the external load changed the pore structure properties within the concrete, thus affecting chloride ion penetration. Considering that the load effect can change the structural characteristics of pores, we proposed a chloride diffusion coefficient evolution model for concrete under the CEL&E. By applying numerical fitting and using parameters of quadratic regression, we also established an equation for determining surface ion concentration under the coupling effect. Finally, we devised an evaluation model and calculation method for durability of a shield tunnel’s segment lining under the CEL&E. This calculation method can be used for assessing the concrete durability of existing shield tunnel structures, prediction of remaining service life, as well as durability design of new shield tunnel structures.