Investigation of the seepage property of a concrete fracture in a marine environment

Abstract

Concrete fractures, commonly considered as dominant flow channels in a submarine immersed tunnel at the stage of damage, greatly influence the structural long-term service performance in a marine environment. This study investigates the coupled process of the chemical interaction and the fluid flow behavior in concrete fractures, based on seepage tests of specimens experiencing immersion processes in an artificial marine environment with a depth of 50 m below sea level. The salt ion ratio used in the immersion tests comes from the field data of the actual marine environment where locates the immersed tunnel of the Hong Kong–Zhuhai–Macao Bridge immersed tunnel. Seventy cylindrical concrete specimens with dimensions of 25 mm × 50 mm are prepared, and each specimen is split to obtain a rough-walled fracture. The specimens are evenly divided into seven groups with different immersion periods, and the variation of the equivalent hydraulic apertures as well as the reaction products after the immersion tests of the concrete fractures are investigated. The surface morphology and composition analyses along the fracture surfaces indicate that the chemical reaction products during the immersion process are gypsum and ettringite. Furthermore, the variation results of the hydraulic properties indicate that the permeability of concrete fractures gradually reduces as the immersion period increases, and the equivalent hydraulic aperture varies less for the concrete fracture with relatively high roughness. An equivalent seepage model for a concrete fracture in a marine environment is then established to evaluate the equivalent hydraulic aperture considering the immersion environment and the fracture geometry, which provides a theoretical basis for analyzing seepage properties of concrete fractures in a marine environment and the long-term service performance of a submarine immersed tunnel.Kindly check and confirm whether the corresponding affiliation is correctly identified.The corrsponding  affiliation is correcly identified.