Study on rust layer distribution of cracked segment at tunnel arch waist under stray current and chloride ion corrosion

Abstract During subway operation, cracks may appear at the arch waist of tunnel segment surface. Under the acceleration of stray current, chloride ion in groundwater will penetrate into the surface of rebar through cracks, resulting in segment rebar corrosion and structural stiffness degradation. In this article, the rebar corrosion calculation model of tunnel segment contained transverse crack under stray current and chloride ion was established, and the coupling of electric field and chemical field in cracked concrete was realized. The effects of chloride ion content and input voltage on the rust layer distribution of cracked segment were studied. The results shows: Under the action of stray current and chloride ion, the 3D rust layer of cracked segments at the arch waist can be described by Gaussian mixture function. In the longitudinal direction, the rust layer at the crack section is located at the peak of the rust layer curve, and the increase of chloride ion content has a greater influence on the rust layer shape than the increase of stray current. When the chloride ion content and stray current are doubled, respectively, the maximum rust layer thickness of rebar will increases by 34% and 16%, respectively. In the circumferential direction, the nonuniform coefficient of elliptical rust layer will change with the increase of segment crack width and chloride ion content, but it will not be affected by stray current intensity.