Research On Corrosion Resistance Of Shield Segment Concrete Under The Action Of Multiple Factors

With the rapid development of urban rail transit,Xuzhou has become the fifth subway city in Jiangsu Province,and the segment is the basic structure of shield tunnel.This paper takes Xuzhou Metro Shield Segment as the research object to study its antierosion performance and durability life under the action of multiple factors.In this paper,a 120-day erosion test under the action of single sulfate,chloride,sulfate and chloride,bending load,sulfate and chloride,hydrostatic pressure,sulfate and chloride are designed.The ultrasonic velocity test,sulfate ion and chloride ion concentration test are carried out.Based on the test data,the corrosion resistance of shield segment concrete under the action of multiple factors and the diffusion law of sulfate ion and chloride ion are analyzed,the diffusion model of sulfate ion and chloride ion is established,and based on it,the durability life of Xuzhou subway segment is predicted.The main research results are as follows:(1)In this test,the bending load and hydrostatic pressure loading device are designed,which can meet the test requirements of long-term stable loading,and the test device is simple,convenient,easy to handle,and can be reused.(2)In the first 60 days of erosion,the ultrasonic velocity of concrete segments increased with the increase of erosion time,and then decreased with the increase of erosion time.The sulfate corrosion resistance first increased and then decreased,while the corrosion effect of chloride on concrete is not obvious.The ultrasonic velocity increases with the increase of erosion time when sulfate is mixed with chloride salt.The sound velocity increases first and then decreases with the increase of erosion time when chloride salt is mixed with sulfate.Under the interaction of sulfate and chloride,chloride always inhibits the diffusion of sulfate,but sulfate only inhibits the diffusion of chloride in the early stage of erosion,and accelerates the diffusion of chloride in the late stage of erosion.With the increase of bending load and hydrostatic pressure,the ultrasonic velocity gradually decreases,and the sulfate resistance gradually weakens.(3)The concentration of sulfate ion and chloride ion increases with the increase of erosion time,and decreases with the increase of erosion depth.The diffusion speed of sulfate ion in shallow depth is obviously greater than that in deep depth,and the diffusion depth of sulfate ion is obviously shallower than that of chloride ion.With the increase of sulfate or chloride concentration,the concentration of sulfate ion or chloride ion in each erosion depth and erosion time decreases.Sulfates and chlorides interact to inhibit each other over a 120-day erosion cycle.With the increase of bending load and hydrostatic pressure,the sulfate ion and chloride ion concentrations in each erosion depth and erosion cycle increase.(4)There is a good power function relationship between the surface sulfate and chloride concentration and erosion time,and the fitting formula are Cs=(A+ku)tB.The average diffusion coefficient of sulfate and chloride ions has little relationship with bending load and hydrostatic pressure,but has a good power function relationship with erosion time,and the fitting formula are Dt=D1t-m;sulfate and chloride diffusion models are C(x,t)=(A+ku)tB[1-erf(?)].There are 192 figures,29 tables and 120 references in this paper.