Study On Multi Factor Directional Corrosion Effect And Performance Degradation Law Of Tunnel Concrete

Rock tunnel is widely existed in every area of our country,which is a great contribution to the crossing obstacle,shortening the mileage and easing traffic pressure,but the durability of rock tunnel is becoming more and more serious.Durability of concrete in tunnel is the largest sulfate corrosion,chloride and sulfate also exist at the same time the interaction in the vast majority of environmental water,two factors?compound effect of sulfate and chloride?erosion effect of rock tunnel lining under corrosive environment and tunnel in soft soil in the same environment erosion effect is obviously different,and the single factor?chlorine salt and sulphate alone?and erosion effect of tunnel lining under corrosive environment are quite different.Based on the actual situation of tunnel environment,this paper considers the effect of unidirectional erosion and the degradation law of concrete under the coupling action of various factors.This paper focuses on the research of concrete single direction semi immersion corrosion in natural environment corrosion,considering different corrosive environment,namely Na2SO4 solution?the concentration of 5%,10%?and NaCl solution?the concentration of 5%,10%?between the portfolio and the carbonation environment,analysis of various factors for corrosion of reinforced concrete tunnel under degradation the law,and analyze the causes of degradation.?1?The corrosion of pure Na₂SO₄ solution with NaCl and Na2SO4 mixed solution in the environment of concrete test block for ultrasonic velocity measurement,using the formula to calculate the thickness of corrosion layer specimen were used to evaluate the concrete,chloride on the inhibition of sulfate corrosion of concrete.The experimental results show that: through observation and comparison on the change of corrosion layer thickness and morphology,have confirmed the existence of Cl-inhibited the proliferation rate of SO₄^2-,and with the increase of Cl-concentration the inhibitory effect has a certain degree of reinforcement.?2?To study the influence of carbonation on the diffusion of SO₄^2-in the two factors corrosion concrete,and the variation of the mechanical properties and durability of concrete under multi factor conditions.The concentration of each concrete one-way erosion depth SO₄^2-,the diffusion of SO₄^2-in concrete,and the influence of different concentrations of Cl-on the condition of SO₄^2-diffusion,to further explore the corrosion factors of concrete underthe condition of SO₄^2-.The results show that the carbonation promotes the diffusion speed of SO₄^2-,increased the corrosion degree of concrete;multiple factors(Cl-,SO₄^2-,carbide)corrosion effect on concrete carbonation,the main role,Cl-inhibition of coupling complex still needs further research.?3?Study on the corrosion of steel in concrete under the coupling action of chloride and sulfate,the tensile strength of the steel bar,and the corrosion rate of the steel bar are studied.The results show that the existence of SO₄^2-can reduce the corrosion of steel bar and the tensile strength of Cl-.