Study On Sulphate Corrosion Characteristics And Life Evaluation Of Tunnel Sprayed Shotcrete

Shotcrete is widely used in civil engineering fields such as foundation pit engineering.tunnel engineering and mine engineering Due to its advantages of simple technology and flexibility.In view of the construction characteristics of shotcrete,it is directly related to the surrounding medium of engineering structures in general,shotcrete is the first line of defense for engineering support or protection,affected by underground water prominently.Sulphate is widely distributed in China,the problem of durability deterioration of concrete structures caused by sulfate corrosion is very prominent.A lot of achievements have been made in the research of corrosion characteristics and service life of concrete poured under sulfate attack at present,however,the research on the corrosion behavior of shotcrete materials is not perfect.Therefore,it is of great engineering significance to study the corrosion characteristics of shotcrete and evaluate its service life under sulfate attack.Due to the different construction technology,there is a significant difference between shotcrete and concrete structure.Firstly,this article consults relevant literature,the general situation of sulfate corrosion on tunnels,the forms and types of corrosion diseases are summarized,determine the research methods of laboratory test.on this foundation,the influence of the concentration of corrosive solution on the physical and mechanical properties of shotcrete is analyzed,five physical properties including appearance,mass,compressive strength,relative dynamic modulus of elasticity and damage thickness are obtained.To analyze the erosion mechanism,revealing the law of damage evolution,adopting SEM microcosmic test method,evolution process of corrosion products,internal crack development and interfacial damage of shotcrete under sulfate attack are obtained.The research results show that the change of microstructures is the fundamental reason for the deterioration of physical properties.Final,taking relative dynamic modulus of elasticity as damage Variable of Shotcrete,the damage evolution equation is used to predict the service life of shotcrete.The main research contents are divided into the following aspects:Firstly,Experiments on physical and mechanical properties are carried out.the variation of 5 physical properties of shotcrete under different solution concentration is obtained,five physical properties of shotcrete and cast-in-place concrete with different construction technology and same concentration are obtained and compared.Secondly,By Carrying out SEM microscopic test,the evolution process of the internal microstructure of shotcrete under different erosion concentration is obtained,the evolution process of internal microstructures of shotcrete and cast-in-place concrete with different construction technology and same concentration was obtained,it is explained that the change of micro-structure is the fundamental reason for the deterioration of macro-performance.Thirdly,By establishing damage evolution equation,analysing damage parameters and Regularity of Concrete,verifying the Correctness and Rationality of Damage Evolution Equation and predicting the service life by Damage Evolution Equation,providing reference opinions for service life prediction of practical projects.