Study On Optimization Of Design Parameters Of Lining Crack Regulation In Xiaoshizi-Jiaochangkou Section Of Metro Line 1

Nowadays,the construction scale of urban subway is expanding day by day,the lining structure of subway tunnel will also appear all kinds of diseases under the natural or man-made action,the most harmful is the lining cracks,so it is very necessary to strengthen the subway tunnel with cracks.At present,scholars have carried out a lot of research on the reinforcement of cracked lining,but there are few studies on the influence of steel belt and steel arch parameters on the reinforcement effect of lining,so it is necessary to deepen and improve the research in this aspect.In this thesis,the lining crack rectification project of Xiaoshizi-Jiaochangkou section of Metro Line 1 is taken as the research background.According to the disease condition,the reinforcement object is determined to be the longitudinal crack of the arch,and the method of attaching steel belt and adding steel arch frame is adopted to strengthen the lining.Through the establishment of finite element numerical model,the influence of the parameters of steel belt and steel arch on the reinforcement effect of crack lining is studied,and the final results are analyzed and summarized.The main research contents and conclusions of this thesis are as follows:（1）The classification criteria of lining cracks according to the width,length and depth of cracks and the propagation mechanism of single and compound cracks are summarized.The causes of lining cracks are summarized.（2）The fracture stability factor k is proposed as the safety evaluation criterion of the cracked lining structure.Taking crack as the research object,the relationship between stress intensity factor K and its critical value K_IC in the basic theory of fracture mechanics is analyzed.It is shown that the crack begins to expand when the stress intensity factor K reaches its critical value K_IC.Based on this,a coefficient K reflecting the relationship between k and K_IC is proposed to determine whether the crack expands.（3）The effects of the width,thickness and longitudinal spacing of the steel strip on the reinforcement of the split lining were studied,and the optimum reinforcement parameters of the steel strip were determined.The three dimensional numerical simulation of steel strip reinforced crack lining with different widths,thicknesses and longitudinal spacing was carried out by the finite element numerical simulation software ANSYS.The optimal reinforcement parameters were obtained by analyzing and comparing the crack stress intensity factor and crack stability factor k.Based on the principle of orthogonal design,the sensitivity of reinforcement parameters is analyzed,and the law of reinforcement effect of steel strip with each reinforcement parameter is obtained.The analysis results show that different parameters have different influence on the reinforcement effect of lining.（4）The influence of the type of steel arch and the spacing of longitudinal arrangement on the reinforcement of the lining with cracks is studied and the optimum reinforcement parameters of steel arch are determined.The three dimensional numerical simulation of steel arch reinforcement with crack lining with different types and longitudinal layout spacing was carried out respectively.The law of reinforcement effect of steel arch with different parameters was obtained by analyzing and comparing the crack stress intensity factor and crack stability coefficient k,and the optimal reinforcement parameters were obtained.The best reinforcement method is obtained by comparing the reinforcement effect of steel belt and steel arch with the best parameter combination.