Research On Quality Defects And Safety Evaluation Standard Of New-built High-speed Railway Tunnel Lining

China,as the country with the longest mileage in the world's high-speed railway,is far more than other countries in the number of tunnel engineering and the mileage of its operation.However,with the increasement of the number of tunnels,the various problems of defects are becoming more and more prominent,but most of the related studies are concerned about the problems of tunnel disease during the operation,and lack of attention to the defects of the new-built tunnel lining.Based on the defects of some tunnel in the western Guizhou section of Shanghai-Kunming passenger dedicated line,this paper makes a statistical analysis on the defects of the new-built high-speed railway tunnel lining and sums up the causes of the defects from both the mechanical mechanism and the statistics.Combined with the numerical simulation method,the structure safety is evaluated from three aspects,such as cavity,lining thickness,lining cracks and so on.The safety evaluation standard for some lining defects of high-speed railway tunnel is summarized and applied to analyze the defects.The main contents are as follows:(1)This paper makes a statistical analysis on the defect data of some newly built high-speed railway tunnels in the western Guizhou section of Shanghai-Kunming passenger dedicated line.According to the statistics of the distribution of various defects from different sections,different grade of surrounding rock and different length grades,it is found that the problem of tunnel defects is common,and the distribution and severity of the defects are closely related to the construction management,the quality control,and the conditions of the geological surrounding rock.(2)This paper analyzes the mechanism and causes of the common tunnel lining defects,and then summarizes the causes of the defects such as the cavity,the concrete leakiness,the lining crack,the construction joint and the the water leakage.(3)In view of the cavitation defects behind the lining,the safety coefficient which is calculated by numerical simulation is used as an index to evaluate the safety of the structure.The safety coefficient changes under the changes of the surrounding rock grade,the width and the length of the cavity are analyzed,and the corresponding safety evaluation standards are set up.(4)In view of the deficiency of lining thickness,a similar calculation method and evaluation index are used to analyze the change of safety coefficient of different position,width,length,thickness and different degree of surrounding rock,and the corresponding safety evaluation standard is established as above.(5)In view of the defects of the lining,considering the fracture problem,the article calculates both the cross-section strength and the crack tip stability of the lining structure,and obtains the change law of the safety coefficient of the different cracks position and depth.And the corresponding safety evaluation standard is established according to the relevant specifications and codes.