Research On The Influence Of The Cracking Of The Secondary Lining Of Existing Railway Tunnel On The Structural Performance And Prevention Measures

The 2020 China Tunnel and Underground Engineering Conference（CTUC）specifically put forward several concepts such as the life cycle cost of operating tunnels,the convenience of existing tunnel maintenance,and the standardized construction of maintenance and reinforcement technology.All kinds of signs show that China’s tunnel development has entered the stage of"construction,management and maintenance",and a large number of tunnels have entered the maintenance cycle.However,in the evaluation system of the health status of railway tunnels in operation,there is still a lack of quantitative research on the judgment standard of some disease factors and the change of comprehensive health value of tunnels under the action of various diseases.For this reason,this paper first establishes the fuzzy comprehensive evaluation model of existing railway tunnel disease diagnosis to quantitatively analyze the overall health status of the tunnel,secondly,relying on the background of secondary lining cracking disease of songshuwan tunnel,use ANSYS software to establish a finite element model of the structure with cracks,the influence mechanism of different cracking modes on the secondary lining structure performance of existing railway tunnel is analyzed,and the safety evaluation results of the cracked secondary lining structure under various working conditions are sorted,finally,prevention and control measures are proposed for different degrees of tunnel secondary lining cracking diseases according to the principle of reinforcement and reinforcement.The main research contents are as follows:（1）List five evaluation indicators that affect railway tunnel diseases:lining cracks,leakage,lining material deterioration,cavity behind lining,lining spalling characteristics,cause mechanism and judgment criteria,provide a basis for the quantification of disease factor parameters.（2）Introduce the membership function of fuzzy mathematics to quantify the judgment results of each index factor according to the judgment criteria,a multi-level fuzzy comprehensive evaluation model based on analytic hierarchy process（AHP）is established for the comprehensive evaluation system of existing railway tunnel disease diagnosis,and substitute it into the calculation example data The relative error of the trial calculation results is less than 20%,which verifies the feasibility of the comprehensive evaluation system.（3）Since the criterion for crack stability of the second lining cracking disease judgment standard is not perfect,the safety factor（K₁）of crack tip stability and the safety factor（K₂）of section bearing capacity are introduced to establish the secondary lining structure with cracks.Study the mechanics response law of the secondary lining structure under different cracking positions and crack depth combined working conditions,analyze the influence mechanism of different cracking modes on the performance of the secondary lining structure of the existing railway tunnel.Explores the comprehensive safety evaluation results of the secondary lining structure with cracks based on the crack stability and bearing capacity safety factor.（4）On the basis of the existing tunnel cracking treatment,combined with the safety evaluation results of the cracking secondary lining structure under various working conditions,according to the principle of reinforcement and reinforcement,the optimization suggestions and treatment measures for different types of secondary lining cracking diseases are proposed.