Analysis Of The Structural Reliability Of Highway Tunnels Based On The Limit State Method

With the rapid development of China’s highways,the number of highway tunnels is also increasing.As most highway tunnels are located in a more complex rock environment and the mechanical relationships are not clear,the traditional way of safety evaluation of tunnels,i.e.the coefficient of safety method,cannot take into account the variability of the tunnel structure parameters and the probability of the tunnel structure completing its intended function under certain conditions,in the analysis process,the theoretical method of The choice of the theoretical method is crucial for the safety analysis results of the tunnel structure.The reliability analysis research based on the limit state method is the mainstream trend in the current development of tunnel structure design and safety evaluation.This paper starts from the working mechanism of the highway tunnel support structure,takes the actual highway tunnel as the research background,based on the principle of limit state method,and carries out reliability analysis research on the highway tunnel structure.The main research elements are as follows.(1)This paper provides a detailed introduction to the background of the actual motorway tunnel project selected,summarises and collates the basic principles of reliability analysis,compares and contrasts the current analysis methods for structural reliability,and selects a reliability analysis method that is scientific and applicable to the content of this research paper,namely the Monte Carlo method.(2)Based on the basic principles of the stratigraphic structure method,reasonable parameters of the tunnel structure were selected with reference to actual engineering data and specifications,and a tunnel structure calculation model was constructed using ANSYS software.The mechanical state and deformation of the tunnel structure were investigated.The reliability of the selected tunnel entity as the object of reliability study and the applicability of the tunnel structure parameters were verified.(3)Based on the limit state method to analyse the principle and process of constructing the limit state equation,choose to establish the structural limit state equation with the ultimate displacement of the support structure,based on the PDS technique,carry out reliability analysis on the shotcrete structure and secondary lining in the initial support of the tunnel,select reasonable random variables as the input variables that may affect the reliability of the tunnel,adopt the principle of Monte Carlo method to carry out statistical analysis on its 5000 times sampling probability,ensure the sample size is sufficient by studying the statistical characteristics of the input variables,and ensure the reliability analysis results have accuracy and applicability.(4)The reliability analysis of the shotcrete and secondary lining structures of the highway tunnel was carried out,combining the limit state equations to derive their structural reliability and probability of failure,in which the reliability of the shotcrete structure is low and the probability of failure is high;the reliability of the secondary lining structure meets the structural safety requirements.Afterwards,sensitivity and linear correlation analyses of the parameters of the shotcrete and secondary lining structures were carried out to derive the influence of the support structure parameters on the reliability,and based on the analysis results,targeted reinforcement of the shotcrete structure was carried out,and the reliability of the sprayed mixed structure after reinforcement was compared and analysed to verify the reinforcement effect and provide reference for the actual project.