Study On Failure Mechanism Of Lining Structure Of Mountain Tunnel Caused By Dislocation Of Fault

In order to speed up China’s development from a transportation power to a transportation power,a large number of tunnel projects have been invested in transportation infrastructure.Limited by the terrain and route conditions,especially for mountain tunnel projects,it will inevitably cross faults and fracture zones.Because the fault area has the characteristics of frequent earthquakes,strong tectonic movement and complex and changeable geological conditions,the earthquake movement causes the dislocation of faults,resulting in irreversible serious damage such as passive deformation,distortion and dislocation of tunnel lining structure.At present,the understanding of the failure mechanism of mountain tunnel lining structure caused by active fault dislocation is not perfect,and the evolution mechanism of lining structure failure induced by active fault dislocation is not clear,resulting in the increasingly prominent seismic damage problem of tunnel structure passing through fault section.It is urgent to study the failure mechanism of mountain tunnel lining structure caused by active fault dislocation.On this basis,aiming at the key scientific problems of structural loss of tunnel engineering,this paper comprehensively adopts comprehensive research methods such as statistical induction,theoretical analysis,numerical calculation and simulation test,respectively from the mechanical response law of mountain tunnel lining caused by active fault dislocation,the structural failure evolution mechanism of mountain tunnel crossing active fault section Systematic research has been carried out on the crack evolution mechanism and damage evaluation of lining structure.The main work contents are as follows:(1)By means of data investigation,statistics and induction,this paper expounds the harmfulness of fault dislocation to mountain tunnel engineering,analyzes the correlation between fault dislocation and tunnel earthquake damage,analyzes the damage characteristics of tunnel structure crossing active fault section caused by fault dislocation,puts forward the damage mechanism and damage mode of tunnel structure caused by active fault dislocation,and summarizes and classifies the main factors affecting tunnel structure damage.(2)Based on the typical case of tunnel crossing fault,a three-dimensional refined numerical calculation model is established.Based on the data investigation and induction results,the influence of offset and inclination on the stress deformation of secondary lining is studied,the deformation characteristics and stress characteristics of tunnel lining under different working conditions are analyzed in detail,and the mechanical response law of tunnel lining structure caused by fault displacement is revealed.Combined with the orthogonal test,the sensitivity analysis of tunnel damage factors is carried out,the influence of fault inclination,seismic intensity and tunnel depth on tunnel damage is clarified,and the prediction of vertical displacement of tunnel damaged lining is carried out.(3)Considering that the extended finite element method can accurately reflect the generation and propagation of cracks,the extended finite element method is introduced to study the crack evolution mechanism of tunnels crossing faults.An improved displacement field function with additional discontinuous variables is introduced into the displacement mode function at the crack tip to improve the original extended finite element shape function.With the help of the secondary development of ABAQUS software,an improved extended finite element method is proposed.According to the output results,a quantitative relationship between the crack growth length and the crack state is established to truly simulate the crack growth law and the crack damage evolution process of tunnel lining.(4)Based on the above extended finite element simulation method and comprehensively considering the influence of fault inclination angle and dislocation distance,the numerical calculation model of tunnel lining failure propagation through active fault is established under the conditions of different inclination and dislocation distance,the crack initiation position of tunnel lining structure under different working conditions is analyzed,and the crack length and inclination propagation law of tunnel lining structure are studied,The crack development law and crack mechanism of tunnel lining structure are clarified,and the failure evolution mechanism of lining structure induced by dislocation of active fault is revealed.(5)The large-scale physical model test of damage evolution of tunnel lining structure under active fault dislocation is carried out,the deformation and stress evolution characteristics of tunnel lining structure during fault dislocation are monitored,the deformation development law of tunnel lining structure,the most unfavorable stress position and lining failure form are analyzed,and the damage evolution law and characteristics of tunnel lining structure passing through active fault are revealed,The damage failure mode of tunnel lining is established.The model test results and numerical calculation results verify and supplement each other,and further clarify the failure evolution mechanism of tunnel lining structure passing through active fault mountains.(6)The research on tunnel lining failure evaluation in fault section is carried out,the key factors affecting tunnel lining failure are determined,and the tunnel lining failure evaluation index system is established.The fuzzy comprehensive evaluation method is introduced to carry out the research on the damage evaluation of tunnel lining passing through fault section,and the quantitative comprehensive evaluation of the damage degree of tunnel lining passing through fault section is realized.The accuracy and applicability of the above method and model are verified by field engineering examples.At the same time,the corresponding fortification measures are put forward,and the fortification parameters of tunnel lining structure crossing fault section are analyzed and optimized by using the constructed calculation method of tunnel crack propagation and crack damage parameters.