Study On Deformation Characteristics And Stability Evaluation Of Surrounding Rock Of Subway Tunnel Passing Through Fault Zone

When subway tunnel passes through the fault fracture zone,it will face extremely complex engineering geological conditions,especially in the influence range of the fault fracture zone.After the excavation of the tunnel,it will cause disturbance to the stratum.The existence of the fault fracture zone will greatly affect the earth stress rebalance and the stability of the surrounding rock of the tunnel.Based on the elastic-plastic mechanics analysis,the paper analyzes the surrounding rock stability of the subway tunnel passing through the fault fracture zone by means of numerical simulation and grey correlation method,and puts forward the evaluation index of the surrounding rock stability from the mechanical point of view to further study the influence of the fault fracture zone on the surrounding rock stability.The main research work and achievements are as follows:(1)This paper discusses the change of stress state of surrounding rock caused by tunnel excavation,analyzes the redistribution stress characteristics of surrounding rock after excavation by using the elastic-plastic theory,and further analyzes the distribution law of stress and strain of surrounding rock after excavation,on the basis of which,the deformation state division of surrounding rock after excavation is obtained,the failure range of surrounding rock is determined,and the failure characteristics and criteria of surrounding rock are analyzed.(2)Based on the analysis of elastic-plastic theory,this paper analyzes the factors that affect the deformation of surrounding rock of tunnel by using the grey correlation theory,mainly considering the influence of the properties of rock and soil,the strength of tunnel support structure and other factors.Firstly,the dependent variable sequence and independent variable sequence of the grey correlation model are determined,and the correlation degree is obtained by using the calculation of MIDAS GTS NX geotechnical finite element software and MATLAB programming.The quantitative analysis is made on the influencing factors of the stability of the surrounding rock of the tunnel.The calculation results show that the influence of the strength of the support structure on the deformation of the surrounding rock of the tunnel is greater than that of the rock and soil.(3)The FLAC3 D software is used to model and calculate the subway tunnel passing through the fault fracture zone,and the stress-strain law and failure characteristics of surrounding rock after excavation are analyzed.At the same time,on the basis of the first two parts of the work,set up a control test for calculation.The control group mainly considers the situation of not affected by the fault fracture zone and the surrounding rock without support after the excavation of the tunnel,and analyzes the influence of the fault fracture zone and support effect on the stability of the surrounding rock of the tunnel.The research shows that along the axis of the tunnel,the stress-strain distribution of the surrounding rock changes greatly within the influence range of the fault fracture zone.In this range,the stress-strain of the surrounding rock is greater than that of other areas,the development degree of the plastic deformation of the surrounding rock is greater,and the existence of the support effect has an important impact on the stability of the surrounding rock.(4)Based on the research of the first three parts and the analysis of elastoplastic mechanics,the evaluation index of the stability of the surrounding rock of the tunnel is put forward to evaluate the stability of the surrounding rock of the subway tunnel passing through the fault fracture zone.By means of numerical simulation,the evaluation index of tunnel surrounding rock stability based on the mechanism of surrounding rock failure mechanics is calculated and analyzed considering the special geological conditions of fault fracture zone and the role of support structure in construction factors.The analysis shows that the evaluation index can effectively evaluate the stability of tunnel surrounding rock after excavation and evaluate the influence of fault fracture zone and the supporting effect Effect.