Three-dimensional Mechanical Response Of Tunnel Surrounding Rock Excavation Under The Control Of Fault Fracture Zone

At present,with the rapid development of transportation infrastructure,the number of highway bridges and tunnels in China is increasing,and the bad geology encountered during construction is becoming more and more complicated,especially in the process of tunnel construction,where faults Some bad geological layers such as broken zone have an important impact on the safety of tunnel construction.Due to its complicated geological origin and physical and mechanical characteristics,fault broken zone is extremely easy to cause safety accidents during the excavation process.The deformation law of tunnel surrounding rock is of great significance to guide construction.In this paper,the method of combining physical model test and coupled numerical simulation is used to explore the impact of fault fracture zone and its factors on tunnel excavation.The main contents and conclusions of the study are as follows:(1)The stability of the surrounding rock under the fault-bearing fracture zone and its impact on the construction are studied,the necessity of the study is illustrated,and in combination with the currently commonly used research methods,the current status of the research is summarized through comparison;(2)According to the similarity theory,taking the surrounding rock of the V-level fault-bearing fracture zone as the research object,the similar materials and proportions of the model test are determined through indoor experiments,using the self-designed model test box,combined with the currently popular digital speckle photographing technology Test methods such as pressure sensors and pressure sensors,physical model tests of tunnel excavation with fault fracture zones were carried out,and the data collected by the test were analyzed to obtain the deformation law of surrounding rock and stress monitoring results during the excavation process.During the tunnel excavation process,There are three typical changes in the stress near the palm face,the stress concentration zone,the weak stress concentration period in the front,and the rear stress release zone;for the displacement near the palm face,there are also extrusion deformation,pre-displacement,and post-displacement 3 Characteristics of time and space evolution,which correspond to changes in stress;(3)According to the continuous-discrete calculation principle and their respective advantages,a multi-scale coupling simulation method based on continuous-discrete is proposed,and the feasibility and rationality of the coupling are analyzed using FLAC3 D and PFC3 D programs as the implementation platform;Hoek-Brown strength criterion is used as the continuum constitutive model,and the linear parallel bonding model is selected as the discrete element model;(4)Through numerical simulation,comparative analysis of the model test results,the rules are basically the same as the model tests,further analysis of the deformation of the surrounding rock during tunnel excavation and the process of crossing the fault fracture zone shows that the fault fracture zone opened the tunnel The effect of excavation and the discontinuous features above and below the fault fracture zone,through digital speckle technology,the whole field strain and displacement of the surrounding rock during the excavation process are obtained,and the distribution characteristics are analyzed;(5)Based on the multi-scale coupling calculation method,the different factors of the impact of the fault fracture zone on the tunnel excavation are explored,and the deformation law of the tunnel excavation under the change of the inclination,tendency and width of the fault fracture zone is studied;Multi-scale coupling calculation method,established a numerical coupling model under different variables,and summarized the results of tunnel excavation under different inclination angles,inclination and widths of the fault fracture zone.Among them,under different inclination angles and inclination,the approximate distribution is 30?and 150?,it has a greater impact on tunnel excavation,and at 90?,it is the smallest.When the width of the fault fracture zone changes,the wider the fault fracture zone,the greater the impact,but the overall impact trend is slower.Based on the research of the above regularity,we can provide guidance suggestions for the actual project when encountering the fault fracture zone.When encountering the fault fracture zone,we can clearly know the stress distribution characteristics and surrounding rock deformation of the surrounding rock during the excavation process.,So as to adopt effective supporting measures to avoid construction accidents.