Research On Key Technologies Of Yangzong Tunnel Crossing Fault Fracture Zone

China’s topography is complex.In the process of tunnel engineering route planning,it is inevitable to encounter complex geological conditions such as fault fracture zone.The surrounding rock of fracture zone is discontinuous and broken,which is easy to induce landslides,large deformation and other disasters in the construction process,resulting in tunnel construction safety accidents and huge economic losses.Yangzong tunnel of Kunming-Shilin Expressway passes through several fault fracture zones.In order to pass through the fault fracture zone smoothly,this paper studies the key technology of Yangzong tunnel passing through the fault fracture zone by means of model test and numerical simulation.The main research contents and conclusions are as follows:(1)Through the indoor model test of tunnel crossing fault fracture zone,the stress-strain law of surrounding rock of tunnel crossing fault fracture zone is obtained,that is,the change of radial stress and surrounding rock displacement in each part of the tunnel at the fault is the largest,so the reasonable construction method should be selected in the fault zone and the advance support should be strengthened properly.(2)The variation of stress and strain of surrounding rock in different construction methods of tunnel passing through fracture zone is compared and analyzed.Relying on the broken zone section of Yangzong tunnel,the displacement,stress and plastic zone change law of surrounding rock in the construction process of different excavation methods are compared and analyzed,and the comparison relationship of the effect of each construction method in controlling surrounding rock deformation,stress release and disturbance to surrounding rock is obtained,that is,the middle wall method > ring excavation reserved core geotechnical method > bench method It is suggested that the excavation of Yangzong tunnel in the fault fracture zone should be based on the circular excavation with reserved core.(3)Through numerical simulation,the influence of different excavation footage(0.5m,1.0m and 1.5m)and different length of lower bench(5m,7m and 9m)on surrounding rock is explored.Finally,with the increase of excavation footage and length of lower bench,the free time of surrounding rock increases,the surrounding rock control effect becomes worse.(4)This paper explores the reinforcement effect of advance small pipe grouting on tunnel crossing fault fracture zone,and the influence law of different reinforcement ring thickness(0.5m,1.0m and 1.5m)and different ring grouting range(120 °,135 ° and 150 °)on the reinforcement effect of advance small pipe grouting in fault zone tunnel.Finally,with the increase of reinforcement ring thickness,the settlement of tunnel vault is obviously controlled With the increase of the annular grouting range,the convergence around the tunnel is obviously controlled.