Study On Tunnel Construction Technology Of Xueshanliang Fault Zone

Most of Southwest China is mountainous heavy hilly area.The mountain high slope is steep,the terrain and geology are very complex,and the seismic belt is frequently distributed in complex seismic activities,the folds and faults are extremely developed,the weak and broken strata are widely distributed.With the development of a large number of infrastructure construction,highway tunnels will be built in high altitude and complex geological areas,and the construction of tunnel through the soft broken zone has been a key and difficult problem in the tunnel engineering.During the tunnel construction process,excavation and surrounding rock support forms are unreasonable,and instability and landslides are easy to happen.In this paper,taking the snow mountain beam tunnel project as the research background,the finite element numerical simulation is used to analyze the advanced supporting technology and construction excavation method of the tunnel in the surrounding rock section of the fractured zone which is affected by the snow mountain fault through the tunnel.The main contents of this paper are as follows.(1)Based on the geological survey data of Xueshanliang Tunnel,this paper analyzes the strengthening effect of the advance double deck small tube pre-supports technology on the grade V broken surrounding rock.By setting up different models of different angles,lengths and diameter parameters,we optimize and analyze the supporting parameters of the advanced double deck small pipes in the surrounding rock section of the fractured zone of the tunnel.The optimized parameters are as follows: The angle of extrapolation is divided into two kinds: the value of the inner layer's external angle is 7 degrees,and the value of the outer entry angle is 45 degrees,the length is 4m,and the diameter of the pipe is 42 mm.(2)On the basis of the optimization of the parameters of the small catheters,four methods were adopted: step method,circular excavation,core soil method,CD method and CRD method.From the three aspects of displacement,stress state and plastic zone distribution of the surrounding rock of the fracture zone,the influence of different construction methods on the stability of the surrounding rock of the fracture zone were analyzed.(3)Combined with the monitoring data,the reliability and applicability of the surrounding rock deformation law of the broken zone in the process of four kinds of construction method simulation are verified and analyzed.It can be seen from the calculation results that the measured data of the vault displacement and the surrounding convergence displacement are all larger than the numerical simulation results,but the law of the change of the surrounding rock displacement in the K19+360 ~ K19+430 section of the tunnel can be seen,and the laws of the simulated settlement and the measured data are basically similar.