Research On Large Deformation Control Technology Of Single-track Railway Tunnel In High-intensity Zone

Reliance on the Lixiang single-track railway tunnel under construction through the Tethyan-Himalayan fault system,The region has complex geological structures,strong neotectonic movements,large-scale active faults,dense distribution,frequent seismic activities,large magnitude,long earthquake rupture belts,large displacements,and ground acceleration peak acceleration of 0.2 g,it is a high intrnsity area.The tunnel has the characteristics of high intensity area surrounding rock crushing,low strength of surrounding rock,high water permeability,high geo-stress and development of joint and fissures.In the early stage of large-scale deformation of soft rock in high-intensity tunnels,not only the absolute magnitude is large,but also the displacement speed is very fast.In order to effectively control the large-scale deformation of soft rock tunnels in high-intensity areas,safety accidents during the construction of tunnels are prevented.In this paper,field surveys,field tests and numerical simulations are used to optimize the tunnel section types,and the factors affecting the stability of the single-track soft tunnels in high-intensity areas and the control techniques are summarized.The main work is as follows:(1)From the angle of the secondary lining safety and the deformation of the initial support structure,the 3 major deformation sections after the original design section and the optimized design are compared and analyzed.The horizontal deformation is the main factor of the single track railway tunnel,and the horizontal convergence of the wall waist and the wal waist decreases with the increase of the sectional curvature.(2)The influence of the lateral pressure coefficient,the ratio of strength to stress of the surrounding rock,and the angle between the maximum principal stress and the tunnel axis was investigated to investigate the influence of the stability of the soft rock tunnel on the single-track railway.The tunnel deformation increases with the increase of the lateral pressure coefficient,and increases with the smaller ratio of strength to stress of the surrounding rock.The tunnel axis should intersect with the maximum principal stress as small as possible.(3)When bolting in weak surrounding rock tunnels,improper design of bolt support will not only waste time and money,but also adversely affect the stability of the tunnel.With the model of large deformation IIA section and lateral pressure coefficient λ=1.5,t the optimization scheme of bolting for single track railway soft rock tunnel is put forward from the angle of design length and placement of anchor rod.4.5 m anchors applied to the upper stage,6.5 m anchors applied to the middle stage and no anchor applied to the bottle stage.(4)A three-dimensional numerical model is established to simulate the construction process,and the safety of step method is verified.The reasonable construction method of single line railway soft rock tunnel are studied.Through what comparison analysis of the lower step alone excavation and the lower step and the instep once excavation,the lower step and the instep arch excavation one step,the difference in the length of the middle step,when the closing distance is the same,the difference in the length of the upper step,the same length of the upper step closed distance.In the aspect of the upper stage and middle stage short,it is easier to control the deformation with excavation of bottle stage and inverted arch,longer length of upper stage and bench construction with timely support.(5)In order to verify the reliability and safety of the numerical simulation results,through the collection of on-site data and the installation of the instrument,the corresponding section of the test section was monitored and tested,and the numerical simulation was verified to conclude the safety and reliability of the test.Safe construction.