Research On Safe Construction Technology Of Zhongliangshan Tunnel

In recent years,although the construction of high-speed railway tunnel has greatly improved the rail transit line and improved people’s travel efficiency,it has also brought many security risks,which will not only cause great economic losses.In this case,people pay much attention to the safety of tunnel construction.Therefore,it is of great significance to study the safety of tunnel construction.In this thesis,the slope of the entrance section of Zhongliangshan high-speed railway tunnel is simulated and analyzed,and the mechanical analysis of the anchor cable frame beam under different conditions is carried out by using the numerical simulation method,and combined with the numerical simulation results,the best support scheme is given.At the same time,in order to ensure the safety of tunnel construction and find the optimal construction effect,this thesis uses the numerical simulation method to compare the five different construction schemes.This method can provide some technical basis for the structural optimization design of this type of tunnel.The main work and results of this thesis are as follows:（1）Considering the important role of slope stability of mountain tunnel entrance in the whole process of tunnel construction and operation,combined with the slope of Zhongliangshan high-speed railway tunnel,the basic situation of the slope is analyzed;The bad geological characteristics of this area are summarized,and the analysis and research of slope stability and underground engineering stability should be strengthened.（2）According to the actual construction of Zhongliangshan high-speed railway tunnel,the numerical simulation and analysis of the original slope reinforcement and slope reinforcement construction under three different working conditions prove that the safe operation of the slope and the stability of the mountain are effective after the support;In the process of slope excavation by layers,the closer the slope is to the mountainside,the greater the deformation increment of the slope and the greater the bending moment increment of the frame beam.Therefore,in the actual reinforcement,the stability of the slope can be further improved by adding prestress to the upper part of the adjacent hole or increasing the section area of the frame beam.（3）Lizheng geotechnical software was used to analyze the influence of the construction of Zhongliangshan high-speed railway tunnel on the stability of the slope at the top of the tunnel.It was found that the main deformation mode of the slope was shear deformation.When the slope was unstable,the slope sliding surface would slip out under the action of shear stress.At the same time,for this kind of slope instability problem,it is suggested to adopt the most effective support method is slope cutting,prestressed bolt beam support.（4）In view of the water enrichment,large deformation and instability of surrounding rock during the excavation of Zhongliangshan high-speed railway tunnel,the following construction scheme is proposed through theoretical research and field tests:when the water inflow inside the tunnel is small,the tunnel is directly excavated by force,and the drainage hole is set on the inside of the tunnel face to reduce the internal water pressure,and then the tunnel is directly carried through with water.The design of this scheme is as follows:when the water inflow of the single hole of the drain hole on the inside of the tunnel is less than 40 m³·h^-1and the total water inflow is less than 300 m³·h^-1,the construction scheme of all grouting reinforcement around the tunnel is adopted;when the total water inflow of the drain hole on the inside of the tunnel is more than 300 m³·h^-1,the construction scheme of full section curtain grouting is adopted.（5）In order to ensure the safety of tunnel construction and seek the best construction results,the five construction schemes proposed in this tunnel were studied and compared through numerical simulation:as the scope of grouting reinforcement gradually increased,the vault subsidence,arch bottom uplift and horizontal convergence displacement values of the arch belt of the tunnel all showed a trend of rapid decline and then gradually stable change.By analyzing the final value of the displacement around the tunnel and the maximum extrusion deformation of the face of the tunnel,it can be concluded that the full section curtain grouting can reduce the displacement most obviously.By analyzing the monitoring line of pore water pressure and the changes of water inflow in the tunnel under different working conditions,it can also be concluded that the method of full-section curtain grouting is the best choice.The application of this scheme has brought safety and economic benefits.