Analysis Of The Mechanical Mechanism And The Effect Of Pipe Roof Advanced Support In Tunnels

The distribution of tunnels in China is wide.The terrain and geological conditions of the tunnels are complex and changeable.In the process of the construction,due to the influence of various factors,if the surrounding rock has poor self-bearing capacity,it is very easy for the surrounding rock to become unstable.When the support is not timely,or the design strength of the support is not enough,the tunnel collapse will also occur,which will cause the construction accident.In this way,the construction cannot be carried out normally,thus delaying the construction period and affecting the quality of the project.Meanwhile,the life safety of the construction personnel is not guaranteed.In order to improve the stability of the surrounding rock in the process of the construction,we need to adopt special reinforcement method to advance the working face and the surrounding rock,so as to improve its stability.Preliminary support of the pipe roof is before the tunnel excavation on surrounding rock pre-reinforcement,its formation mechanism is the square in front of the excavation,the cross section along the tunnel set an arch shell structure,form a system of preliminary support,thus stable formation,makes excavation surface and its surrounding rock reinforcement,guarantee the tunnel construction in a relatively stable environment.Through theoretical analysis and numerical simulation,this paper makes further research on the pipe roof.The main research contents and results are as follows:1.In view of the tunnel advance protection technology,several types of the techniques are systematically summarized,and the preset protection technology of the pipe roof is described in detail.2.According to the damage characteristics of surrounding rock,several situations of brittle damage and plastic damage are summarized.At the same time,the factors affecting the stability of the tunnel are analyzed.In addition,the limit equilibrium method of tunnel stability analysis is described.3.This paper makes a systematic summary of several commonly used theory of the surrounding rock pressure.According to the characteristics of the pipe roof support,and the burial depth of the tunnels,put forward the deep and shallow buried tunnel pipe roof formula of the stress,and points out Influence range and distribution form of the pipe roof,the mechanical model of pipe roof was established,and the subsidence,rotation and bending moment of the pipe roof were obtained.4.Through the establishment of the three-dimensional finite element model,the calculation results are analyzed,the internal force distribution of the pipe roof,the deformation of surrounding rock in the tunnel and the subsidence curve of the pipe roof are obtained.5.The three influencing factors of pipe diameter,spacing and length of pipe roof are analyzed,and based on the finite element model of the same parameters under different conditions were calculated,the influence degree of each parameter is obtained by comparing the internal force of the pipe roof,the vertical displacement of surrounding rock and the horizontal clearance convergence in the tunnel.And finally,the parameters of the pipe roof are optimized by economy and efficiency.