Study On Deformation Characteristics And Stability Of Soft Rock Tunnel In Coal Series

This thesis relies on the project to build a Gaopo Tunnel from the Chengdu to Guiyang high-speed railway.Through theoretical analysis,in site monitoring measurement and numerical analysis,the mechanism of large deformation in the coal series replacement section of the Gaopo Tunnel is compared.Based on the above research,the safety deformation of the Gaopo Tunnel under the new support scheme is analyzed.Based on the above research,and the control technology of the large deformation of the weak surrounding rock of the tunnel is discussed.The thesis specifically carried out as following:(1)Relevant literature on large-scale deformation of soft rock in the tunnel is consulted,and existing research on large-scale deformation of soft rock in the tunnel,theoretical calculation method of surrounding rock pressure,and deformation mechanism of layered surrounding rock and control technology of soft rock deformation in large-scale tunnel is analyzed.The deformation and damage of the surrounding rock and supporting structure is revealed by the preliminary data of the survey data and on-site construction.And tunnel construction methods,structural parameters of the old and new supporting schemes,and the existing tunnel deformation characteristics are collected.The deformation and failure mechanism,large deformation level and failure characteristics of Gaopo Tunnel under the initial support scheme are qualitative analyzed.(2)Combined with the new support plan,the on-site monitoring and measurement plan for the test section of Gaopo Tunnel is determined.The monitoring items include surrounding rock stress,steel frame stress,concrete stress,bolt axial force,internal rock displacement,and secondary lining reinforcement stress.Based on the monitoring data of the project,the timehistory curve of the monitoring data of each project,and the spatial distribution map of the cross-section are acquired,after the monitoring data of each project is stable.This is used as an important basis for analyzing the stress and deformation of the tunnel during the disassembly and replacement of the coal series deformation section of the Gaopo Tunnel.(3)The finite element software Abaqus is used to numerically analyze Gaopo Tunnel.First,the main differences between the front and back of the tunnel are sorted out to determine the different working conditions in the two-dimensional numerical analysis.Rock displacement and plastic zone distribution,initial support stress changes also can be established;Secondly,the finite element software Abaqus is used to establish a three-dimensional model to simulate the stress and deformation of the surrounding rock and support structure with tunnel excavation under actual stress conditions and geological conditions.The numerical results about the surrounding rock displacement,initial supporting structure stress,steel frame stress,bolt axial force and secondary lining stress and deformation stabilized are extracted under the target crosssection,and the numerical simulation results will be changed with the same type of monitoring items.Compare and analyze with the stabilized monitoring data,and then comprehensively analyze and evaluate the safety and stability of the tunnel under the current support scheme.(4)Combining the field monitoring data and numerical simulation results of the tunnel and the deformation of the surrounding rock and supporting structure exposed during the tunnel construction,the principle of large deformation control of the weak surrounding rock tunnel is proposed,and the deformation control technology of the deformation section of Gaopo Tunnel is analyzed and summarized.