| In order to study the construction mechanics effect of the No.1 gas transmission tunnel in the D-line project of the Central Asia Natural Gas Pipeline,this paper adopts numerical simulation and on-site monitoring for the characteristics that the surrounding rock of this tunnel is mostly mudstone and argillaceous limestone and the tunnel section is relatively small.The method of combining measurement and measurement has studied the construction mechanical effect of the tunnel.The main research contents and conclusions are as follows:(1)According to the characteristics of medium section and poor surrounding rock conditions of No.1 gas transmission tunnel in Tazhong,the construction stability of the tunnel under two excavation methods such as full section method and step method was simulated by numerical simulation method Through the comprehensive comparison and analysis of the surrounding rock deformation,the stress of the spray-mixed structure,the stress of the anchor structure,and the range of the plastic zone of the surrounding rock under different excavation methods,it is recommended to use the step method for the construction of the No.1 gas transmission tunnel in Tazhong.(2)The numerical simulation method was used to simulate the construction stability of the No.1 gas transmission tunnel in Tazhong under three different step lengths of 4m,8m,and 12 m.Based on the numerical simulation results,the lower wall of different step lengths Comprehensive comparison and analysis of rock deformation,stress of spray-mixed structure,stress of anchor structure,range of surrounding rock plastic zone,etc.It is recommended that the step length of No.1 gas transmission tunnel in Tazhong be 4m.(3)Using the method of numerical simulation,the vertical and horizontal deformation characteristics of surrounding rock at the variable cross-section of Tazhong Gas Transmission Tunnel No.1 and the stress variation characteristics of surrounding rock,the stress forms of spray-mixing and anchor structure,and ordinary sections and The difference in the distribution of the plastic zone of the surrounding rock in the widened section.On this basis,the construction stability characteristics of the surrounding rock and supporting structure at the variable section of the No.1 gas transmission tunnel in Tazhong are summarized,and relevant construction suggestions are proposed.(4)A monitoring and measurement program was developed to monitor the deformation of surrounding rock,the pressure of surrounding rock and the internal force of the steel arch during the construction of No.1 Gas Transmission Tunnel in Tazhong.Based on the monitoring and measurement data,the variation law of surrounding rock deformation,surrounding rock stress and axial force of the steel arch is analyzed,and the monitoring results and numerical simulation results are compared and analyzed to verify the rationality of the adopted construction scheme.Through the above research,we have an in-depth understanding of the optimization of the construction method of the soft rock gas transmission tunnel and the stress and deformation characteristics of the surrounding rock and supporting structure of the variable cross-section section,which has certain reference significance for similar projects in the future. |
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