| In the project of expanding the existing flat guide tunnel into a railway tunnel,the design is usually calculated according to the new tunnel.In fact,after the completion of the long-term stress adjustment of the flat-conducting hole,it has reached a relatively stable state,and the excavation process will cause secondary disturbance to the surrounding rock,and the stress will be redistributed,thus affecting the stability of the surrounding rock..This paper aims to explore the influence of the expansion of the horizontal tunnel on the stability of the surrounding rock.Based on the analysis of the related data and the long-term monitoring and measurement of the tunnel,this paper discusses the process of expanding the tunnel into the tunnel through the positive tunnel of the Xinshan Shutuo Tunnel.The impact of stability.The paper uses Midas GTS NX software to analyze the influence of construction method and excavation footage on the stability of surrounding rock in different grades.The influence mechanism of the expansion of Pingding Tunnel on the stability of surrounding rock is studied.The safety of the tunnels built by different methods was analyzed for strength reduction,and the differences in the influence of different construction methods on the surrounding rock were obtained.The main research contents of this paper are:In this paper,the finite element limit analysis method is used as the evaluation method of surrounding rock stability.The criterion of instability failure of finite element model,the calculation method of structural safety factor and the quantification method of self-bearing capacity of surrounding rock are established to ensure the scientific conclusion of the paper.accurate.2 This paper uses the theory of surrounding rock stress field to explain the influence mechanism of the expansion of the flat tunnel on the stability of the surrounding rock.Combined with the engineering monitoring data,the damage form of the deep buried railway tunnel in the homogeneous rock mass is analyzed and judged.It is known that the overall failure mode of the tunnel structure is tensile cracking and shear composite failure.3 Through the numerical simulation analysis of the construction process of single blasting and excavation leveling tunnel,the influence law of excavation footage and construction method on the stability of surrounding rock during construction is obtained.The optimal excavation footage of the V-class surrounding rock condition is determined to be 1 m,and the conclusion that the excavation is more unstable than the full-section excavation is obtained.4 Through the numerical simulation analysis of the process of continuously expanding the horizontal guiding tunnel,the influence law of the surrounding rock grade and construction method on the stability of the surrounding rock after the tunnel is completed is obtained,and the expansion of the V-class and worse surrounding rock conditions is determined.The flat guide hole will have a greater impact on the stability of the surrounding rock than the full-section excavation. |
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