Research On Supporting Parameters Of Leading Small Conduit In Shallow Buried And Undercut Metro Station Under Ground Surface Grouting

Under the background of economic globalization,the process of urbanization in our country is accelerating.Urban rail transit has gradually become the most important mode of public transportation in modern cities due to the advantages of fast speed,large volume,low noise,punctuality,and high safety.Urban rail transit is mostly tunnel engineering,and has the characteristics of large cross-section,shallow depth,long mileage,and complex surrounding environment,so the construction is more difficult.In order to ensure construction safety,economy,and timeliness,the surrounding rock of the tunnel with poor geological conditions and weak bearing capacity needs to be reinforced with advanced support,and the advanced small pipe has the characteristics of strong adaptability,simple technology,and low cost.Become the most widely used advanced support method.Based on the Yuegang Avenue Station on the northern extension of Chongqing Rail Transit Line 5,this thesis uses a combination of theoretical analysis,numerical simulation,and monitoring and measurement to study the support of shallow-buried and under-cut subway stations under the condition of surface grouting Application effect and design parameter optimization.The main research results are as follows:(1)According to the survey and design data of the supporting project and the actual situation of the site,through theoretical analysis,it is determined that the shallow-buried and underground-excavated subway station under surface grouting should be supplemented and reinforced by the use of advanced small conduit support.(2)Using MIDAS/GTS NX software,a numerical model of shallow-buried super-large cross-section tunnels under the condition of surface grouting is established,and the surrounding rock deformation,surrounding rock stress,and initial stress are compared and analyzed under the conditions of not using the leading small pipe and using the leading small pipe Support structure stress,the results show that the use of advanced small pipe support in the case of surface grouting has obvious effects on improving the stability of surrounding rock.(3)By simulating the support effect of small pipes under different extrapolation angles,circumferential distances,layout ranges and other parameters,the support parameters of the leading small pipes under surface grouting are analyzed on the surrounding rock deformation,surrounding rock stress,and initial support structure stress.The influence law of the axial force of the small catheter,and finally summarized the best design parameters of the advanced small catheter support under the condition of surface grouting relying on the project.(4)Obtain the actual data of the vault settlement,surface settlement,and clearance convergence of the subway station under surface grouting and reinforced with advanced small pipes under the surface grouting method,and compare the actual data with the calculated results to verify the values.Reliability of simulation results.