| In the construction of expressways in mountainous areas,tunnel engineering occupies a very important position.Affected by topography,unfavorable geological conditions such as high side elevation,large bias pressure and shallow burial frequently appear at the tunnel entrance section.How to ensure the stability of the tunnel entrance section side elevation slope and choose a safe and reasonable tunnel entrance construction plan is tunnel engineering One of the most difficult points.The thesis is based on the construction of the No.3003 tunnel project in the F3 section of the Georgia E60 expressway under construction,using a combination of numerical simulation and on-site monitoring and measurement,to support the plan of the side slope of the tunnel entrance and the entrance plan of the tunnel entrance.Research has been conducted,and the main research content and results are as follows:(1)Considering the geological changes of the tunnel entrance section,based on the supplementary geological survey data of the tunnel entrance section and using Midas GTS NX software,a numerical analysis model of the tunnel entrance section was established to simulate the stability of the tunnel entrance slope under the original support scheme The analysis results show that the original support scheme is difficult to meet the stability requirements of the side slope construction,and it is necessary to carry out the supporting design of the side slope of the cave entrance based on the supplementary geological data.(2)Based on the analysis of the supplementary survey geological data,a modified support plan for the side slope of the tunnel entrance section is proposed.The numerical simulation method was used to establish a numerical analysis model of the tunnel entrance section under the changed support scheme,and comprehensively analyze the displacement,stress and stability of the tunnel entrance section side slope,verifying that the tunnel entrance section side slope support after the change was changed The security of the program.(3)Using the method of numerical simulation,the numerical analysis models of the tunnel entrance section of three auxiliary construction measures were established respectively,and the construction stability of the tunnel entrance section under different construction schemes such as the full-section method and the bench method were numerically simulated and analyzed.Based on the comprehensive analysis of the surface displacement of the tunnel entrance section caused by the construction,the deformation and stress of the surrounding rock of the tunnel,and the mechanical characteristics of the tunnel supporting structure,it is suggested that the tunnel entrance section adopts the step method construction plan,and the tunnel entrance section adopts the pipe shed.Grouting and reinforcing the core soil with glass fiber components determine auxiliary construction measures for construction stability.(4)Numerical simulation analysis of the proposed step method construction scheme is carried out,and the construction stability characteristics of the tunnel entrance section under different step lengths are studied.Based on the results of numerical simulations,comprehensive comparative analysis is made from multiple aspects such as the surface displacement of the entrance section,the deformation and stress of the surrounding rock of the tunnel,and the stress characteristics of the supporting structure.It is recommended that the step length of the entrance section is10 m.(5)Carrying out the on-site construction monitoring of the tunnel entrance section,based on the on-site monitoring and measurement data,studied the surface settlement of the slope and the change law of the surrounding rock deformation in the tunnel.The on-site monitoring results and the numerical simulation results were compared and analyzed,which verified the rationality and feasibility of the slope support and tunnel entry construction plan determined in the thesis. |
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