Study on Construction Stability and Initial Support Parameters Optimization of Large Section Tunnel
Based on Fengjie tunnel project of Zhengzhou-Chongqing High-speed Railway,the construction model of large section tunnel is established by using three-dimensional finite difference software,the stability of surrounding rock of large section tunnel construction by drilling and blasting method is studied,and the optimization parameters of initial support are proposed.The results show that the safety factor of the bare tunnel is 1.86 when the bench drilling and blasting method is used to excavate the level IV surrounding rock.Based on the load-structure model of structural mechanics,the safety factor of the original support scheme is 2.42,the maximum axial force of the anchor rod is 60.26 kN,the maximum subsidence of the vault is 2.85 mm,the maximum convergence of the side wall is 1.64 mm,and the maximum overall stress of the initial support is 7.04 MPa.After optimization,the safety factor is 2.13,the maximum axial force of bolt is 157.02 kN,the maximum subsidence of vault is 4.39 mm,the maximum convergence of side wall is 3.82 mm,and the maximum overall stress of initial support is 7.96 MPa.The on-site monitoring data is consistent with the numerical analysis results,verifying the rationality,economy,and reliability of the initial support optimization scheme.
large section tunnelsurrounding rock stabilitynumerical calculationstrength reduction methodinitial supportparameter optimizationfield monitoring
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