Parameter Selection for Construction of HSR Single-track Tunnel Class Ⅳ Surrounding Rock by Benching Tunnelling Method
Based on Qinling Mabaishan Single-track Tunnel of Xi'an-Shiyan HSR,this paper uses a three-dimensional finite element calculation model to study the change law of surrounding rock deformation and primary support structure stability under different bench heights and lengths during construction by benching tunnelling method.The results show that:a)the bench height has a great impact on tunnel face deformation,plastic zone distribution,arch crown settlement and primary support convergence;b)the longitudinal deformation of the tunnel face with different bench lengths is small.With the increase of bench length,the maximum arch crown settlement and primary support convergence deformation gradually increase.When the bench length reaches 20 m,both tend to be stable;c)for Class Ⅳ surrounding rock sections,the bench height of single-track tunnel should be 6.5～8.0 m.Considering the arrangement of tunnel construction machinery and equipment,it is appropriate to take the bench length as 20-40 m.During tunnel construction,the monitoring results of arch crown settlement and primary support convergence meet the construction safety requirements,which verifies the feasibility of the study results and can provide reference for the construction of related projects by benching tunnelling method.
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