Research on Failure Mechanism and Prevention Measures of Gently Dipping Layered Rock Mass in Xi'an-Yan'an HSR Tunnel
In view of the primary support deformation and failure problems of lower Jurassic shale intercalated with sandstone gently dipping layered rock mass in New Yan'an Tunnel of Xi'an-Yan'an HSR,this paper uses the static structure and characteristic value buckling module of workbench to model the support structure,analyzes the failure mechanism of the primary support structure,and optimizes the support measures.The study shows that:(1)The deformation and failure of surrounding rock and support structure of tunnel in gently dipping layered rock mass are mainly affected by geological factors such as lithology of gently dipping layered rock mass and gently dipping bedding structure;(2)The failure mode of the support structure is in-plane buckling of the support structure,resulting in instability when the pressure of surrounding rock reaches the bearing limit of primary support structure material and crushing damage when the pressure continues to increase;(3)The deformation of surrounding rock of tunnel in gently dipping layered rock mass is complex,and the deformation time of surrounding rock after tunnel excavation is long,so rigid support should be adopted.Compared with the originally designed grid support,the use of steel support is more reasonable in terms of deformation control and bearing capacity of gently dipping layered rock mass.
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