Research on the Characteristics and Treatment Measures of Large Deformation of Shallow Buried Layered Soft Rock Tunnels
The Xinhuashan Tunnel of Zhangjiajie-Jishou-Huaihua High-speed Railway encountered serious asymmetric and three-dimensional large deformation when passing through the carbonaceous shale layer.To solve the problem of large deformation in shallow buried layered soft rock tunnels during the excavation process,a three-dimensional layered surrounding rock tunnel numerical model was established,and the large deformation characteristics and mechanisms of shallow buried layered soft rock tunnels were analyzed.The results show that the mechanical properties of soft rocks are the important factors causing significant deformation in the Xinhuashan Tunnel.The joint in the shallow buried section of the tunnel mouth has a significant contribution to large deformation,and the interlayer deformation of the carbonaceous shale layer in the Xinhuashan Tunnel contributes nearly 50%to the total deformation value.The interlayer deformation in the region where the joint is in contact with the tunnel contour is the most significant.Under gentle slope conditions,the deformation is concentrated at the arch top,while under steep slope conditions,the risk of tunnel wall failure increases rapidly.According to the field deformation characteristics and numerical simulation results,the reinforcement measures of surface casing grouting are proposed and significant effects are achieved.The research results can provide reference for the prevention and treatment of large deformation in similar shallow buried layered soft rock tunnels.
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