Analysis of the Surrounding Rock Deformation and Structural Stress on the Bias Tunnel by Block Excavation Sequence
Based on the engineering background of Zhencai Tunnel of Rongfu Expressway,the block excavation method of reserved core soil lower step is proposed.The FLAC3D finite difference program is used for three-dimensional simulation analysis.The surrounding rock deformation and supporting structure stress of the reserved core soil lower step block method,the traditional reserved core soil method and the middle partition wall method are compared and analyzed,and the reasonable excavation sequence is discussed.The results show that the surrounding rock deformation and structural stress of the tunnel are asymmetric under the condition of shallow buried bias.The maximum surface settlement occurs on the deep buried side of the tunnel center,and the vertical displacement of the arch shoulder and the arch waist is larger on the deep buried side than the shallow buried side.The surface settlement,vault settlement and the maximum axial force of the bolt in the shallow buried side by the reserved core soil lower bench block method are smaller than those by the traditional reserved core soil method,which is beneficial to control the stability of surrounding rock and support.The middle partition wall method is better to control the surface settlement and the vertical displacement of the surrounding rock by excavating the deep buried side first,while the shallow buried side is better to control the horizontal displacement and the lining structure is less stressed.
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