Numerical Simulation of Tunnel Excavation in Soft Surrounding Rock of Shallow Buried Puma Water Rock

the soft rock tunnel of shallow buried Puma water rock is located at the underground interchange section of Xiangli high speed Hujiaoxia which is under construction. The lithology of the surrounding rock is mainly composed of limestone splint rock and slate rock intercalated limestone, which is difficult to construct and high in risk. It is the main control project of soft rock tunnel construction. On the basis of establishing reasonable engineering geological model, the section of typical soft rock tunnel of SC-1 type is selected as the research object, and the numerical simulation of tunnel construction schemes such as reserved core soil, single side tunnel and double side wall tunnel with FLAC3D software is carried out. Through the comparison and analysis of the stress and deformation of surrounding rock, it is proved that the double-side wall guide pit method is used in shallow underground excavation. Tunnel construction is safer. However, the construction cost of two-side guide wall construction method is higher, so the construction cost factor should be considered at the same time to meet the requirements of construction safety and surface settlement, which has higher numerical requirements for the selection of construction method. According to the requirements of numerical simulation, on-site monitoring, project cost budget and surface settlement, this paper considers that the construction scheme of double-side guide wall is suitable for this project, and can also control the surface settlement of shallow buried section by strengthening the supporting parameters of one-sided guide wall construction method. This study can be used for reference in the selection of similar tunnel construction methods.