Research on support design method of TBM tunnelling in deeply buried tunnels with large deformation potential: a case study of Bailong River Water Diversion Project

In the investigation and design stage of deeply buried water diversion tunnel, in order to carry out the support design of the tunnel section with the risk of large deformation, we put forward the method of identifying such tunnel sections by qualitative analysis, determining the classification of large deformation based on the 'empirical formula+unsupported condition, and determining the supporting parameters by taking into account the 'supporting effect+numerical analysis', and finally determined the support design method of reserved deformation.The basic concept and implementation process of large deformation support design for TBM tunneling peripheral rock were discussed, and the key technologies in the process of large deformation support design were studied in detail, including the prediction method of surrounding rock deformation, the tunnel deformation grading standard, and the idea of determining the amount of reserved deformation of surrounding rock.The above methods were applied to the design of large deformation support for the peripheral rock in the West Qinling Water Transfer Tunnel of the Bailongjiang Water Diversion Project, which reasonably ensured the large deformation interval and deformation classification for the TBM tunneling section of the tunnel, and identified the amount of reserved deformation in the TBM tunneling section, as well as parameters such as the thickness of the pipe sheet and the concrete grade.The research results form a scheme applicable to the support design of large deformation section of tunnel, which can provide a reference for similar projects.