Research and application of balance mechanism of excavation surface of slurry shield tunnels considering cutterhead thrust

In the existing balance mechanism of the excavation surface of slurry shield tunnels, the support of the excavation surface is mostly considered to be provided by mud pressure, and the role of cutterhead thrust in the support is rarely mentioned. In response to the specific problem of excavation surface support in the Chuanqin slurry shield tunnel project, based on the analysis of the main control parameters of excavation surface support, the balance mechanism of the excavation surface of the slurry shield tunnel considering the cutterhead thrust is revealed, and a specific expression for the cutterhead thrust is proposed. Using the revealed equilibrium mechanism and the proposed method for estimating the external frictional resistance of the shield shell, the calculation of excavation support force and the stability analysis are conducted for the three key crossing sections of the project. The research shows that in the excavation of the three key crossing sections, the cutterhead thrust accounts for 21%, 24% and 11% of the excavation face support force, respectively. Considering both the mud pressure and the cutterhead thrust, the proportion of the combined axial water and soil forces in the presence range in front of the excavation face increases from 0, 0 and 78% to 78%, 32% and 88%, respectively, compared to only considering the mud pressure. It is indicated that the cutterhead thrust plays an important role in the excavation face support.