Objective Current researches on slurry pressure calculation theories are fragmented, mainly focusing on the application of a single specific calculation theory or analyzing only one type of geological condition, without systematic comparison and summary. Accordingly, it is necessary to conduct a systematic engineering comparative analysis of calculation theories for the slurry pressure at shield tunnel excavation faces.

Method A calculation theory for the above-mentioned slurry pressure is proposed. To investigate the adaptability of different theories under various stratum conditions, field data are collected from multiple shield tunnels that traverse differing strata, and on-site monitoring of slurry pressure values during tunnelling is carried out. Given the complexity and low efficiency of manually calculating full-line excavation face slurry pressure for shield tunnels, a MATLAB program is developed to rapidly compute the theoretical values derived from the proposed theory. Measured slurry pressure values are then comparatively analyzed against the theoretical calculated values. Meanwhile, numerical models for diverse working conditions are established using the finite difference software FLAC3D, and the adaptability of the proposed calculation theory is verified through simulation analysis. Finally, division intervals of stratum permeability for water-soil separated pressure calculation and water-soil combined pressure calculation are obtained in combination with the permeability coefficients of the strata shield tunnels traverse.

Result & Conclusion  For the sandy and gravel strata under shallow-buried conditions, the Rankine active earth pressure calculation theory is recommended. For the clay strata under shallow-buried conditions, a three-dimensional wedge mode calculation theory based on the full-soil column theory is suggested. For the sandy strata under deep-buried conditions, Terzaghi's loosening earth pressure calculation theory is preferred, and for the clay strata in same conditions, a three-dimensional wedge mode calculation theory built upon the above Terzaghi's calculation is advised. Water-soil separated pressure calculation is recommended for sandy strata with a permeability coefficient greater than 1×10⁻³ cm/s, whereas water-soil combined pressure calculation is preferred for clay strata with a permeability coefficient lower than 6×10⁻⁶ cm/s.