Abstract: The accurate calculation of extra-large diameter slurry shield in soft soil should be improved. As a result, the main components of thrust force and cutterhead torque of extra-large diameter slurry shield used in Su′ai Tunnel are analyzed. A theoretical calculation model for thrust force and cutterhead torque is established based on the soil stratification of tunnel excavation face. A calculation program is developed based on the deduced equations by using MATLAB application and the relative parameters of Su′ai Tunnel. The comparison results between the field data and calculation data show that: (1) The error between field measured data and predicted data of thrust force and torque is less than 10%, which illustrates that the calculation model mentioned-above has a higher accuracy than Krause model and Ugur Ates regression. (2) The proportion of slurry resistance is the highest in total thrust, followed by that of friction resistance between shield shell and soil layer, and that of cutter resistance is little. (3) The cutting torque accounts for the highest proportion of cutterhead torque, followed by that of friction torque between cutterhead and the slurry. The torque is more sensitive to the strata rather than the thrust force.

Key words: soft soil, slurry shield, thrust force, torque, calculation model