Abstract: Accurate prediction of the jacking force in rectangular pipe jacking projects is difficult under varying slurry lubrication conditions. To address this challenge, the jacking force variation pattern of a pipe jacking project in Shanghai, China, is measured. The jacking process is categorized into three conditions: no slurry, gradual slurry, and full slurry lubrication. Second, the trapezoidal wedge model is used to calculate the head-on resistance of the rectangular pipe jacking. Based on the modified Tershaji loose-earth pressure and slurry lubrication conditions, the contact state and interface friction factor between the pipe and soil under the three slurry lubrication conditions are analyzed. A new method for predicting the rectangular jacking force is developed by considering the friction resistances of the pipe-soil and pipe-slurry interfaces, thus proposing a calculation method for the lateral friction resistance under different slurry lubrication conditions. Finally, the results are compared with the field-measured data and calculations based on the existing rectangular pipe jacking specifications. The results demonstrate the following: (1) The proposed model exhibits higher prediction accuracy, with an error between the proposed model and the measured jacking force within ±15%, thus validating its rationality. (2) Under the initial condition with no slurry lubrication, the lateral friction resistance should be calculated using a full-contact model between the pipe and soil and the corresponding interface friction factor without lubrication. When slurry lubrication is fully used in later stages, calculating the lateral friction resistance using the interface friction factor under lubricated pipe-soil contact conditions yields more accurate results. Under gradual slurry lubrication conditions, the contact states between the pipe and soil quickly change from full contact to one-sided contact.

Key words: rectangular pipe jacking, slurry, lubricant condition, jacking force, lateral friction resistance, pipe-soil contact