In rectangular pipe-jacking, excessive friction force resulting from the pipe-soil interaction is the dominant factor hindering its further application in long-distance, larger-section, and deep-buried scenarios in urban underground construction. These complex scenes are the frontiers and key issues that need to be developed in this method. To this effect, this paper aims to investigate the pipe-soil interaction and improve the prediction accuracy of the friction force in rectangular pipe-jacking. The widely used friction force solutions were examined based on the actual monitoring data via two field cases in Japan. The reasons for the current overestimation of the friction resistance in rectangular pipe jacking were discussed. To avoid the prediction deviation in the empirical and theoretical formulas, a new pipe-soil contact model for rectangular pipe-jacking was proposed for friction force prediction under the lubricant applied condition. Further, a numerical simulation was conducted using the finite element method to verify the proposed model. Combining the numerical results and field data, the developed model was preliminarily proved and it could provide the prediction accuracy of friction force within 5.5% in the greater Tokyo area. The results suggest that the improved friction force prediction could provide a reference for future designs of long-distance rectangular pipe-jacking.
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