Study on Pipe-Soil Contact State and Jacking Force of Rectangular Jacking

In order to reasonably predict the pipe friction resistance of rectangular pipe jacking and determine the jacking force more accurately, the pipe-soil contact state of rectangular pipe jacking is analyzed. When the grouting effect was good, the rectangular pipe section was floating in the mud; when the grouting effect was poor or the soil stability was poor, the contact state of pipe soil tended to be full contact. On this basis the four most likely contact states were full contact, contact on pipe roof together with both sides, contact on pipe roof together with one side, and contact on pipe roof. The theoretical calculation formulas of friction resistance between pipe and soil or slurry were derived respectively, the calculation results showed that the friction resistance could be ignored, the vertical pressure of rectangular jacking pipe could be well predicted by using the Terzaghi vertical earth pressure theory, and then the calculation models of friction resistance around pipe under different contact states were established. The numerical simulation of rectangular pipe jacking was carried out considering different pipe-soil contact states. Compared with the actual jacking force, the results showed that the errors between the numerical simulation and theoretical calculation and the measured value were only 13.2% and 8.5% respectively under the assumption that the pipe roof together with one side contacted with the soil.