A new model to predict soil pressure acting on deep burial jacked pipes

Soil pressure is a critical factor to pipe jacking projects both during and after the jacking. Current practices are based on modifications of one of Terzaghi arching model, e.g. Japan Microtunnelling Association, German standard ATV A 161, UK 'Pipe Jacking Association', ASCE 27, and Chinese standard GB 50332. In these practices, it is assumed that shearing bands arise from the outside of tunnel cross sections and extend to the ground surface. However, the shearing bands may desist below the ground surface (This scenario is called deep burial). If these practices are still applied, the calculations will result in underestimations. In this paper, a new calculation model, modified from the other Terzaghi arching model was proposed to specifically predict the soil pressure acting on the deep burial jacked pipes. Values of crucial parameters of the height of the shearing bands, friction angle, friction coefficient, soil pressure ratio, silo width and soil cohesion were analyzed based on published tunnel research results and trap-door experiments. The correctness of the new model was verified by in-situ measured soil pressure in Gongbei Tunnel project in Zhuhai city. In comparison to the in-situ measured soil pressure, the new model provided more logical estimations, while the current practices were found to underestimate the soil pressure.