Earth pressure on shield excavation face for pipe jacking considering arching effect

摘要

Pipe jacking is often used to install pipelines in congested urban areas or river crossings. The applied jacking force needs to be greater than the frictional resistance along the pipe and the face resistance. Lubricant slurries are usually employed to minimize the frictional resistance. Therefore, it is critical to estimate earth pressures acting on shield excavation face correctly. In this paper, the original Protodyakonov's arch model is modified to calculate the vertical pressure on deeply buried pipes. For shallow burial depth less than 5 m, the Terzaghi arching model is still applicable to estimate the vertical pressure. The soil prism in front of excavation face is divided into different zones to establish the force equilibrium. The calculated earth pressure is applied on top of soil wedges. The proposed analytical solution can analyze the stability of vertical and inclined excavation faces considering the influence of three-dimensional arching effect, as well as the contribution of soil cohesion. In the end, the effectiveness of the developed design framework is assessed by comparing calculations with experimental measurements of earth pressures on excavation face.