Abstract:

To analyze the spatial distribution characteristics of the stress and displacement of the back wall and soil of circular pipe jacking working shaft in Grade V surrounding rock, the stability monitoring of the circular pipe jacking working shaft of Zhijiang End reservoir drainage project is monitored, and a threedimensional numerical model is established to study the influence of size parameters of shaft structure and jacking force on the horizontal displacement of back wall soil. The results of actual measurement and simulation show the following: (1) The maximum value of horizontal displacement and vertical stress distribution of soil at the back wall appear in the range of jacking force. There is a tensile stress concentration area at the back wall within 2.5 m from the outer side of the left and right sides of the backrest steel plate, and the tensile stress concentrates on the height of the backrest steel plate along the shaft depth. (2) The shaft wall thickness has the greatest influence on the horizontal soil displacement, followed by the middle backrest thickness, and the bottom plate thickness is the smallest. When optimizing the structure size to improve soil stability, the rear backrest thickness should be prioritized. (3) For pipe jacking in a moderatelyweathered muddy siltstone layer, the change in the rock-socketed depth of the working shaft slightly affects the horizontal soil displacement on the back wall, showing that the rock-socketed treatment is unnecessary for the shaft wall. (4) The horizontal displacement of back wall soil is linearly related to the jacking force of a cylinder. 

Key words: pipe jacking, circular working shaft, back wall, stress, displacement, numerical simulation, Grade V surrounding rock