Abstract: The loading mechanism under the action of jacking counterforce of rectangular working shaft by soil mixing wall (SMW) methods is investigated. Assuming the horizontal earth counterforce distributed equably, vertical earth counterforce at the back of loaded wall is considered as quasi-normal distribution, a formula for calculating maximal earth counterforce at the back of loaded wall is obtained. Assuming the soil at the front of loaded wall is at active state, formulas for the maximal earth counterforce and permitted jacking force of working shaft are obtained. The analytical calculation results of an example show that the maximal earth counterforce at the back of loaded wall by trapezoidal distributing method is some greater than one with the method presented in text. The permitted jacking force calculated by estimating water and earth pressure together in cohesive soil is highly close to the maximal jacking force measured in field.

Key words: pipe jacking, soil mixing wall (SMW) methods, working shaft, earth counterforce, jacking force