Abstract: The pressure balance method is adopted in calculating the stability against the inrush of excavation in the current criterion. The effects of soil strength and excavation size are not considered in this method. Therefore, the method gives a conservative evaluation of the situation approaching the critical artesian pressure. Aiming at these problems, firstly, the safety factor is defined according to the principle of shear strength reduction in this paper. The existing method considering soil shear strength along slip surfaces is improved by adopting effective stress analysis and considering the passive zone of excavation. Then, a new calculation method for inrush resistance is proposed based on the elastic plate theory. Subsequently, the results of the finite-element method with reduced shear strength are compared with those of above calculation methods under the plane strain condition. And the effects of the excavation length-width ratio for the improved and proposed methods are further analyzed. Finally, the analysis of an engineering practice is carried out. The analysis shows that compared with the existing methods, the improved and proposed methods in this paper can better reveal the trends of excavation stability against inrush with the change of the artesian pressure and improve the economy on the premise of ensuring the safety of engineering practice.

Key words: stability against inrush, artesian water, shear strength reduction, effective stress, pressure balance method