Abstract: Based on the theory of fast Lagrangian analysis of continua, the theoretical basis of the stress release method is discussed. Through the analysis of a case in which the excavating and unloading process of a circular tunnel is simulated by using the stress release method and the three-dimensional simulating method respectively; the problems including the differences of stress paths, the accuracy of the calculating results and the applicability of the stress release method are discussed. Firstly, the results indicate that the stress paths are different in these two methods. So, the stress release method can simulate the excavation in tunnel engineering only in some limitation. Secondly, as to the material with the nonlinear mechanical property, the different stress paths induce the different results. But, the results from the two methods are equal approximately if the required conditions are satisfied and the error magnitude will decrease with the increase or decrease of the confining-pressure coefficient from 1.0. Finally, GRC in the convergence- confinement method can be obtained simply through the stress release method; and it indicates the importance of this method in the corresponding application.

Key words: tunnel, FLAC3D, stress release method, stress path, true three-dimensional simulating method, confining pressure coefficient, convergence-confinement method