ABSTRACT
Since the behaviour of rock mass surrounding the openings in response to the excavation is deeply depending on the state of in-situ stresses, the understanding of relationship between in-situ stresses and the mechanical response and possible failure of rock mass is essential in order to provide the means to make a proper design. This paper gives the new analytical solutions to describe the two-dimensional elasto-plastic behaviour of a rock opening under non-hydrostatic loading condition. The rock mass is assumed as a linear dilatant material and exhibits post-failure behaviour after the peak stress. Based on the analysis of the loading history of in-situ stress state, the plastic behaviour and modes of plastic zones around the opening in soft rock masses are explicated. Explicit formulations of the plastic stress field and of the plastic radii, which are applicable in every case for two-dimensional model, are obtained using a coupled Plasticity-Complex Function Method. The adequateness of the proposed method is verified by some case studies.
