Abstract: This study aims to establish a simulation method reflecting the initial macroscopic deformation of rock and propose a determining method for internal micro-cracks closure stress. Firstly, a deformation analysis model was established between rock matrix and micro-cracks, based on the stress and deformation characteristics of rock and its internal micro-cracks. Then deformation analysis methods were put forward for rock matrix and internal micro-cracks, respectively, according to the analysis of material deformation mechanics. Thus, an initially macroscopic constitutive model was deduced for rock, and its determining methods for the model parameters were also given. Secondly, a new method was proposed to obtain the closure stress of micro-cracks, due to the defects and deficiencies of those existing methods. Lastly, this study investigated the effect of confining pressure on the nonlinear concave degree of initially macro deformation of rock by using the established model. The theoretical result indicated that there was a negative correlation between them. Research results show that this established model can not only simulate the full deformation procedure of rock before failure, but also explain the deformation relationship between rock and their components. The new method can not only satisfy the theoretical significance of micro-cracks closure stress, but also avoid the interference of human factors. Moreover, this new method is easy to operate. Therefore, the above results verify the rationality and feasibility of the proposed model and method in this study.

Key words: rocks, micro-cracks, nonlinear deformation, constitutive model, confining pressure effect