Abstract: In this paper, the statistical meso-damage theory was introduced to study the deformation and failure mechanical properties of brittle rock in the post-peak region. The limitations and the deficiencies of the damage variables defined by the ratio of the damaged miro-element number to the total number were discussed. The meso-damage evolution mechanism of brittle rock was analysed based on the post-peak deformation and failure characteristics of the heterogeneous rock. The modified damage model was established considering the non-uniformity of the rock material caused by the damaged micro-element. Meanwhile, the function hypothesis of the modified model coefficient was proposed. Then, based on this, the modified statistical damage constitutive model of rock was established, and the methods of determining the model parameters were given. Finally, the theoretical curves of this model were compared with the experimental curves, and the variation law of the model parameters was discussed. The research shows that this model can reflect the different stress dropping rate of brittle rock in the post-peak region. The theoretical curve and variation law of the model parameters are in good agreement with the experimental results, which indicates that the proposed model and methods have certain rationality and feasibility.

Key words: brittle rock, stress dropping rate, non-uniformity, damage, constitutive model