Macro-micro mechanical model for progressive and creep failure of brittle rock

The progressive and creep failure of brittle rock in compression plays an important role in the investigation of rock mechanics. It has great significance for judging the stability of surrounding rock in deep underground. Furthermore, growth of microcracks of brittle rock has great influence on creep properties. Based on the relation between stress and crack growth, and on the evolution law of crack growth, and considering the link of damage in micromechanical and macroscopic scales, a new macro-micro model is proposed. The theoretical expressions for stress-strain relationship and creep are derived. The effects of confining pressure on the relationship between stress and strain are analyzed. The effects of initial mcirocrack size and friction coefficient on stress-strain relationship and rock strength are also investigated. The crack initiation stress and the peak stress under different confining pressures are obtained, which provides a reference for applied stress under creep tests. The creep strain and strain rate under constant confining pressure and step axial loading are analyzed. Rationality of theoretical results is verified by these experimental results. It may provide the theoretical reference for understanding the effects of microcrack growth on the mechanical properties of brittle rock in compression.