Damage constitutive model of rock subjected to coupled static loadings and cyclic impacts

Establishing a suitable damage constitutive model of rock is of great significance to study the dynamic mechanical characteristics of rock subjected to coupled static loadings and cyclic impacts. Firstly, the parameter of cyclic impact times was introduced to the damage constitutive relation of rock with the relationship between the elastic modulus of rock and the accumulative damage variable which based on the evolution model of damage accumulation of rock subjected to coupled static loadings and cyclic impacts. Secondly, combining the statistic damage model and visco-elastic model, a rock dynamic damage constitutive model was established under the axial pressure and the confining pressure and cyclic impacts based on the Drucker-Prager failure criterion with the assumption that the rock micro unit strength complied with the Weibull distribution. Then, the experimental data with coupled static and dynamic loadings on rock was used to verify the correctness and feasibility of the damage constitutive model. Finally, the influence law of parameters to the stress-strain curve was studied in the process of cycle impact in the model. The results show that there is a good coherence between the established damage constitutive model of rock and the experimental data, which can also reflect a constitutive relation of rock subjected to coupled static loadings and cyclic impacts. The parameters of elastic modulus and viscosity coefficient of rock have a great influence on the stress-strain curve in the process of cycle impact, but the parameters of friction angle and Poisson's ratio of rock have little influence on the impact of fatigue stress-strain curve of rock which is under 3D static loadings. In the process of cycle impact, the non-uniformity of rock gradually increases. The results are beneficial to improve the dynamic fatigue mechanics theory system of rock subjected to coupled static loadings and cyclic impacts.