A peridynamic strainburst model for evaluating the strainburst and its dependency on the loading and unloading

The strainburst observed in laboratory model test, where a cubic rock sample with an opening is compressed until a strainburst is induced, is generally triggered by the loading stress. In contrast, in real-world engineering contexts, such strainbursts are triggered by tunnel excavation, which corresponds to the effect of unloading stress. This paper aims to study the similar and different strainburst mechanisms triggered by loading and unloading effects. Firstly, the PD method incorporating the in-situ stress into the its constitutive relationship is proposed for computational efficiency. Secondly, the PD strainburst model, which can distinguish the crack propagation from strainburst, is proposed by introducing the energy-based strain strainburst criterion. Thirdly, the proposed model is verified by simulation of tunnel excavation process and mine-by experimental tunnels. Finally, the comprehensive analysis of influence of loading and unloading on the strainburst mechanisms are conducted. The results demonstrate that the variation of energy over time for loading and unloading cases are significantly different and the trend in the intensity of strainbursts around the chamber can be referenced from the results of the laboratory model test.