Multi-field coupling dynamic evaluation method of rockburst hazard considering dynamic and static load

Static basic quantity and dynamic variation quantity exist in the process of rockburst in deep mining. Dynamic load disturbance and the increasing of in-situ stress field are the source of rockburst. Therefore,the dynamic and static load must be considered comprehensively in the fast and high-precision evaluation of rockburst hazard. Hopkinson pressure bar experiments and numerical simulations were carried out to analyze the influences of dynamic load on the damage and stress field of the coal rock. In view of the fact that the change of stress could directly cause the change of vibration wave velocity and the amplitude before and after the change of wave velocity were affected by the stress field,the coupling relationship between vibration field and stress field was mastered and the multi-field coupling dynamic evaluation method of rockburst hazard was established. In the process of catastrophe,the in-situ stress field represents the static foundation quantity,and the mining stress field and the vibration field represent the dynamic change quantity. The wave velocity anomaly index,wave velocity gradient index,stress anomaly index and stress gradient index are used as evaluation indexes to realize dynamic evaluation of rockburst hazard. The results show that the energy is transmitted in the form of vibration wave under dynamic load,resulting in the redistribution of stress field. The stress presents the characteristics of zonal transmission,and causes the damage of coal and rock when the energy reaches a certain threshold. However,no matter the dynamic load directly acts on the rock or the coal,the rock is the energy transfer path,the coal seam is the main body of energy dissipation and release,and the failure mainly occurs in the coal. The multi-field coupling dynamic evaluation method of rockburst hazard was applied on a certain working face. The rockburst hazard was reduced from strong to medium in the process of gradually exposing faults. The field monitoring data showed that the evaluation results were consistent with the actual situation.