99 / 2023-06-15 11:37:31

Response mechanism wave velocity and selection of seismic wave CT detection index of coal seam outburst danger: experiment and case study

seismic wave CT, coal seam stress field, wave velocity gradient, wave velocity anomaly coefficient

Coal and gas outburst seriously affect the safety of deep coal mine. Seismic wave CT detection is a new technology for detecting regional stress field. The research on the relationship between wave velocity derivative index and regional stress field is conducive to the further development of this technology. In our work, wave velocity, wave velocity anomaly coefficient and wave velocity gradient are applied to seismic wave CT detection to identify areas with large variation of stress disturbance in coal seams. The results show that the three indexes of wave velocity are positively correlated with stress, but the changes of wave velocity outliers and gradient indexes are more gently, and the correlation with stress is better. Due to the influence of geological structure such as valley, wave velocity V_p and wave velocity anomaly coefficient A_n of 11224 working face have large high-value abnormal areas. By comparing the distribution of gradient anomaly coefficient V_G of wave velocity change, it can be concluded that this high-value area is not a dangerous area. Hydraulic fracturing can reduce the stress in coal seam area, and the boundary of pressure relief zone can be determined by using wave velocity index. The comparative analysis of the three indexes of wave velocity proposed in this paper can reveal the stress distribution of coal seam more accurately. Combined with the actual geological structure characteristics of coal seam, it can realize the accurate identification of the stress disturbance region of coal seam, and achieve the purpose of predicting coal and gas outburst.