Rockburst characteristics in syncline regions and microseismic precursors based on energy density clouds

Cases of rockbursts were investigated to analyze the influence of syncline structures on rockbursts. In a syncline structure in Xing'an Coal Mine, the relationship between the activity of mining-induced tremors and a violent rockburst was studied from temporal and spatial distribution graphs of tremors and pictures of energy density clouds. The results indicated that the temporal and spatial distributions of tremors before the rockburst intuitively illustrate areas in which tremors were concentrated; however, the tremors showed more complex spatial distribution characteristics, and it was difficult to identify the evolutionary trends in tremors over time. Energy density clouds exhibited obvious nucleation characteristics, and presented an obvious extension around the nucleus until a rockburst or strong tremor happened around the edges thereof. High-stress regions formed due to the syncline structure can be identified by applying seismic velocity tomography. According to the distribution of wave velocity, large-diameter hole drilling and deep-hole blasting were implemented in targeted areas. The activity of tremors induced by the follow-up mining confirmed the effectiveness of these stress relief measures.