Abstract
Ground motions resulting from seismic waves are one of the main factors to trigger coal burst hazards in underground mines. Ground motion induced dynamic impacts may apply to the highly stressed coal/rock mass and initiate dynamic failure. Although ground motion analysis has been widely used in burst-prone hard rock mines for designing support systems, there are only few studies focusing on the understanding ground motion characteristics in coal mines and their relationship with the coal burst damage. Therefore, based on nine-months seismic monitoring in a case study coal mine, this paper conducted a thorough analysis on quantifying ground motions to roadways in both far-field and near-field zones and correlating strong ground motions to actual coal burst damage. The results showed that most far-field ground motions were insignificant, which were less likely to initiate coal burst damage. However, with the same energy levels and hypocentral distances, the seismic events in coal mines can produce higher far-field ground motions than those in hard rock mines. Compared with the far-field ground motions, the near-field ground motions had much higher intensities. The strong dynamic impacts induced by the near-field ground motions may trigger dynamic failure in coal or rock mass when it is already critically stressed. An index called the number of high ground motions (NHGM) was developed to link ground motions with burst risks in roadways. The roadway zone that had experienced a long history of intensive ground motions, indicated by a higher degree of NHGM, were more likely to expect coal bursts in the future.Article highlightsQuantify ground motions to roadways in both far-field and near-field zones in underground coal mines.Demonstrate the relationship between ground motion intensity and coal burst damage.Develop a method to forecast potential burst damage zones in roadways based on historical ground motions.
Highlights
Rockburst is a typical mining hazard, which describes an uncontrolled and violent ejection of rock fragments with excessive seismic energy after fracturing rock blocks (Cook 1965)
The ground motion intensity of a seismic event is commonly represented by peak particle velocity, which is the maximum velocity of particle movement when a seismic wave travels in coal and rock mass (Qiu et al 2021)
To comprehensively assess coal burst risks by using both far-field and near-field ground motions, an index called the number of high ground motions (NHGM) was proposed to investigate the relationship between the frequencies of intensive ground motions recorded in the past and actual burst damage observed in roadways
Summary
Rockburst is a typical mining hazard, which describes an uncontrolled and violent ejection of rock fragments with excessive seismic energy after fracturing rock blocks (Cook 1965). Ground motions and the induced dynamic impacts from these seismic events are one of the main factors to trigger coal and rockburst hazards (Cai et al 2020). Ground motion intensities of strong seismic events in hard rock mines have been linked with rockbursts in many different countries (McGarr 1984; Kaiser 1996; Cai and Kaiser 2018). A seismic database of Canadian hard rock mines suggests that severe damage is commonly caused by ground motions with ppv of larger than 0.6 m/s Such intensive ppv resulted from either a large scale event at far-field or a medium scale seismic event close to mine openings (Owen 2005). A new index named the Number of High Ground Motions (NHGM) was proposed to assess actual coal burst damage
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