: The National Institute for Occupational Safety and Health (NIOSH) has continued the research role of the former US Bureau of Mines (USBM) to engineer techniques that will reduce the hazards in the mining work place associated with coal bumps. Recent research focused on a longwall coal mine in Utah with overburden greater than 750 m (2,500 ft) containing several massive sandstone units. The primary field instrumentation at the site was three-dimensional, full waveform, autonomous microseismic arrays placed underground and on the surface in order to surround the active multi-panel longwall district. The purpose of these arrays was to help investigate the strata mechanics associated with the redistribution of stress and the associated gob formation of the longwall. Specifically, the seismic arrays were used to determine the timing and location of the failure in the strata surrounding the active mining. Overall 13,000 seismic events were detected and located with on-site processing during the five months the panel was being mined, including a magnitude (ML) 4.2 event. Of these, a smaller subset of 5,000 well-located events was selected during post-processing to form a consistent data set for analysis in this paper. From this data set, it was observed that the seismic events generally occurred in advance of the longwall face, both above and below the panel, consistent with failure of the strata in the forward stress abutment zone. Also, the occurrence of the ML 4.2 seismic event within 150-180 m (500-600 ft) of a deep cover longwall face with no associated bump caused a reevaluation of the nature of the connection between seismic activity and coal bumps.
Coal mine bumps, sometimes referred to as outbursts, bursts, or bounces, have been recognized as a serious problem in mining for more than 75 years. For the purposes of this paper, a bump is defined as a sudden release of strain energy that results in the expulsion of coal from a rib, pillar, or floor in a catastrophic manner. Beginning as early as the 1930''s, the US Bureau of Mines (USBM) conducted research investigating the causes and potential mechanism of bumps in order to avoid injuries in coal mines (Rice 1936). Research conducted by the National Institute for Occupational Safety and Health (NIOSH) continues to focus on the reduction of bumps and bump hazards.