Underground » Coal Burst
Since 1995, under the support of US mining companies, the Bureau of Land Management, NIOSH and the School Institute for Trust Land Administration, significant effort has been dedicated to advance the understanding of violent failure mechanisms by identifying significant contributing factors. The objective of this project was to assist Australian operations by quantifying mining, geologic and geotechnical risk factors in US mines by re-examining burst prone case studies that address failure mechanism for three diverse coal fields.
This report reviews a study conducted by Maleki Technologies Inc for ACARP, to assist Australian operations to better understand coal burst mechanics and control based on US practical experience, investigations and inspections in three major US coal fields over the past five decades. The study examined both nonviolent and burst prone case studies to identify contributing risk factors and addressed failure mechanisms for major US coal fields in Utah, Colorado and Kentucky, which have diverse characteristics.
To investigate the mechanics of coal burst, a multi-pronged approach was used. First, field measurements in three mines from East Mountain, Utah are complemented with finite-difference stress analysis to address the importance of horizontal stress in coal pillar mechanics of violent failure. Second, computational procedures were reviewed for estimating seismicity resulting from slip along geological discontinuities, as these measurements point to seismicity being the trigger mechanism for violent failure of marginally stable structures. This joint-slip seismicity mechanism agrees with the more recent improved re-examination of MIS data from the Crandall Canyon Mine, Utah by the University of Utah. Third, a hybrid statistical-analytical methodology was applied for identifying significant factors affecting coal burst. It utilises data from 30 case studies including those from Utah, Colorado, Kentucky and other Eastern US mines providing predictive capability for the entire US coal fields. The statistical method reinforces comprehensive field measurements from Utah/Kentucky mines and points to strata rigidity, joint spacings and horizontal stress field as significant factors affecting damage resulting from coal bursts. This provides practical capabilities for identifying operations of higher risk using a rigidity-cavability variable. The Australian operations with intense and diverse horizontal stress regimes could be ideal in complementing the US data base, allowing a thorough re-examination of horizontal stress effects on the propensity of violent failure with a higher degree of confidence.
Overall, this study provides valuable insights into the mechanics and risk factors associated with coal bursts in major US coal fields. By utilising a multi-pronged approach that incorporates both field measurements and statistical-analytical calculations, the study offers practical capabilities for identifying operations of higher risk and improving coal burst control.