Coal bursts involve the sudden, violent ejection of coal or rock into the mine workings. They are a particular hazard because they typically occur without warning. During the past 2 years three US coal miners were kil...Coal bursts involve the sudden, violent ejection of coal or rock into the mine workings. They are a particular hazard because they typically occur without warning. During the past 2 years three US coal miners were killed in two coal bursts, following a 6-year period during which there were zero burst fatalities. This paper puts the US experience in the context of worldwide research into coal bursts. It focuses on two major longwall mining coalfields which have struggled with bursts for decades. The Utah experience displays many of the ＂classic＂ burst characteristics, including deep cover, strong roof and floor rock, and a direct association between bursts and mining activity. In Colorado, the longwalls of the North Fork Valley （NFV） also work at great depth, but their roof and floor strengths are moderate, and most bursts have occurred during entry development or in headgates, bleeders, or other outby locations. The NFV bursts also are more likely to be associated with geologic structures and large magnitude seismic events. The paper provides a detailed case history to illustrate the experience in each of these coalfields. The paper closes with a brief discussion of how US longwalls have managed the burst risk.展开更多
Coal bursts are typically associated with highly stressed coal.Most bursts occur during retreat mining(longwall mining or pillar recovery) in highly stressed locations like the tailgate corner of the longwall panel.Ot...Coal bursts are typically associated with highly stressed coal.Most bursts occur during retreat mining(longwall mining or pillar recovery) in highly stressed locations like the tailgate corner of the longwall panel.Others are associated with multiple seam interactions.However, a small but significant percentage of coal bursts have occurred during development or in outby locations unaffected by active mining.Most development bursts have been relatively small, but some have been highly destructive.No theory of coal bursts can be complete if it does not account for this type of event.This paper focusses on the development mining coal burst experience in the US, putting it into the context of the entire US coal burst database.The first documented development coal burst occurred almost exactly 100 years ago during slope drivage at the Sunnyside Mine in Utah.Sunnyside subsequently had a long history of bursts, mainly during retreat mining but also during development.Several Colorado mines have also experienced multiple development bursts.Many, but by no means all, of the development bursts in these western US coalfields have been associated with known faults.In the Central Appalachian coalfields, most development bursts have occurred in multiple seam situations.In some of these cases, however, there was no retreat mining in either seam.The paper closes with some lessons from this history, with implications for preventing such events in the future.展开更多
Thirty years ago, the analysis of longwall pillar stability(ALPS) inaugurated a new era in coal pillar design.ALPS was the first empirical pillar design technique to consider the abutment loads that arise from full ex...Thirty years ago, the analysis of longwall pillar stability(ALPS) inaugurated a new era in coal pillar design.ALPS was the first empirical pillar design technique to consider the abutment loads that arise from full extraction, and the first to be calibrated using an extensive database of longwall mining case histories.ALPS was followed by the analysis of retreat mining stability(ARMPS) and the analysis of multiple seam stability(AMSS). These methods incorporated other innovations, including the coal mine roof rating(CMRR), the Mark-Bieniawski pillar strength formula, and the pressure arch loading model. They also built upon ever larger case history databases and employed more sophisticated statistical methods.Today, these empirical methods are used in nearly every underground coal mine in the US. However,the piecemeal manner in which these methods have evolved resulted in some weaknesses. For example,in certain situations, it may not be obvious which program is the best to use. Other times the results from the different programs are not entirely consistent with each other. The programs have also not been updated for several years, and some changes were necessary to keep pace with new developments in mining practice. The analysis of coal pillar stability(ACPS) now integrates all three of the older software packages into a single pillar design framework. ACPS also incorporates the latest research findings in the field of pillar design, including an expanded multiple seam case history data base and a new method to evaluate room and pillar panels containing multiple rows of pillars left in place during pillar recovery.ACPS also includes updated guidance and warnings for users and features upgraded help files and graphics.展开更多
In order to reach a large,untapped reserve of high-quality coal,D8 Cloverlick Mine proposed to mine a corridor nearly 600 m deep beneath the Benham Spur of Black Mountain,Kentucky’s highest peak.D8 Cloverlick Mine wa...In order to reach a large,untapped reserve of high-quality coal,D8 Cloverlick Mine proposed to mine a corridor nearly 600 m deep beneath the Benham Spur of Black Mountain,Kentucky’s highest peak.D8 Cloverlick Mine was extracting the Owl seam,but the corridor’s route lay approximately 20 m above century-old mine workings in the C–(Darby)seam.Adding to the concern,three serious coal bursts had recently occurred in nearby Owl seam workings.Maps of the old workings seemed to indicate that the underlying C–seam had been fully extracted.However,two of the coal bursts had occurred above areas where the C–Seam was also shown as mined out.Mine Safety and Health Administration(MSHA)Technical Support therefore investigated the records of past mining to better understand the old mine maps.Underground conditions observed in current Owl seam workings were also compared with the maps of the old C–seam workings.The study concluded that the presence of hazardous underlying remnants could not be ruled out.To mitigate the burst risk,D8 Cloverlick Mine adopted a strategy of stress probe drilling.A self-propelled coal drill was used to auger 11.5-m-long,small diameter holes in advance of mining.As each hole was drilled,the cuttings were measured to detect the presence of highly stressed coal.Ultimately the crossing was successfully completed without incident.展开更多
The proliferation of unconventional gas well development in the Northern Appalachian coalfields has raised a number of mine safety concerns.Unconventional wells,which extract gas from deep shale formations,are charact...The proliferation of unconventional gas well development in the Northern Appalachian coalfields has raised a number of mine safety concerns.Unconventional wells,which extract gas from deep shale formations,are characterized by gas volumes and pressures that are significantly higher than those observed at many conventional wells.The gas is composed largely of methane as well as other hydrocarbons.Hundreds of planned and actively producing wells penetrate protective coal pillars or barriers within active mine boundaries,including chain pillars located between longwall panels.Gas released from a well damaged by mining-induced ground movements could pose a risk to miners by flowing into the mine atmosphere.The mining-induced ground movements that may cause well damage include conventional subsidence,non-conventional subsidence(e.g.bedding plane slip),pillar failure,and floor instability.This paper describes the known risk factors for each of the four failure mechanisms.It includes a framework that can guide the risk assessment process when mining takes place near gas or oil wells.展开更多
Longwall mining has existed in Utah for more than half a century.Much of this mining occurred at depths of cover that significantly exceed those encountered by most other US longwall operations.Deep cover causes high ...Longwall mining has existed in Utah for more than half a century.Much of this mining occurred at depths of cover that significantly exceed those encountered by most other US longwall operations.Deep cover causes high ground stress,which can combine with geology to create a coal burst hazard.Nearly every longwall mine operating within the Utah’s Book Cliffs coalfield has been affected by coal bursts.Pillar design has been a key component in the burst control strategies employed by mines in the Book Cliffs.Historically,most longwall mines employed double-use two-entry yield pillar gates.Double-use signifies that the gate system serves first as the headgate,and then later serves as the tailgate for the adjacent panel.After the 1996 burst fatality at the Aberdeen Mine,the inter-panel barrier design was introduced.In this layout,a wide barrier pillar protects each longwall panel from the previously mined panel,and each gate system is used just once.This paper documents the deep cover longwall mining conducted with each type of pillar design,together with the associated coal burst experience.Each of the six longwall mining complexes in the Book Cliffs having a coal burst history is described on a panel-by-panel basis.The analysis shows that where the mining depth exceeded 450 m,each design has been employed for about 38000 total m of longwall panel extraction.The double-use yield pillar design has been used primarily at depths less than 600 m,however,while the inter-panel barrier design has been used mainly at depths exceeding 600 m.Despite its greater depth of use,the inter-panel barrier gate design has been associated with about one-third as much face region burst activity as the double-use yield pillar design.展开更多
Multiple seam interactions are a major source of ground instability in several U.S.coalfields.Empirical methods are well suited for this problem,because while the mechanics multiple seam interactions are very complex ...Multiple seam interactions are a major source of ground instability in several U.S.coalfields.Empirical methods are well suited for this problem,because while the mechanics multiple seam interactions are very complex and poorly understood,many mining case histories are available for analysis.This study makes use of an updated database that includes 356 multiseam case histories,including 67 unsuccessful designs.The paper describes in detail the process used to design the study,collect the data,conduct the statistical analysis,and develop the quantitative model.The model can be used for mine planning in multiple seam situations,and has been made available as a module within the Analysis of Coal Pillar Stability(ACPS)computer program.展开更多
文摘Coal bursts involve the sudden, violent ejection of coal or rock into the mine workings. They are a particular hazard because they typically occur without warning. During the past 2 years three US coal miners were killed in two coal bursts, following a 6-year period during which there were zero burst fatalities. This paper puts the US experience in the context of worldwide research into coal bursts. It focuses on two major longwall mining coalfields which have struggled with bursts for decades. The Utah experience displays many of the ＂classic＂ burst characteristics, including deep cover, strong roof and floor rock, and a direct association between bursts and mining activity. In Colorado, the longwalls of the North Fork Valley （NFV） also work at great depth, but their roof and floor strengths are moderate, and most bursts have occurred during entry development or in headgates, bleeders, or other outby locations. The NFV bursts also are more likely to be associated with geologic structures and large magnitude seismic events. The paper provides a detailed case history to illustrate the experience in each of these coalfields. The paper closes with a brief discussion of how US longwalls have managed the burst risk.
文摘Coal bursts are typically associated with highly stressed coal.Most bursts occur during retreat mining(longwall mining or pillar recovery) in highly stressed locations like the tailgate corner of the longwall panel.Others are associated with multiple seam interactions.However, a small but significant percentage of coal bursts have occurred during development or in outby locations unaffected by active mining.Most development bursts have been relatively small, but some have been highly destructive.No theory of coal bursts can be complete if it does not account for this type of event.This paper focusses on the development mining coal burst experience in the US, putting it into the context of the entire US coal burst database.The first documented development coal burst occurred almost exactly 100 years ago during slope drivage at the Sunnyside Mine in Utah.Sunnyside subsequently had a long history of bursts, mainly during retreat mining but also during development.Several Colorado mines have also experienced multiple development bursts.Many, but by no means all, of the development bursts in these western US coalfields have been associated with known faults.In the Central Appalachian coalfields, most development bursts have occurred in multiple seam situations.In some of these cases, however, there was no retreat mining in either seam.The paper closes with some lessons from this history, with implications for preventing such events in the future.
文摘Thirty years ago, the analysis of longwall pillar stability(ALPS) inaugurated a new era in coal pillar design.ALPS was the first empirical pillar design technique to consider the abutment loads that arise from full extraction, and the first to be calibrated using an extensive database of longwall mining case histories.ALPS was followed by the analysis of retreat mining stability(ARMPS) and the analysis of multiple seam stability(AMSS). These methods incorporated other innovations, including the coal mine roof rating(CMRR), the Mark-Bieniawski pillar strength formula, and the pressure arch loading model. They also built upon ever larger case history databases and employed more sophisticated statistical methods.Today, these empirical methods are used in nearly every underground coal mine in the US. However,the piecemeal manner in which these methods have evolved resulted in some weaknesses. For example,in certain situations, it may not be obvious which program is the best to use. Other times the results from the different programs are not entirely consistent with each other. The programs have also not been updated for several years, and some changes were necessary to keep pace with new developments in mining practice. The analysis of coal pillar stability(ACPS) now integrates all three of the older software packages into a single pillar design framework. ACPS also incorporates the latest research findings in the field of pillar design, including an expanded multiple seam case history data base and a new method to evaluate room and pillar panels containing multiple rows of pillars left in place during pillar recovery.ACPS also includes updated guidance and warnings for users and features upgraded help files and graphics.
文摘In order to reach a large,untapped reserve of high-quality coal,D8 Cloverlick Mine proposed to mine a corridor nearly 600 m deep beneath the Benham Spur of Black Mountain,Kentucky’s highest peak.D8 Cloverlick Mine was extracting the Owl seam,but the corridor’s route lay approximately 20 m above century-old mine workings in the C–(Darby)seam.Adding to the concern,three serious coal bursts had recently occurred in nearby Owl seam workings.Maps of the old workings seemed to indicate that the underlying C–seam had been fully extracted.However,two of the coal bursts had occurred above areas where the C–Seam was also shown as mined out.Mine Safety and Health Administration(MSHA)Technical Support therefore investigated the records of past mining to better understand the old mine maps.Underground conditions observed in current Owl seam workings were also compared with the maps of the old C–seam workings.The study concluded that the presence of hazardous underlying remnants could not be ruled out.To mitigate the burst risk,D8 Cloverlick Mine adopted a strategy of stress probe drilling.A self-propelled coal drill was used to auger 11.5-m-long,small diameter holes in advance of mining.As each hole was drilled,the cuttings were measured to detect the presence of highly stressed coal.Ultimately the crossing was successfully completed without incident.
文摘The proliferation of unconventional gas well development in the Northern Appalachian coalfields has raised a number of mine safety concerns.Unconventional wells,which extract gas from deep shale formations,are characterized by gas volumes and pressures that are significantly higher than those observed at many conventional wells.The gas is composed largely of methane as well as other hydrocarbons.Hundreds of planned and actively producing wells penetrate protective coal pillars or barriers within active mine boundaries,including chain pillars located between longwall panels.Gas released from a well damaged by mining-induced ground movements could pose a risk to miners by flowing into the mine atmosphere.The mining-induced ground movements that may cause well damage include conventional subsidence,non-conventional subsidence(e.g.bedding plane slip),pillar failure,and floor instability.This paper describes the known risk factors for each of the four failure mechanisms.It includes a framework that can guide the risk assessment process when mining takes place near gas or oil wells.
文摘Longwall mining has existed in Utah for more than half a century.Much of this mining occurred at depths of cover that significantly exceed those encountered by most other US longwall operations.Deep cover causes high ground stress,which can combine with geology to create a coal burst hazard.Nearly every longwall mine operating within the Utah’s Book Cliffs coalfield has been affected by coal bursts.Pillar design has been a key component in the burst control strategies employed by mines in the Book Cliffs.Historically,most longwall mines employed double-use two-entry yield pillar gates.Double-use signifies that the gate system serves first as the headgate,and then later serves as the tailgate for the adjacent panel.After the 1996 burst fatality at the Aberdeen Mine,the inter-panel barrier design was introduced.In this layout,a wide barrier pillar protects each longwall panel from the previously mined panel,and each gate system is used just once.This paper documents the deep cover longwall mining conducted with each type of pillar design,together with the associated coal burst experience.Each of the six longwall mining complexes in the Book Cliffs having a coal burst history is described on a panel-by-panel basis.The analysis shows that where the mining depth exceeded 450 m,each design has been employed for about 38000 total m of longwall panel extraction.The double-use yield pillar design has been used primarily at depths less than 600 m,however,while the inter-panel barrier design has been used mainly at depths exceeding 600 m.Despite its greater depth of use,the inter-panel barrier gate design has been associated with about one-third as much face region burst activity as the double-use yield pillar design.
文摘Multiple seam interactions are a major source of ground instability in several U.S.coalfields.Empirical methods are well suited for this problem,because while the mechanics multiple seam interactions are very complex and poorly understood,many mining case histories are available for analysis.This study makes use of an updated database that includes 356 multiseam case histories,including 67 unsuccessful designs.The paper describes in detail the process used to design the study,collect the data,conduct the statistical analysis,and develop the quantitative model.The model can be used for mine planning in multiple seam situations,and has been made available as a module within the Analysis of Coal Pillar Stability(ACPS)computer program.
