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Unanticipated multiple seam stresses from pillar systems behaving as pseudo gob–case histories

International Journal of Mining Science and Technology 2017年第1期27卷 131-137页

作者： gauna michael Mark Christopher Pittsburgh Safety and Health Technology Center Mine Safety and Health Administration(MSHA)PittsburghPA 15236USA

Underground coal mining in the U.S. is conducted in numerous regions where previous workings exist above and/or below an actively mined seam. Miners know that overlying or underlying fully extracted coal areas, also known as gob regions, can result in abutment stresses that affect the active mining. If there was no full extraction, and the past mining consists entirely of intact pillars, the stresses on the active seam are usually minimal. However, experience has shown that in some situations there has been sufficient yielding in overlying or underlying pillar systems to cause stress transfer to the adjoining larger pillars or barriers, which in turn, transfer significant stresses onto the workings of the active seam. In other words, the overlying or underlying pillar system behaves as a ‘‘pseudo gob." The presence of a pseudo gob is often unexpected, and the consequences can be severe. This paper presents several case histories, summarized briefly below, that illustrate pseudo gob phenomenon:(1) pillar rib degradation at a West Virginia mine at 335 m depth that contributed to a rib roll fatality,(2) pillar rib deterioration at a Western Kentucky mine at 175 m depth that required pillar size adjustment and installation of supplemental bolting,(3) roof deterioration at an eastern Kentucky mine at 400 m depth that stopped mine advance and required redirecting the section development,(4) coal burst on development at an eastern Kentucky mine at 520 m depth that had no nearby pillar recovery, and(5) coal burst on development at a West Virginia mine at the relatively shallow depth of 335 m that also had no nearby pillar recovery. The paper provides guidance so that when an operation encounters a potential pseudo gob stress interaction the hazard can be mitigated based on an understanding of the mechanism encountered.

关键词： Underground mining Coal Multiple seam Gob Ground control

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维普期刊数据库

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Pillar design and coal burst experience in Utah Book Cliffs longwall operations

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International Journal of Mining Science and Technology 2021年第1期31卷 33-41页

作者： Christopher Mark michael gauna Mine Safety and Health Administration Technical Support PittsburghPA 15236USA

Longwall mining has existed in Utah for more than half a *** of this mining occurred at depths of cover that significantly exceed those encountered by most other US longwall *** cover causes high ground stress,which can combine with geology to create a coal burst *** every longwall mine operating within the Utah’s Book Cliffs coalfield has been affected by coal *** design has been a key component in the burst control strategies employed by mines in the Book ***,most longwall mines employed double-use two-entry yield pillar ***-use signifies that the gate system serves first as the headgate,and then later serves as the tailgate for the adjacent *** the 1996 burst fatality at the Aberdeen Mine,the inter-panel barrier design was *** this layout,a wide barrier pillar protects each longwall panel from the previously mined panel,and each gate system is used just *** paper documents the deep cover longwall mining conducted with each type of pillar design,together with the associated coal burst *** of the six longwall mining complexes in the Book Cliffs having a coal burst history is described on a panel-by-panel *** analysis shows that where the mining depth exceeded 450 m,each design has been employed for about 38000 total m of longwall panel *** 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 *** 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.

关键词： Longwall Ground control Coal burst Pillar design Yield pillar

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维普期刊数据库

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Preventing roof fall fatalities during pillar recovery:A ground control success story

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International Journal of Mining Science and Technology 2017年第1期27卷 107-113页

作者： Mark Christopher gauna michael MSHA Pittsburgh Safety and Health Technology CenterPittsburghPA 15236USA

For decades, pillar recovery accounted for a quarter of all roof fall fatalities in underground coal *** showed that a miner on a pillar recovery section was at least three times more likely to be killed by a roof fall than other coal miners. Since 2007, however, there has been just one fatal roof fall on a pillar line. This paper describes the process that resulted in this historic achievement. It covers both the key research findings and the ways in which those insights, beginning in the early 2000 s, were implemented in mining practice. One key finding was that safe pillar recovery requires both global and local *** stability is addressed primarily through proper pillar design, and became a major focus after the2007 Crandall Canyon mine disaster. But the most significant improvements resulted from detailed studies that showed that local stability, defined as roof control in the immediate work area, could be achieved with three interventions:(1) leaving an engineered final stump, rather than extracting the entire pillar,(2) enhancing roof bolt support, particularly in intersections, and(3) increasing the use of mobile roof supports(MRS). A final component was an emphasis on better management of pillar recovery *** included a focus on worker positioning, as well as on the pillar and lift sequences, MRS operations,and hazard identification. As retreat mines have incorporated these elements into their roof control plans,it has become clear that pillar recovery is not ‘‘inherently unsafe." The paper concludes with a discussion of the challenges that remain, including the problems of rib falls and coal bursts.

关键词： Retreat mining Roof support Room-and-pillar Ground control

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维普期刊数据库

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Evaluating the risk of coal bursts in underground coal mines

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International Journal of Mining Science and Technology 2016年第1期26卷 47-52页

作者： Mark Christopher gauna michael Pittsburgh Safety and Health Technology Center Mine Safety and Health Administration (MSHA)

Coal bursts involve the sudden,violent ejection of coal or rock into the mine workings. They are almost always accompanied by a loud noise,like an explosion,and ground vibration. Bursts are a particular hazard for miners because they typically occur without warning. Despite decades of research,the sources and mechanics of these events are not well understood,and therefore they are difficult to predict and control. Experience has shown,however,that certain geologic and mining factors are associated with an increased likelihood of a coal burst. A coal burst risk assessment consists of evaluating the degree to which these risk factors are present,and then identifying appropriate control measures to mitigate the hazard. This paper summarizes the U.S. and international experience with coal bursts,and describes the known risk factors in detail. It includes a framework that can be used to guide the risk assessment process.

关键词： Underground miningCoalCoal burstMine safetyGround control

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维普期刊数据库

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