The objective of this paper is to study the behavior of a low thick and low depth coal seam and the overburden rock mass. The mining method is room and pillar in retreat and partial pillar recovery. The excavation met...The objective of this paper is to study the behavior of a low thick and low depth coal seam and the overburden rock mass. The mining method is room and pillar in retreat and partial pillar recovery. The excavation method is conventional drill and blast because of the small production. The partial pillar recovery is about 30% of the previous pillar size, 7 m × 7 m. The roof displacement was monitored during retreat operation; the surface movement was also monitored. The effect of the blasting vibration on the final pillar strength had been considered. Due to blasting, the pillar reduced about 20%. The consequence is more pillar deformation and roof vertical displacement. The pillar retreat and ground movement were simulated in a three-dimensional numerical model. This model was created to predict the surface subsidence and compare to the subsidence measured. This study showed that the remaining pillar and low seam reduce the subsidence that was predicted with conventional methods.展开更多
When roadways are constructed above or adjacent to heavily mined regions, the ground subsidence caused by pillar collapse inflicts severe damage on these roadways. In this study, some surface subsidence events were fi...When roadways are constructed above or adjacent to heavily mined regions, the ground subsidence caused by pillar collapse inflicts severe damage on these roadways. In this study, some surface subsidence events were first reviewed to present roof caving characteristics caused by pillar failure. The bearing characteristic and failure pattern of a single pillar with or without effect of discontinuity were further numerically simulated using distinct element code(3 DEC). It was found that the spalling of pillar or slippage of discontinuity would damage the bearing capacity of pillar during the failure process. The stress at the pillar core could be greater than uniaxial compressive strength of the pillar. However, when a discontinuity runs through a pillar, the slippage of discontinuity would significantly degrade the bearing capacity of the pillar. In pillar support system, if any pillar unexpectedly degrades or loses its bearing capacity, the load transferred from the degraded pillar acts on neighboring pillars, and the shear force also increases at relevant positions. However, the roof cutting and surface subsidence characteristics would perform in different patterns. In some cases, surface subsides slowly;in the worst scenario, shock bump may be induced by pillar and roof collapse.展开更多
Mine Plant 2 is a part of the Ostrava-Karvina Coal District (OKD) that is located in the Czech part of the Upper Silesian Basin. The first coal was exhausted from Mine Plant 2 in 1968. The most used method of mining s...Mine Plant 2 is a part of the Ostrava-Karvina Coal District (OKD) that is located in the Czech part of the Upper Silesian Basin. The first coal was exhausted from Mine Plant 2 in 1968. The most used method of mining so far in this area has been strike longwall mining with controlled caving. Due to extensive changes in the surface, which occur as a consequence of deep mining by the method of longwall mining with controlled caving, it is not possible to use this method in densely populated areas. At the present time, therefore, the trial operation of a new mining method called room and pillar is carried out. The method was chosen with the aim to minimize subsidence and deformations of the surface. The room and pillar mining method has never been used before in the conditions of the OKR, therefore it is necessary to prove the real effect of mining by this method on the surface. For this purpose, a surface observation station was designed, consisting of 36 surface points. The position and height of all points of the observation station is determined in stages three times a year.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
Catastrophic sesmic events, such as a sudden collapse of open pits and underground excavations,as well as a vast surface subsidence induced by mining activities, present serious dangers to the modem infrastructure . I...Catastrophic sesmic events, such as a sudden collapse of open pits and underground excavations,as well as a vast surface subsidence induced by mining activities, present serious dangers to the modem infrastructure . In fact these "sudden" events are the result of long-term preparatory processes, which are occurring in mine pillars and ambient rock.The kinetic approach was proposed for the descripiton of the preparatory process.The process presents a stochastic accumulation of defects in rock caused by a long-term redistribution of stress-strain in an ambient rock massif. Case studies related to mining activities at Zhezkazgan copper mines, Rep. kazakhstan, were coni\sidered.As was shown the seismic monitoring is a good method for forecasting catastrophic caving and surface subsidence.展开更多
According to the characteristic of huge thick loose layer in Huainan mining area, based on the measured data, the correlation between the relative parameters of coal pillar setting and the ratio of loose layer thickne...According to the characteristic of huge thick loose layer in Huainan mining area, based on the measured data, the correlation between the relative parameters of coal pillar setting and the ratio of loose layer thickness to mining depth in Huainan mining area under the mining condition of huge thick loose layer was mainly studied by using regression analysis method, and corresponding mathematical models were established and analyzed. It makes a theoretical supplement for the the analysis and research of mining subsidence rules in Huainan mining area under the condition of huge thick loose layer.展开更多
文摘The objective of this paper is to study the behavior of a low thick and low depth coal seam and the overburden rock mass. The mining method is room and pillar in retreat and partial pillar recovery. The excavation method is conventional drill and blast because of the small production. The partial pillar recovery is about 30% of the previous pillar size, 7 m × 7 m. The roof displacement was monitored during retreat operation; the surface movement was also monitored. The effect of the blasting vibration on the final pillar strength had been considered. Due to blasting, the pillar reduced about 20%. The consequence is more pillar deformation and roof vertical displacement. The pillar retreat and ground movement were simulated in a three-dimensional numerical model. This model was created to predict the surface subsidence and compare to the subsidence measured. This study showed that the remaining pillar and low seam reduce the subsidence that was predicted with conventional methods.
基金Projects(51838001, 51878070, 51904101) supported by the National Natural Science Foundation of ChinaProject(2019SK2171) supported by the Key Research and Development Program of Hunan Province, ChinaProject(kfj190402) supported by the Open Fund of Engineering Research Center of Catastrophic Prophylaxis and Treatment of Road & Traffic Safety of Ministry of Education(Changsha University of Science & Technology), China。
文摘When roadways are constructed above or adjacent to heavily mined regions, the ground subsidence caused by pillar collapse inflicts severe damage on these roadways. In this study, some surface subsidence events were first reviewed to present roof caving characteristics caused by pillar failure. The bearing characteristic and failure pattern of a single pillar with or without effect of discontinuity were further numerically simulated using distinct element code(3 DEC). It was found that the spalling of pillar or slippage of discontinuity would damage the bearing capacity of pillar during the failure process. The stress at the pillar core could be greater than uniaxial compressive strength of the pillar. However, when a discontinuity runs through a pillar, the slippage of discontinuity would significantly degrade the bearing capacity of the pillar. In pillar support system, if any pillar unexpectedly degrades or loses its bearing capacity, the load transferred from the degraded pillar acts on neighboring pillars, and the shear force also increases at relevant positions. However, the roof cutting and surface subsidence characteristics would perform in different patterns. In some cases, surface subsides slowly;in the worst scenario, shock bump may be induced by pillar and roof collapse.
文摘Mine Plant 2 is a part of the Ostrava-Karvina Coal District (OKD) that is located in the Czech part of the Upper Silesian Basin. The first coal was exhausted from Mine Plant 2 in 1968. The most used method of mining so far in this area has been strike longwall mining with controlled caving. Due to extensive changes in the surface, which occur as a consequence of deep mining by the method of longwall mining with controlled caving, it is not possible to use this method in densely populated areas. At the present time, therefore, the trial operation of a new mining method called room and pillar is carried out. The method was chosen with the aim to minimize subsidence and deformations of the surface. The room and pillar mining method has never been used before in the conditions of the OKR, therefore it is necessary to prove the real effect of mining by this method on the surface. For this purpose, a surface observation station was designed, consisting of 36 surface points. The position and height of all points of the observation station is determined in stages three times a year.
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Catastrophic sesmic events, such as a sudden collapse of open pits and underground excavations,as well as a vast surface subsidence induced by mining activities, present serious dangers to the modem infrastructure . In fact these "sudden" events are the result of long-term preparatory processes, which are occurring in mine pillars and ambient rock.The kinetic approach was proposed for the descripiton of the preparatory process.The process presents a stochastic accumulation of defects in rock caused by a long-term redistribution of stress-strain in an ambient rock massif. Case studies related to mining activities at Zhezkazgan copper mines, Rep. kazakhstan, were coni\sidered.As was shown the seismic monitoring is a good method for forecasting catastrophic caving and surface subsidence.
文摘According to the characteristic of huge thick loose layer in Huainan mining area, based on the measured data, the correlation between the relative parameters of coal pillar setting and the ratio of loose layer thickness to mining depth in Huainan mining area under the mining condition of huge thick loose layer was mainly studied by using regression analysis method, and corresponding mathematical models were established and analyzed. It makes a theoretical supplement for the the analysis and research of mining subsidence rules in Huainan mining area under the condition of huge thick loose layer.
