The rock mass failure induced by deep mining exhibits pronounced spatial heterogeneity and diverse mechanisms,with its microseismic responses serving as effective indicators of regional failure evolution and instabili...The rock mass failure induced by deep mining exhibits pronounced spatial heterogeneity and diverse mechanisms,with its microseismic responses serving as effective indicators of regional failure evolution and instability mechanisms.Focusing on the Level VI stope sublayers in the Jinchuan#2 mining area,this study constructs a 24-parameter index system encompassing time-domain features,frequency-domain features,and multifractal characteristics.Through manifold learning,clustering analysis,and hybrid feature selection,15 key indicators were extracted to construct a classification framework for failure responses.Integrated with focal mechanism inversion and numerical simulation,the failure patterns and corresponding instability mechanisms across different structural zones were further identified.The results reveal that multiscale microseismic characteristics exhibit clear regional similarities.Based on the morphological features of radar plots derived from the 15 indicators,acoustic responses were classified into four typical types,each reflecting distinct local failure mechanisms,stress conditions,and plastic zone evolution.Moreover,considering dominant instability factors and rupture modes,four representative rock mass instability models were proposed for typical failure zones within the stope.These findings provide theoretical guidance and methodological support for hazard prediction,structural optimization,and disturbance control in deep metal mining areas.展开更多
Severe shield jamming events have been reported during excavation of Uluabat tunnel through adverse geological conditions, which resulted in several stoppages at advancing a single shielded tunnel boring machine(TBM)....Severe shield jamming events have been reported during excavation of Uluabat tunnel through adverse geological conditions, which resulted in several stoppages at advancing a single shielded tunnel boring machine(TBM). To study the jamming mechanism, three-dimensional(3D) simulation of the machine and surrounding ground was implemented using the finite difference code FLAC3D. Numerical analyses were performed for three sections along the tunnel with a higher risk for entrapment due to the combination of overburden and geological conditions. The computational results including longitudinal displacement contours and ground pressure profiles around the shield allow a better understanding of ground behavior within the excavation. Furthermore, they allow realistically assessing the impact of adverse geological conditions on shield jamming. The calculated thrust forces, which are required to move the machine forward, are in good agreement with field observations and measurements. It also proves that the numerical analysis can effectively be used for evaluating the effect of adverse geological environment on TBM entrapments and can be applied to prediction of loads on the shield and preestimating of the required thrust force during excavation through adverse ground conditions.展开更多
In the Kaiping Coal field,mining of five coal seams,located within 80 m in the Kailuan Group,#5,#7,#8,#9 and#12 coal seam,is difficult due to small interburden thickness,concentrated stress distributions,high coal sea...In the Kaiping Coal field,mining of five coal seams,located within 80 m in the Kailuan Group,#5,#7,#8,#9 and#12 coal seam,is difficult due to small interburden thickness,concentrated stress distributions,high coal seam metamorphism,and complex geological conditions.By using the ZTR12 geological penetration radar(GPR)survey combined with borehole observations,the overburden caving due to mining of the five coals seams was measured.The development characteristics of full-cover rock fractures after mining were obtained from the GPR scan,which provides a measurement basis for the control of rock strata in close multiple coal seam mining.For the first time,it was found that the overburden caving pattern shows a periodic triangular caved characteristic.Furthermore,it is proposed that an upright triangular collapsed pile masonry and an inverted triangular with larger fragments piled up alternately appear in the lower gob.The research results show that the roof structure formed in the gob area can support the key overlying strata,which is beneficial to ensure the integrity and stability of the upper coal seams in multiple-seam mining of close coal seams.展开更多
In underground coal mines, uncontrolled accumulation of methane and fine coal dust often leads to serious incidents such as explosion. Therefore, methane and dust dispersion in underground mines is closely monitored a...In underground coal mines, uncontrolled accumulation of methane and fine coal dust often leads to serious incidents such as explosion. Therefore, methane and dust dispersion in underground mines is closely monitored and strictly regulated. Accordingly, significant efforts have been devoted to study methane and dust dispersion in underground mines. In this study, methane emission and dust concentration are numerically investigated using a computational fluid dynamics(CFD) approach. Various possible scenarios of underground mine configurations are evaluated. The results indicate that the presence of continuous miner adversely affects the air flow and leads to increased methane and dust concentrations.Nevertheless, it is found that such negative effect can be minimized or even neutralized by operating the scrubber fan in suction mode. In addition, it was found that the combination of scrubber fan in suction mode and brattice results in the best performance in terms of methane and dust removal from the mining face.展开更多
Ground movements due to longwall mining operations have the potential to damage the hydrological balance within as well as outside the mine permit area in the form of increased surface ponding and changes to hydrogeol...Ground movements due to longwall mining operations have the potential to damage the hydrological balance within as well as outside the mine permit area in the form of increased surface ponding and changes to hydrogeological properties. Recently, the Office of Surface Mining, Reclamation and Enforcement(OSMRE) in the USA, has completed a public comment period on a newly proposed rule for the protection of streams and groundwater from adverse impacts of surface and underground mining operations(80 FR 44435). With increased community and regulatory focus on mining operations and their potential to adversely affect streams and groundwater, now there is a greater need for better prediction of the possible effects mining has on both surface and subsurface bodies of water. With mining induced stress and strain within the overburden correlated to changes in the hydrogeological properties of rock and soil, this paper investigates the evaluation of the hydrogeological system within the vicinity of an underground mining operation based on strain values calculated through a surface deformation prediction model. Through accurate modeling of the pre- and post-mining hydrogeological system, industry personnel can better depict mining induced effects on surface and subsurface bodies of water aiding in the optimization of underground extraction sequences while maintaining the integrity of water resources.展开更多
A proper control and management of dust dispersion is essential to ensure safe and productive underground working environment. Brattice installation to direct the flow from main shaft to the mining face was found to b...A proper control and management of dust dispersion is essential to ensure safe and productive underground working environment. Brattice installation to direct the flow from main shaft to the mining face was found to be the most effective method to disperse dust particle away from the mining face. However,it limits the movement and disturbs the flexibility of the mining fleets and operators at the tunnel. This study proposes a hybrid brattice system- a combination of a physical brattice together with suitable and flexible directed and located air curtains- to mitigate dust dispersion from the mining face and reduce dust concentration to a safe level for the working operators. A validated three-dimensional computational fluid dynamic model utilizing Eulerian–Lagrangian approach is employed to track the dispersion of dust particle. Several possible hybrid brattice scenarios are evaluated with the objective to improve dust management in underground mine. The results suggest that implementation of hybrid brattice is beneficial for the mining operation: up to three times lower dust concentration is achieved as compared to that of the physical brattice without air curtain.展开更多
The broad objective of this research was to improve current surface mining practices and reduce negative environmental impact of overburden removal in West Virginia(WV).The specific objectives were to(i)compare conven...The broad objective of this research was to improve current surface mining practices and reduce negative environmental impact of overburden removal in West Virginia(WV).The specific objectives were to(i)compare conventional surface mining method(drilling,blasting,digging,and loading)to a surface miner(SM)method,and(ii)apply the analytical hierarchy process(AHP)to help select the optimal mining method based on production,cost and environmental criteria.The design and the procedures used in this research involve five interrelated modules:(i)rock properties of overburden in WV,(ii)drilling and blasting,(iii)digging and loading,(iv)SM method,and(v)comparative analysis and selection of the optimal mining method by AHP.Results of this research indicate that application of SM method would yield higher cost of overburden removal than conventional mining methods in rocks with a high unconfined compressive strength and abrasivity.A significant advantage of SM method,where applicable,is the elimination of the negative environmental impacts associated with blasting.展开更多
The production cycle of open-cast coal mines generally in eludes drilling, blasting, loading, hauling and coal preparation activities. Individual optimization of these activities does not mean that the whole system is...The production cycle of open-cast coal mines generally in eludes drilling, blasting, loading, hauling and coal preparation activities. Individual optimization of these activities does not mean that the whole system is optimized. This paper proposes a cost model considering all activities in mining cycle and system-wide approach to minimize the total mining cost of bench production. Since the fragmentation size and blast-hole diameter are linked to all activities of mining system, they are considered as decision variables in the problem form ul at io n. The operatio n costs are then minimized by using the evolutionary algorithm. Moreover, the impact of the change in the explosive price, and the hourly unit cost of equipment on total mining cost is quantified by sensitivity analysis. A case study is implemented to demonstrate the developed model.展开更多
Shallow seam coal field has the largest coal reserve in China. Mining in shallow depth causes serious problems, and subsurface dewatering is a major issue. In this paper, the physical simulating models were prepared t...Shallow seam coal field has the largest coal reserve in China. Mining in shallow depth causes serious problems, and subsurface dewatering is a major issue. In this paper, the physical simulating models were prepared to study overburden movement and aquiclude stability in the shallow seam mining of Yushuwan Coalfield, China. According to the characteristic of clay aquiclude and bedrock in the overburden, the proper simulation materials for simulating the plastic clay aquiclude layers and brittle bedrock layers were determined by the stress-strain tests and hydrophilic tests. The physical simulating models of solid medium and two phases of solid-liquid medium were carried out to simulate the failure and caving process of the roof and overburden, as well as the subsurface water seeping. Based on the simulation, it was found that the movement of clay aquiclude follows the movement of the underlying bedrock layers. The stability of aquiclude is mainly affected by cracks in fracture zone. The tests also showed that the best way to control the stability of aquiclude is to reduce the subsiding gradient, and there is a possibility of ground water conservation under longwall mining in Yushuwan Mine. This research provides a foundation for further study on mining dewatering and water conservation.展开更多
Equipment plays an important role in open pit mining industry and its cost competence at efficient operation and maintenance techniques centered on reliability can lead to significant cost reduction.The application of...Equipment plays an important role in open pit mining industry and its cost competence at efficient operation and maintenance techniques centered on reliability can lead to significant cost reduction.The application of optimal maintenance process was investigated for minimizing the equipment breakdowns and downtimes in Sungun Copper Mine.It results in the improved efficiency and productivity of the equipment and lowered expenses as well as the increased profit margin.The field operating data of 10 trucks are used to estimate the failure and maintenance profile for each component,and modeling and simulation are accomplished by using reliability block diagram method.Trend analysis was then conducted to select proper probabilistic model for maintenance profile.Then reliability of the system was evaluated and importance of each component was computed by weighted importance measure method.This analysis led to identify the items with critical impact on availability of overall equipment in order to prioritize improvement decisions.Later,the availability of trucks was evaluated using Monte Carlo simulation and it is revealed that the uptime of the trucks is around 11000 h at 12000 operation hours.Finally,uncertainty analysis was performed to account for the uncertainty sources in data and models.展开更多
Longwall mining has a significant influence on gas wells located within longwall chain pillars.Subsurface subsidence and abutment pressure induced by longwall mining can cause excessive stresses and deformations in ga...Longwall mining has a significant influence on gas wells located within longwall chain pillars.Subsurface subsidence and abutment pressure induced by longwall mining can cause excessive stresses and deformations in gas well casings.If the gas well casings are compromised or ruptured,natural gas could migrate into the mine workings,potentially causing a fire or explosion.By the current safety regulations,the gas wells in the chain pillars have to be either plugged or protected by adequate coal pillars.The current regulations for gas well pillar design are based on the 1957 Pennsylvania gas well pillar study.The study provided guidelines for gas well pillars by considering their support area and overburden depth as well as the location of the gas wells within the pillars.As the guidelines were developed for room-andpillar mining under shallow cover,they are no longer applicable to modern longwall coal mining,particularly,under deep cover.Gas well casing of failures have occurred even though the chain pillars for the gas wells met the requirements by the 1957 study.This study,conducted by the National Institute for Occupational Safety and Health(NIOSH),presents seven cases of conventional gas wells penetrating through longwall chain pillars in the Pittsburgh Coal Seam.The study results indicate that overburden depth and pillar size are not the only determining factors for gas well stability.The other important factors include subsurface ground movement,overburden geology,weak floor,as well as the type of the construction of gas wells.Numerical modeling was used to model abutment pressure,subsurface deformations,and the response of gas well casings.The study demonstrated that numerical models are able to predict with reasonable accuracy the subsurface deformations in the overburden above,within,and below the chain pillars,and the potential location and modes of gas well failures,thereby providing a more quantifiable approach to assess the stability of the gas wells in longwall chain pillars.展开更多
Differential Interferometric Synthetic Aperture Radar(DInSAR),a satellite-based remote sensing technique,has application for monitoring subsidence with high resolution over short periods.DInSAR uses radar images to me...Differential Interferometric Synthetic Aperture Radar(DInSAR),a satellite-based remote sensing technique,has application for monitoring subsidence with high resolution over short periods.DInSAR uses radar images to measure centimeter-level surface displacements.In the images,ground resolution can be relatively high,with each data point(pixel)representing the average displacement over an area of several square meters.The image data are acquired regularly which allows subsidence to be monitored sequentially over short periods;imaging periods typically range from weeks to months.Monitoring subsidence over short periods with high spatial resolution has potential to provide insight into the dynamics of subsidence and into relationships between mine advance and subsidence.In this study,for three longwall mines in the western United States,initial subsidence occurring at the start of longwall advance is quantified over short periods(12–72 days).C-band interferometric wide swath Synthetic Aperture Radar(SAR)images from the Sentinel satellites are used to quantify the subsidence.Overall,the data show initial development of subsidence,expansion of the subsidence trough,and the advance of subsidence in the direction of mining.展开更多
Most, if not all longwall gob areas accumulate explosive methane-air mixtures that pose a deadly hazard to miners. Numerous mine explosions have originated from explosive gas zones(EGZs) in the longwall gob. Since 201...Most, if not all longwall gob areas accumulate explosive methane-air mixtures that pose a deadly hazard to miners. Numerous mine explosions have originated from explosive gas zones(EGZs) in the longwall gob. Since 2010, researchers at the Colorado School of Mines(CSM) have studied EGZ formation in longwall gobs under two long-term research projects funded by the National Institute for Occupational Safety and Health. Researchers used computational fluid dynamics along with in-mine measurements. For the first time, they demonstrated that EGZs form along the fringe areas between the methane-rich atmospheres and the fresh air ventilated areas along the working face and present an explosion and fire hazard to mine workers. In this study, researchers found that, for progressively sealed gobs, a targeted injection of nitrogen from the headgate and tailgate, along with a back return ventilation arrangement, will create a dynamic seal of nitrogen that effectively separates the methane zone from the face air and eliminates the EGZs to prevent explosions. Using this form of nitrogen injection to create dynamic seals should be a consideration for all longwall operators.展开更多
This paper presents the results of numerical simulations carried out to confirm the influence of former mining activities on deformation of the mining terrain.The assessment of deformation changes was carried out with...This paper presents the results of numerical simulations carried out to confirm the influence of former mining activities on deformation of the mining terrain.The assessment of deformation changes was carried out with the use of FLAC3 D program based on the finite difference method.Numerical calculations were carried out for the example of actual mining operations in seams 703/1-2 and 707/2 of‘‘Marcel"Coal Mine.Taking into account the influence of the model’s plastic features and the so-called activation of a higher occurring seam in conducted simulations enabled obtaining a very good description of the measured subsidence.Based on the results one may state that numerical model can be used to assess the influence of former mining activities and the direction of conducted exploitation on deformations of the mining terrain.These factors are not recognized by geometric-integral theories commonly used for predicting the influence of mining operations on the surface.The results presented in this paper confirm that the applied method of simulating the phenomenon of reactivation of post-mining goafs is correct.展开更多
The paper presents the influence of varying immediate roof thickness on the lower strong roof strata movement and failure pattern in longwall coal mining with large mining height. The investigation is based on 58 geol...The paper presents the influence of varying immediate roof thickness on the lower strong roof strata movement and failure pattern in longwall coal mining with large mining height. The investigation is based on 58 geological drill holes and hydraulic shield pressure measurements around the longwall Panel 42105 of the Buertai Mine in Inner Mongolia Autonomous Region, China. The longwall Panel 42105 is characterized by relatively soft immediate roof strata of varying thickness superposed by strong strata,herein defined as lower strong roof. A voussoir beam model is adopted to interpret the structural movement of the lower strong roof strata and shield pressure measurements. It is shown that when the immediate roof is relatively thick, the broken overlying lower strong roof tends to form a stable voussoir beam with previously broken layer, thus not exerting high pressure on the hydraulic shield and working face. When the immediate roof is relatively thin, the broken overlying lower strong roof tends to behave as a cantilever beam, thus exerting higher pressure on the hydraulic shield and working face. Comparison of model predictions with measured time-weighted average shield pressure(TWAP) shows good agreement.展开更多
Wellbore instability is reported frequently as one of the most significant incidents during drilling operations.Analysis of wellbore instability includes estimation of formation mechanical properties and the state of ...Wellbore instability is reported frequently as one of the most significant incidents during drilling operations.Analysis of wellbore instability includes estimation of formation mechanical properties and the state of in situ stresses.In this analysis,the only controllable parameter during drilling operation is the mud weight.If the mud weight is larger than anticipated,the mud will invade into the formation,causing tensile failure of the formation.On the other hand,a lower mud weight can result in shear failures of rock,which is known as borehole breakouts.To predict the potential for failures around the wellbore during drilling,one should use a failure criterion to compare the rock strength against induced tangential stresses around the wellbore at a given mud pressure.The Mohr–Coulomb failure criterion is one of the commonly accepted criteria for estimation of rock strength at a given state of stress.However,the use of other criteria has been debated in the literature.In this paper,Mohr–Coulomb,Hoek–Brown and Mogi–Coulomb failure criteria were used to estimate the potential rock failure around a wellbore located in an onshorefield of Iran.The log based analysis was used to estimate rock mechanical properties of formations and state of stresses.The results indicated that amongst different failure criteria,the Mohr–Coulomb criterion underestimates the highest mud pressure required to avoid breakouts around the wellbore.It also predicts a lower fracture gradient pressure.In addition,it was found that the results obtained from Mogi–Coulomb criterion yield a better comparison with breakouts observed from the caliper logs than that of Hoek–Brown criterion.It was concluded that the Mogi–Coulomb criterion is a better failure criterion as it considers the effect of the intermediate principal stress component in the failure analysis.展开更多
The purpose of this research was to develop a new approach in determination of overhaul and maintenance cost of loading equipment in surface mining. Two statistical models including univariate exponential regression (...The purpose of this research was to develop a new approach in determination of overhaul and maintenance cost of loading equipment in surface mining. Two statistical models including univariate exponential regression (UER) and multivariate linear regression (MLR) were used in this study. Loading equipment parameters such as bucket capacity, machine weight, engine power, boom length, digging depth, and dumping height were considered as variables. The results obtained by models and mean absolute error rate indicate that these models can be applied as the useful tool in determination of overhaul and maintenance cost of loading equipment. The results of this study can be used by the decision-makers for the specific surface mining operations.展开更多
Coal seams in Tashan Mine of Datong Coal Group in China average 15 m thick and have been mined by the top coal caving longwall mining method of large mining height. Mining height was 3.8 m and the top coal caving heig...Coal seams in Tashan Mine of Datong Coal Group in China average 15 m thick and have been mined by the top coal caving longwall mining method of large mining height. Mining height was 3.8 m and the top coal caving height was 11.2 m. The gateroad pillar between panels was 38 m. During retreat mining,serious bumps occurred in the gateroads on both sides of the pillar affecting safety production. Therefore,pillarless mining was experimented. Using numerical modeling and comparative study of cases of similar mining condition,it was decided to employ a 6 m wide pillar,rather than the previous 38 m wide pillar.Support system for the gateroads was designed and implemented. During gateroad development,pillar failure conditions and entry deformation were monitored. Hydraulic fracturing method was employed to cut off the K3 sandstone along the entry rib so as to reduce the abutment pressure induced during retreat mining. Support reinforcement method combining grouting and advanced reinforcement methods was proposed to insure stable gateroad ahead of mining. Methane drainage and nitrogen injection were implemented to eliminate hazards associated with mine fire and spontaneous combustion. Since the development of gateroad has just completed,and retreat mining has not begun,the effectiveness of the proposed methods is unknown at this point. However,monitoring will continue until after mining.The results will be published in a separate paper.展开更多
‘‘Web ground control"(web GC) provides users with instantaneous access to mine design applications anywhere, at any time, through a web browser.Utilizing a web-based multiple-tier architecture, users are able t...‘‘Web ground control"(web GC) provides users with instantaneous access to mine design applications anywhere, at any time, through a web browser.Utilizing a web-based multiple-tier architecture, users are able to easily access ground control designs, perform on-demand calculations in the field, as well as facilitate project collaborations across multiple users, devices, and operating systems.Currently, the web GC platform contains five ground control related design applications previously developed and distributed by the US National Institute of Occupational Safety and Health(NIOSH), that is, analysis of roof bolt stability(ARBS), analysis of longwall pillar stability(ALPS), analysis of retreat mining stability(ARMPS), analysis of retreat mining stability–highwall mining(ARMPS-HWM), and analysis of horizontal stress in mining(AHSM).With respect to design decisions made by the web GC development team, the web GC platform will be able to further integrate future mine design applications providing the mining industry with one of a kind umbrella suite of ground control related software available at ones fingertips.The following paper provides a detailed overview on the current state of the web GC platform with discussions ranging from back-end database development and design to the front-end user-platform interface.Based on current progress in platform development as well as beta testing results, the web GC platform is scheduled for release in the fall of 2018.展开更多
Directive(EU)2017/164 establishes a fourth list of indicative occupational exposure limit values(IOELVs)to protect workers from risks of exposure to hazardous chemicals.It states that in underground mining and tunnell...Directive(EU)2017/164 establishes a fourth list of indicative occupational exposure limit values(IOELVs)to protect workers from risks of exposure to hazardous chemicals.It states that in underground mining and tunnelling,Member States may benefit from a transitional period regarding IOELVs for nitrogen monoxide,nitrogen dioxide,and carbon monoxide,during which the existing established IOELVs may be applied.The European Advisory Committee on Health and Safety at Work questions the technical feasibility of the proposed IOELVs in underground mining(CO,NO and NO2)and tunnelling(NO and NO2).Challenges arise concerning the availability of measurement methodologies for compliance with proposed IOELVs(NO2)in underground mining and tunnelling environments.展开更多
基金financial support from the Distinguished Youth Funds of the National Natural Science Foundation of China(No.52425403)the Hunan Province Graduate Research Innovation Project of China(No.CX20230168)。
文摘The rock mass failure induced by deep mining exhibits pronounced spatial heterogeneity and diverse mechanisms,with its microseismic responses serving as effective indicators of regional failure evolution and instability mechanisms.Focusing on the Level VI stope sublayers in the Jinchuan#2 mining area,this study constructs a 24-parameter index system encompassing time-domain features,frequency-domain features,and multifractal characteristics.Through manifold learning,clustering analysis,and hybrid feature selection,15 key indicators were extracted to construct a classification framework for failure responses.Integrated with focal mechanism inversion and numerical simulation,the failure patterns and corresponding instability mechanisms across different structural zones were further identified.The results reveal that multiscale microseismic characteristics exhibit clear regional similarities.Based on the morphological features of radar plots derived from the 15 indicators,acoustic responses were classified into four typical types,each reflecting distinct local failure mechanisms,stress conditions,and plastic zone evolution.Moreover,considering dominant instability factors and rupture modes,four representative rock mass instability models were proposed for typical failure zones within the stope.These findings provide theoretical guidance and methodological support for hazard prediction,structural optimization,and disturbance control in deep metal mining areas.
基金Alexander von Humboldt-Foundation (AvH) for the financial support as a research fellowthe financial support of the Scientific and Technological Research Council of Turkey (TüB_ITAK) under Project No. MAG-114M568
文摘Severe shield jamming events have been reported during excavation of Uluabat tunnel through adverse geological conditions, which resulted in several stoppages at advancing a single shielded tunnel boring machine(TBM). To study the jamming mechanism, three-dimensional(3D) simulation of the machine and surrounding ground was implemented using the finite difference code FLAC3D. Numerical analyses were performed for three sections along the tunnel with a higher risk for entrapment due to the combination of overburden and geological conditions. The computational results including longitudinal displacement contours and ground pressure profiles around the shield allow a better understanding of ground behavior within the excavation. Furthermore, they allow realistically assessing the impact of adverse geological conditions on shield jamming. The calculated thrust forces, which are required to move the machine forward, are in good agreement with field observations and measurements. It also proves that the numerical analysis can effectively be used for evaluating the effect of adverse geological environment on TBM entrapments and can be applied to prediction of loads on the shield and preestimating of the required thrust force during excavation through adverse ground conditions.
基金The research is supported by National Key R&D Program of China(No.2017YFC060300204)National Natural Science Foundation of China(No.52074293)+2 种基金Hebei Province Natural Science Foundation of China(No.E2020402041)Yue Qi Young Scholar Project,CUMTB and Yue Qi Distinguished Scholar Project(No.800015Z1138)China University of Mining&Technology,Beijing.
文摘In the Kaiping Coal field,mining of five coal seams,located within 80 m in the Kailuan Group,#5,#7,#8,#9 and#12 coal seam,is difficult due to small interburden thickness,concentrated stress distributions,high coal seam metamorphism,and complex geological conditions.By using the ZTR12 geological penetration radar(GPR)survey combined with borehole observations,the overburden caving due to mining of the five coals seams was measured.The development characteristics of full-cover rock fractures after mining were obtained from the GPR scan,which provides a measurement basis for the control of rock strata in close multiple coal seam mining.For the first time,it was found that the overburden caving pattern shows a periodic triangular caved characteristic.Furthermore,it is proposed that an upright triangular collapsed pile masonry and an inverted triangular with larger fragments piled up alternately appear in the lower gob.The research results show that the roof structure formed in the gob area can support the key overlying strata,which is beneficial to ensure the integrity and stability of the upper coal seams in multiple-seam mining of close coal seams.
基金financial support from McGill University-Canada and NSERC-Discovery Grant RGPIN-2015-03945
文摘In underground coal mines, uncontrolled accumulation of methane and fine coal dust often leads to serious incidents such as explosion. Therefore, methane and dust dispersion in underground mines is closely monitored and strictly regulated. Accordingly, significant efforts have been devoted to study methane and dust dispersion in underground mines. In this study, methane emission and dust concentration are numerically investigated using a computational fluid dynamics(CFD) approach. Various possible scenarios of underground mine configurations are evaluated. The results indicate that the presence of continuous miner adversely affects the air flow and leads to increased methane and dust concentrations.Nevertheless, it is found that such negative effect can be minimized or even neutralized by operating the scrubber fan in suction mode. In addition, it was found that the combination of scrubber fan in suction mode and brattice results in the best performance in terms of methane and dust removal from the mining face.
基金sponsored by the Appalachian Research Initiative for Environmental Science(ARIES)
文摘Ground movements due to longwall mining operations have the potential to damage the hydrological balance within as well as outside the mine permit area in the form of increased surface ponding and changes to hydrogeological properties. Recently, the Office of Surface Mining, Reclamation and Enforcement(OSMRE) in the USA, has completed a public comment period on a newly proposed rule for the protection of streams and groundwater from adverse impacts of surface and underground mining operations(80 FR 44435). With increased community and regulatory focus on mining operations and their potential to adversely affect streams and groundwater, now there is a greater need for better prediction of the possible effects mining has on both surface and subsurface bodies of water. With mining induced stress and strain within the overburden correlated to changes in the hydrogeological properties of rock and soil, this paper investigates the evaluation of the hydrogeological system within the vicinity of an underground mining operation based on strain values calculated through a surface deformation prediction model. Through accurate modeling of the pre- and post-mining hydrogeological system, industry personnel can better depict mining induced effects on surface and subsurface bodies of water aiding in the optimization of underground extraction sequences while maintaining the integrity of water resources.
基金financially supported by the Singapore Economic Development Board(EDB)through the Minerals Metals and Materials Technology Centre(M3TC)Research Grant R-261-501-013-414
文摘A proper control and management of dust dispersion is essential to ensure safe and productive underground working environment. Brattice installation to direct the flow from main shaft to the mining face was found to be the most effective method to disperse dust particle away from the mining face. However,it limits the movement and disturbs the flexibility of the mining fleets and operators at the tunnel. This study proposes a hybrid brattice system- a combination of a physical brattice together with suitable and flexible directed and located air curtains- to mitigate dust dispersion from the mining face and reduce dust concentration to a safe level for the working operators. A validated three-dimensional computational fluid dynamic model utilizing Eulerian–Lagrangian approach is employed to track the dispersion of dust particle. Several possible hybrid brattice scenarios are evaluated with the objective to improve dust management in underground mine. The results suggest that implementation of hybrid brattice is beneficial for the mining operation: up to three times lower dust concentration is achieved as compared to that of the physical brattice without air curtain.
基金The research work in this paper is financially supported by the West Virginia Coal and Energy Research Bureau(CERB).
文摘The broad objective of this research was to improve current surface mining practices and reduce negative environmental impact of overburden removal in West Virginia(WV).The specific objectives were to(i)compare conventional surface mining method(drilling,blasting,digging,and loading)to a surface miner(SM)method,and(ii)apply the analytical hierarchy process(AHP)to help select the optimal mining method based on production,cost and environmental criteria.The design and the procedures used in this research involve five interrelated modules:(i)rock properties of overburden in WV,(ii)drilling and blasting,(iii)digging and loading,(iv)SM method,and(v)comparative analysis and selection of the optimal mining method by AHP.Results of this research indicate that application of SM method would yield higher cost of overburden removal than conventional mining methods in rocks with a high unconfined compressive strength and abrasivity.A significant advantage of SM method,where applicable,is the elimination of the negative environmental impacts associated with blasting.
文摘The production cycle of open-cast coal mines generally in eludes drilling, blasting, loading, hauling and coal preparation activities. Individual optimization of these activities does not mean that the whole system is optimized. This paper proposes a cost model considering all activities in mining cycle and system-wide approach to minimize the total mining cost of bench production. Since the fragmentation size and blast-hole diameter are linked to all activities of mining system, they are considered as decision variables in the problem form ul at io n. The operatio n costs are then minimized by using the evolutionary algorithm. Moreover, the impact of the change in the explosive price, and the hourly unit cost of equipment on total mining cost is quantified by sensitivity analysis. A case study is implemented to demonstrate the developed model.
基金This work was financially supported by the National Natural Science Foundation of China (No.50574074)the Key Program of Sci-ence and Technology of the Ministry of Education of China (No.204183)the Program for New Century Excellent Talents in Universities of China (NCET-04-0971)
文摘Shallow seam coal field has the largest coal reserve in China. Mining in shallow depth causes serious problems, and subsurface dewatering is a major issue. In this paper, the physical simulating models were prepared to study overburden movement and aquiclude stability in the shallow seam mining of Yushuwan Coalfield, China. According to the characteristic of clay aquiclude and bedrock in the overburden, the proper simulation materials for simulating the plastic clay aquiclude layers and brittle bedrock layers were determined by the stress-strain tests and hydrophilic tests. The physical simulating models of solid medium and two phases of solid-liquid medium were carried out to simulate the failure and caving process of the roof and overburden, as well as the subsurface water seeping. Based on the simulation, it was found that the movement of clay aquiclude follows the movement of the underlying bedrock layers. The stability of aquiclude is mainly affected by cracks in fracture zone. The tests also showed that the best way to control the stability of aquiclude is to reduce the subsiding gradient, and there is a possibility of ground water conservation under longwall mining in Yushuwan Mine. This research provides a foundation for further study on mining dewatering and water conservation.
基金the support of the Maintenance Department of Mobin Co.Sungun Copper mine
文摘Equipment plays an important role in open pit mining industry and its cost competence at efficient operation and maintenance techniques centered on reliability can lead to significant cost reduction.The application of optimal maintenance process was investigated for minimizing the equipment breakdowns and downtimes in Sungun Copper Mine.It results in the improved efficiency and productivity of the equipment and lowered expenses as well as the increased profit margin.The field operating data of 10 trucks are used to estimate the failure and maintenance profile for each component,and modeling and simulation are accomplished by using reliability block diagram method.Trend analysis was then conducted to select proper probabilistic model for maintenance profile.Then reliability of the system was evaluated and importance of each component was computed by weighted importance measure method.This analysis led to identify the items with critical impact on availability of overall equipment in order to prioritize improvement decisions.Later,the availability of trucks was evaluated using Monte Carlo simulation and it is revealed that the uptime of the trucks is around 11000 h at 12000 operation hours.Finally,uncertainty analysis was performed to account for the uncertainty sources in data and models.
文摘Longwall mining has a significant influence on gas wells located within longwall chain pillars.Subsurface subsidence and abutment pressure induced by longwall mining can cause excessive stresses and deformations in gas well casings.If the gas well casings are compromised or ruptured,natural gas could migrate into the mine workings,potentially causing a fire or explosion.By the current safety regulations,the gas wells in the chain pillars have to be either plugged or protected by adequate coal pillars.The current regulations for gas well pillar design are based on the 1957 Pennsylvania gas well pillar study.The study provided guidelines for gas well pillars by considering their support area and overburden depth as well as the location of the gas wells within the pillars.As the guidelines were developed for room-andpillar mining under shallow cover,they are no longer applicable to modern longwall coal mining,particularly,under deep cover.Gas well casing of failures have occurred even though the chain pillars for the gas wells met the requirements by the 1957 study.This study,conducted by the National Institute for Occupational Safety and Health(NIOSH),presents seven cases of conventional gas wells penetrating through longwall chain pillars in the Pittsburgh Coal Seam.The study results indicate that overburden depth and pillar size are not the only determining factors for gas well stability.The other important factors include subsurface ground movement,overburden geology,weak floor,as well as the type of the construction of gas wells.Numerical modeling was used to model abutment pressure,subsurface deformations,and the response of gas well casings.The study demonstrated that numerical models are able to predict with reasonable accuracy the subsurface deformations in the overburden above,within,and below the chain pillars,and the potential location and modes of gas well failures,thereby providing a more quantifiable approach to assess the stability of the gas wells in longwall chain pillars.
基金Funding for this research was provided by the National Institute for Occupational Health and Safety(NIOSH).
文摘Differential Interferometric Synthetic Aperture Radar(DInSAR),a satellite-based remote sensing technique,has application for monitoring subsidence with high resolution over short periods.DInSAR uses radar images to measure centimeter-level surface displacements.In the images,ground resolution can be relatively high,with each data point(pixel)representing the average displacement over an area of several square meters.The image data are acquired regularly which allows subsidence to be monitored sequentially over short periods;imaging periods typically range from weeks to months.Monitoring subsidence over short periods with high spatial resolution has potential to provide insight into the dynamics of subsidence and into relationships between mine advance and subsidence.In this study,for three longwall mines in the western United States,initial subsidence occurring at the start of longwall advance is quantified over short periods(12–72 days).C-band interferometric wide swath Synthetic Aperture Radar(SAR)images from the Sentinel satellites are used to quantify the subsidence.Overall,the data show initial development of subsidence,expansion of the subsidence trough,and the advance of subsidence in the direction of mining.
基金provided by the National Institute for Occupational Safety and Health,NIOSH(No.211-2014-60050)
文摘Most, if not all longwall gob areas accumulate explosive methane-air mixtures that pose a deadly hazard to miners. Numerous mine explosions have originated from explosive gas zones(EGZs) in the longwall gob. Since 2010, researchers at the Colorado School of Mines(CSM) have studied EGZ formation in longwall gobs under two long-term research projects funded by the National Institute for Occupational Safety and Health. Researchers used computational fluid dynamics along with in-mine measurements. For the first time, they demonstrated that EGZs form along the fringe areas between the methane-rich atmospheres and the fresh air ventilated areas along the working face and present an explosion and fire hazard to mine workers. In this study, researchers found that, for progressively sealed gobs, a targeted injection of nitrogen from the headgate and tailgate, along with a back return ventilation arrangement, will create a dynamic seal of nitrogen that effectively separates the methane zone from the face air and eliminates the EGZs to prevent explosions. Using this form of nitrogen injection to create dynamic seals should be a consideration for all longwall operators.
文摘This paper presents the results of numerical simulations carried out to confirm the influence of former mining activities on deformation of the mining terrain.The assessment of deformation changes was carried out with the use of FLAC3 D program based on the finite difference method.Numerical calculations were carried out for the example of actual mining operations in seams 703/1-2 and 707/2 of‘‘Marcel"Coal Mine.Taking into account the influence of the model’s plastic features and the so-called activation of a higher occurring seam in conducted simulations enabled obtaining a very good description of the measured subsidence.Based on the results one may state that numerical model can be used to assess the influence of former mining activities and the direction of conducted exploitation on deformations of the mining terrain.These factors are not recognized by geometric-integral theories commonly used for predicting the influence of mining operations on the surface.The results presented in this paper confirm that the applied method of simulating the phenomenon of reactivation of post-mining goafs is correct.
基金the fund supported by the National Natural Science Foundation of China(Grant No.U1261207)
文摘The paper presents the influence of varying immediate roof thickness on the lower strong roof strata movement and failure pattern in longwall coal mining with large mining height. The investigation is based on 58 geological drill holes and hydraulic shield pressure measurements around the longwall Panel 42105 of the Buertai Mine in Inner Mongolia Autonomous Region, China. The longwall Panel 42105 is characterized by relatively soft immediate roof strata of varying thickness superposed by strong strata,herein defined as lower strong roof. A voussoir beam model is adopted to interpret the structural movement of the lower strong roof strata and shield pressure measurements. It is shown that when the immediate roof is relatively thick, the broken overlying lower strong roof tends to form a stable voussoir beam with previously broken layer, thus not exerting high pressure on the hydraulic shield and working face. When the immediate roof is relatively thin, the broken overlying lower strong roof tends to behave as a cantilever beam, thus exerting higher pressure on the hydraulic shield and working face. Comparison of model predictions with measured time-weighted average shield pressure(TWAP) shows good agreement.
文摘Wellbore instability is reported frequently as one of the most significant incidents during drilling operations.Analysis of wellbore instability includes estimation of formation mechanical properties and the state of in situ stresses.In this analysis,the only controllable parameter during drilling operation is the mud weight.If the mud weight is larger than anticipated,the mud will invade into the formation,causing tensile failure of the formation.On the other hand,a lower mud weight can result in shear failures of rock,which is known as borehole breakouts.To predict the potential for failures around the wellbore during drilling,one should use a failure criterion to compare the rock strength against induced tangential stresses around the wellbore at a given mud pressure.The Mohr–Coulomb failure criterion is one of the commonly accepted criteria for estimation of rock strength at a given state of stress.However,the use of other criteria has been debated in the literature.In this paper,Mohr–Coulomb,Hoek–Brown and Mogi–Coulomb failure criteria were used to estimate the potential rock failure around a wellbore located in an onshorefield of Iran.The log based analysis was used to estimate rock mechanical properties of formations and state of stresses.The results indicated that amongst different failure criteria,the Mohr–Coulomb criterion underestimates the highest mud pressure required to avoid breakouts around the wellbore.It also predicts a lower fracture gradient pressure.In addition,it was found that the results obtained from Mogi–Coulomb criterion yield a better comparison with breakouts observed from the caliper logs than that of Hoek–Brown criterion.It was concluded that the Mogi–Coulomb criterion is a better failure criterion as it considers the effect of the intermediate principal stress component in the failure analysis.
文摘The purpose of this research was to develop a new approach in determination of overhaul and maintenance cost of loading equipment in surface mining. Two statistical models including univariate exponential regression (UER) and multivariate linear regression (MLR) were used in this study. Loading equipment parameters such as bucket capacity, machine weight, engine power, boom length, digging depth, and dumping height were considered as variables. The results obtained by models and mean absolute error rate indicate that these models can be applied as the useful tool in determination of overhaul and maintenance cost of loading equipment. The results of this study can be used by the decision-makers for the specific surface mining operations.
基金funded by the United Foundation key project fund,Chinese Natural Science Committee (No.U1261207)Datong Coal Group,Tashan Coal Mine,and supported by the Natural Science Foundation of Ningbo of China (No.U1261207)
文摘Coal seams in Tashan Mine of Datong Coal Group in China average 15 m thick and have been mined by the top coal caving longwall mining method of large mining height. Mining height was 3.8 m and the top coal caving height was 11.2 m. The gateroad pillar between panels was 38 m. During retreat mining,serious bumps occurred in the gateroads on both sides of the pillar affecting safety production. Therefore,pillarless mining was experimented. Using numerical modeling and comparative study of cases of similar mining condition,it was decided to employ a 6 m wide pillar,rather than the previous 38 m wide pillar.Support system for the gateroads was designed and implemented. During gateroad development,pillar failure conditions and entry deformation were monitored. Hydraulic fracturing method was employed to cut off the K3 sandstone along the entry rib so as to reduce the abutment pressure induced during retreat mining. Support reinforcement method combining grouting and advanced reinforcement methods was proposed to insure stable gateroad ahead of mining. Methane drainage and nitrogen injection were implemented to eliminate hazards associated with mine fire and spontaneous combustion. Since the development of gateroad has just completed,and retreat mining has not begun,the effectiveness of the proposed methods is unknown at this point. However,monitoring will continue until after mining.The results will be published in a separate paper.
基金sponsored by the Alpha Foundation for the Improvement of Mine Safety and Health, Inc
文摘‘‘Web ground control"(web GC) provides users with instantaneous access to mine design applications anywhere, at any time, through a web browser.Utilizing a web-based multiple-tier architecture, users are able to easily access ground control designs, perform on-demand calculations in the field, as well as facilitate project collaborations across multiple users, devices, and operating systems.Currently, the web GC platform contains five ground control related design applications previously developed and distributed by the US National Institute of Occupational Safety and Health(NIOSH), that is, analysis of roof bolt stability(ARBS), analysis of longwall pillar stability(ALPS), analysis of retreat mining stability(ARMPS), analysis of retreat mining stability–highwall mining(ARMPS-HWM), and analysis of horizontal stress in mining(AHSM).With respect to design decisions made by the web GC development team, the web GC platform will be able to further integrate future mine design applications providing the mining industry with one of a kind umbrella suite of ground control related software available at ones fingertips.The following paper provides a detailed overview on the current state of the web GC platform with discussions ranging from back-end database development and design to the front-end user-platform interface.Based on current progress in platform development as well as beta testing results, the web GC platform is scheduled for release in the fall of 2018.
文摘Directive(EU)2017/164 establishes a fourth list of indicative occupational exposure limit values(IOELVs)to protect workers from risks of exposure to hazardous chemicals.It states that in underground mining and tunnelling,Member States may benefit from a transitional period regarding IOELVs for nitrogen monoxide,nitrogen dioxide,and carbon monoxide,during which the existing established IOELVs may be applied.The European Advisory Committee on Health and Safety at Work questions the technical feasibility of the proposed IOELVs in underground mining(CO,NO and NO2)and tunnelling(NO and NO2).Challenges arise concerning the availability of measurement methodologies for compliance with proposed IOELVs(NO2)in underground mining and tunnelling environments.
