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Deep cover bleeder entry performance and support loading: A case study

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International Journal of mining Science and Technology 2018年第1期28卷 85-93页

作者： Ted M.Klemetti mark Alexander Van Dyke Ihsan Berk Tulu Ground Control Branch NIOSHPittsburgh Mining Research Division mining Engineering Department West Virginia University

Several questions have emerged in relation to deep cover bleeder entry performance and support loading:how well do current modeling procedures calculate the rear abutment extent and loading? Does an improved understanding of the rear abutment extent warrant a change in standing support in bleeder entries? To help answer these questions and to determine the current utilization of standing support in bleeder entries, four bleeder entries at varying distances from the startup room were instrumented,observed, and numerically modeled.This paper details observations made by NIOSH researchers in the bleeder entries of a deep cover longwall panel—specifically data collected from instrumented pumpable cribs, observations of the conditions of the entries, and numerical modeling of the bleeder entries during longwall extraction.The primary focus was on the extent and magnitude of the abutment loading experienced by the standing support.As expected, the instrumentation of the standing supports showed very little loading relative to the capacity of the standing supports—less than 23 mg load and 2.54 cm convergence.The Flac3D program was used to evaluate these four bleeder entries using previously defined modeling and input parameter estimation procedures.The results indicated only a minor increase in load during the extraction of the longwall panel.The model showed a much greater increase in stress due to the development of the gateroad and bleeder entries, with about 80% of the increase associated with development and 20% with longwall extraction.The Flac3D model showed very good correlation between expected gateroad loading during panel extraction and that expected based on previous studies.The results of this study showed that the rear abutment stress experienced by this bleeder entry design was minimal.The farther away from the startup room, the lower the applied load and smaller the convergence in the entry if all else is held constant.Finally, the numerical modeling method used in this study was capable of replicating t

关键词： Bleeder entry Standing supports Abutment loading Longwall mining Full extraction

Bleeder entry evaluation using condition mapping and numerical modeling

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International Journal of mining Science and Technology 2021年第1期31卷 137-143页

作者： Ted M.Klemetti mark A.Van Dyke Gabriel S.Esterhuizen National Institute for Occupational Safety and Health Pittsburgh Mining Research DivisionPittsburghPA 15236USA

One of the most common critical areas of longwall mining in terms of ground stability are the gateroad and bleeder entries.These critical entries provide much-needed safe access for miners and allow for adequate ventilation required for dilution of hazardous airborne contaminants and must remain open during mining of a multi-panel district.This paper is focused on the stability of the longwall entries subjected to a single abutment load such as bleeders,first tailgate,and last headgate.First tailgate and last headgate are also referred to as blind headgate and tailgate.A study of a longwall district through conditions mapping,support evaluations,and numerical modeling was conducted and evaluated by researchers from the National Institute for Occupational Safety and Health(NIOSH).The condition mapping and support evaluations were performed on entries that spanned the previous five years of mining and relied on a diverse selection of supports to maintain the functionality of the entry.Numerical modeling was also conducted to evaluate various support types with further investigation and comparison to the condition mapping.The study demonstrated the importance of the abutment load decay versus distance from the gob edge,the potential for a reduction in material handling related injuries,as well as optimal usage of secondary and standing support.

关键词： Stability assessment Bleeder entry Abutment loading Condition mapping Longwall Ground control

Geologic data collection and assessment techniques in coal mining for ground control

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International Journal of mining Science and Technology 2020年第1期30卷 131-139页

作者： mark Van Dyke ted klemetti Joe Wickline NIOSH Pittsburgh15236 PAUSA Coronado Global Resources Inc. BeckleyWVUSA

The identification and mitigation of adverse geologic conditions are critical to the safety and productivity of underground coal mining operations.To anticipate and mitigate adverse geologic conditions,a formal method to evaluate geotechnical factors must be established.Each mine is unique and has its own separate approach for defining what an adverse geological condition consists of.The collection of geologic data is a first critical step to creating a geological database to map these hazards efficiently and effectively.many considerations must be taken into account,such as lithology of immediate roof and floor strata,seam height,gas and oil wells,faults,depressions in the mine floor(water)and increases in floor elevation(gas),overburden,streams and horizontal stress directions,amongst many other factors.Once geologic data is collected,it can be refined and integrated into a database that can be used to develop maps showing the trend,orientation,and extent of the adverse geological conditions.This information,delivered in a timely manner,allows mining personnel to be proactive in mine planning and support implementations,ultimately reducing the impacts of these features.This paper covers geologic exploratory methods,data organization,and the value of collecting and interpreting geologic information in coal mines to enhance safety and production.The implementation of the methods described above has been proven effective in predicting and mitigating adverse geologic conditions in underground coal mining.Consistent re-evaluation of data collection methods,geologic interpretations,mapping procedures,and communication techniques ensures continuous improvement in the accuracy of predictions and mitigation of adverse geologic conditions.Providing a concise record of the work previously done to track geologic conditions at a mine will allow for the smoothest transition during employee turnover and transitions.With refinements and standardization of data collection methods,such as those described in this paper,along with

关键词： Roof control Database mapping Hazards Geology

Analysis of ARmPS2010 database with Lamodel and an updated abutment angle equation

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International Journal of mining Science and Technology 2020年第1期30卷 111-118页

作者： Deniz Tuncay Ihsan Berk Tulu ted klemetti Department of mining Engineering West Virginia UniversityMorgantownWV 26505USA National Institute for Occupational Safety and Health Pittsburgh Mining Research DivisionPittsburghPA 15236USA

The Analysis of Retreat mining Pillar Stability(ARmPS) program was developed by the National Institute for Occupational Safety and Health(NIOSH) to help the United States coal mining industry to design safe retreat room-and-pillar panels. ARmPS calculates the magnitude of the in-situ and mining-induced loads by using geometrical computations and empirical rules. In particular, the program uses the "abutment angle" concept in calculating the magnitude of the abutment load on pillars adjacent to a gob. In this paper, stress measurements from United States and Australian mines with different overburden geologies with varying hard rock percentages were back analyzed. The results of the analyses indicated that for depths less than 200 m, the ARmPS empirical derivation of a 21° abutment angle was supported by the case histories;however, at depths greater than 200 m, the abutment angle was found to be significantly less than 21°. In this paper, a new equation employing the panel width to overburden depth ratio is constructed for the calculation of accurate abutment angles for deeper mining cases. The new abutment angle equation was tested using both ARmPS2010 and La model for the entire case history database of ARmPS2010. The new abutment angle equation to estimate the magnitude of the mining-induced loads used together with the La model program was found to give good classification accuracies compared to ARmPS2010 for deep cover cases.

关键词： Abutment angle ARmPS2010 Lamodel ARmPS-LAm Coal mining Pillar stability

Investigating different methods used for approximating pillar loads in longwall coal mines

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International Journal of mining Science and Technology 2021年第1期31卷 23-32页

作者： Deniz Tuncay a Ihsan Berk Tulu a ted klemetti Department of mining Engineering West Virginia UniversityMorgantown 26501USA NIOSH Pittsburgh mining Research Division Pittsburgh 15236USA

Accurately estimating load distributions and ground responses around underground openings play a significant role in the safety of the operations in underground mines.Adequately designing pillars and other support measures relies highly on the accurate assessment of the loads that will be carried by them,as well as the load-bearing capacities of the supports.There are various methods that can be used to approximate mining-induced loads in stratified rock masses to be used in pillar design.The empirical methods are based on equations derived from large databases of various case studies.They are implemented in government approved design tools and are widely used.There are also analytical and numerical techniques used for more detailed analysis of the induced loads.In this study,two different longwall mines with different panel width-to-depth ratios are analyzed using different methods.The empirical method used in the analysis is the square-decay stress function that uses the abutment angle concept,implemented in pillar design software developed by the National Institute for Occupational Safety and Health(NIOSH).The first numerical method used in the analysis is a displacement-discontinuity(DD)variation of the boundary element method,Lamodel,which utilizes the laminated overburden model.The second numerical method used in the analysis is Fast Lagrangian Analysis of Continua(FLAC)with the numerical modeling approach recently developed at West Virginia University which is based on the approach developed by NIOSH.The model includes the 2D slice of a cross-section along the width of the panel with the chain pillar system that also includes the different stratigraphic layers of the overburden.All three methods gave similar results for the shallow mine,both in terms of load percentages and distribution where the variation was more obvious for the deep cover mine.The FLAC3D model was observed to better capture the stress changes observed during the field measurements for both the shallow and deep cover cases.This study all

关键词： Abutment loads Numerical modeling Lamodel FLAC3D Longwall coal mines

Design concerns of room and pillar retreat panels

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International Journal of mining Science and Technology 2017年第1期27卷 29-35页

作者： klemetti ted m. Sears morgan m. Tulu Ihsan B. mining Engineer Ground Control Branch NIOSH Office of Mine Safety and Health ResearchPittsburghPAUSA

Why do some room and pillar retreat panels encounter abnormal conditions? What factors deserve the most consideration during the planning and execution phases of mining and what can be done to mitigate those abnormal conditions when they are encountered? To help answer these questions, and to determine some of the relevant factors influencing the conditions of room and pillar(R & P) retreat mining entries, four consecutive R & P retreat panels were evaluated. This evaluation was intended to reinforce the influence of topographic changes, depth of cover, multiple-seam interactions, geological conditions, and mining geometry. This paper details observations were made in four consecutive R & P retreat panels and the data were collected from an instrumentation site during retreat mining. The primary focus was on the differences observed among the four panels and within the panels themselves. The instrumentation study was initially planned to evaluate the interactions between primary and secondary support, but produced rather interesting results relating to the loading encountered under the current mining conditions. In addition to the observation and instrumentation, numerical modeling was performed to evaluate the stress conditions. Both the La model 3.0 and Rocscience Phase 2 programs were used to evaluate these four panels. The results of both models indicated a drastic reduction in the vertical stresses experienced in these panels due to the full extraction mining in overlying seams when compared to the full overburden load. Both models showed a higher level of stress associated with the outside entries of the panels. These results agree quite well with the observations and instrumentation studies performed at the mine. These efforts provided two overarching conclusions concerning R & P retreat mine planning and execution. The first was that there are four areas that should not be overlooked during R & P retreat mining: topographic relief, multiple-seam stress relief, stress concentrations near the gob edge,and g

关键词：面板支柱设计仪器仪表相互作用开采条件地形变化地质条件

Application of the coal mine floor rating(CmFR)to assess the floor stability in a Central Appalachian Coal mine

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International Journal of mining Science and Technology 2021年第1期31卷 83-89页

作者： Sena Cicek Ihsan Berk Tulu mark Van Dyke ted klemetti Joe Wickline Department of mining Engineering West Virginia UniversityMorgantownWV 26505USA National Institute for Occupational Safety and Health Pittsburgh Mining Research DivisionPittsburghPA 15236USA Coronado Global Resources Inc. BeckleyWV 25801USA

Estimating the overall floor stability in a coal mine using deterministic methods which require complex engineering properties of floor strata is desirable,but generally it is impractical due to the difficulty of gathering essential input data.However,applying a quantitative methodology to describe floor quality with a single number provides a practical estimate for preliminary assessment of floor stability.The coal mine floor rating(CmFR)system,developed by the University of New South Wales(UNSW),is a rockmass classification system that provides an indicator for the competence of floor strata.The most significant components of the CmFR are uniaxial compressive strength and discontinuity intensity of floor strata.In addition to the competence of the floor,depth of cover and stress notch angle are input parameters used to assess the preliminary floor stability.In this study,CmFR methodology was applied to a Central Appalachian Coal mine that intermittently experienced floor heave.Exploratory drill core data,overburden maps,and mine plans were utilized for the study.Additionally,qualitative data(failure/non-failure)on floor conditions of the mine entries near the core holes was collected and analyzed so that the floor quality and its relation to entry stability could be estimated by statistical methods.It was found that the current CmFR classification system is not directly applicable in assessing the floor stability of the Central Appalachian Coal mine.In order to extend the applicability of the CmFR classification system,the methodology was modified.A calculation procedure of one of the CmFR classification system’s components,the horizontal stress rating(HSR),was changed and new parameters were added to the HSR.

关键词： Rock mass classification Coal mine floor rating(CmFR) Floor heave Floor failure Buckling failure mechanism

Guest editorial–special issue on ground control in mining in 2020

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International Journal of mining Science and Technology 2021年第1期31卷 1-2页

作者： michael m.murphy ted klemetti Heather Lawson Brijes mishra Kyle Perry CDC NIOSH PittsburghPA 15236USA CDC NIOSH SpokaneWA 99207USA Department of mining Engineering West Virginia UniversityMorgantown 26501USA Department of mining Engineering Missouri University of Science and TechnologyRollaMO 65409USA

Ground control is the science of studying and controlling the behavior of rock strata in response to mining operations.Ground-control-related research has seen significant advancements over the last 40 years,and these accomplishments are well documented in the proceedings of the annual International Conference on Ground Control in mining(ICGCm)[1].The ICGCm is a forum to promote closer communication among researchers,consultants,regulators,manufacturers,and mine operators to expedite solutions to ground control problems in mining[2–7].Fundamental research and advancements in ground control science define the central core of the conference mission.Providing information to mine operators is a priority,as the conference goal is to offer solutions-oriented information.In addition,the conference has included innovative technologies and ideas in miningrelated fields such as exploration,geology,and surface and underground mining in all commodities.many new ground control technologies and design standards adopted by the mining industry were first discussed at ICGCm.This conference is recognized as the leading international forum for introducing new ground-control-related research and products.

关键词： operators closer accomplishment

Guest editorial-special issue on ground control in mining in 2019

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International Journal of mining Science and Technology 2020年第1期30卷 1-2页

作者： michael m.murphy ted klemetti Heather Lawson Brijes mishra Kyle Perry Pittsburgh mining Research Division NIOSHPittsburghPA 15228USA Spokane mining Research Division NIOSHSpokaneWA 99207USA mining Engineering West Virginia UniversityMorgantownWV 26506USA mining&Nuclear Engineering Missouri S&TRollaMO 65409USA

Ground control is the science of studying and controlling the behavior of rock strata in response to mining operations.Ground-control-related research has seen significant advancements over the last 39 years,and these accomplishments are well documented in the proceedings of the annual International Conference on Ground Control in mining(ICGCm)[1].The ICGCm is a forum to promote closer communication among researchers,consultants,regulators,manufacturers,and mine operators to expedite solutions to ground control problems in mining[2–7].Fundamental research and advancements in ground control science define the central core of the conference mission.Providing information to mine operators is a priority,as the conference goal is to offer solutions-oriented information.In addition,the conference has included innovative technologies and ideas in miningrelated fields such as exploration,geology,and surface and underground mining in all commodities.many new ground control technologies and design standards adopted by the mining industry were first discussed at ICGCm.Therefore,this conference is recognized as the best international forum for introducing new groundcontrol-related research and products.

关键词： operators closer accomplishment