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

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 *** 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 *** primary focus was on the extent and magnitude of the abutment loading experienced by the standing *** 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 *** Flac3D program was used to evaluate these four bleeder entries using previously defined modeling and input parameter estimation *** results indicated only a minor increase in load during the extraction of the longwall *** 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 *** Flac3D model showed very good correlation between expected gateroad loading during panel extraction and that expected based on previous *** results of this study showed that the rear abutment stress experienced by this bleeder entry design was *** farther away from the startup room, the lower the applied load and smaller the convergence in the entry if all else is held ***, the numerical modeling method

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

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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 *** anticipate and mitigate adverse geologic conditions,a formal method to evaluate geotechnical factors must be *** mine is unique and has its own separate approach for defining what an adverse geological condition consists *** collection of geologic data is a first critical step to creating a geological database to map these hazards efficiently and *** 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 *** 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 *** information,delivered in a timely manner,allows mining personnel to be proactive in mine planning and support implementations,ultimately reducing the impacts of these *** paper covers geologic exploratory methods,data organization,and the value of collecting and interpreting geologic information in coal mines to enhance safety and *** implementation of the methods described above has been proven effective in predicting and mitigating adverse geologic conditions in underground coal *** 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 *** 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 *** refinements and standardization of data collection methods,

关键词： Roof control Database Mapping Hazards Geology

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Coal mine entry rating system:A case study

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International Journal of Mining Science and Technology 2021年第1期31卷 145-151页

作者： mark A.van dyke Ted M.Klemetti Craig Compton National Institute for Occupational Safety and Health Pittsburgh Mining Research DivisionPittsburghPA 15236USA

Coal mines are continuously seeking to determine the performance of entries with different ground control products and installation *** are many factors that impact how an entry will perform which include but are not limited to geology,overburden,bolting type and pattern,and mine *** the National Institute for Occupational Safety and Health(NIOSH),research has been instituted to examine the relationship of the parts of a coal mine entry as a system and not as individual *** study this relationship,the first step in this study was to create a numeric rating system that accurately reflects visual observations of the mine entry and is easy to *** researchers devised this rating system to improve upon previous ideas,offering increased flexibility which can be incorporated into an overall entry condition that offers different levels of confidence based on the user’s time devoted to the *** new entry rating system was implemented at three different mines over varying periods of time to evaluate the ground response to the geology,bolt installation pattern,stress changes by mining,overburden,and time dependency.

关键词： Coal Geology Rating system Support

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Preliminary rib support requirements for solid coal ribs using a coal pillar rib rating(CPRR)

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International Journal of Mining Science and Technology 2021年第1期31卷 15-22页

作者： Khaled Mohamed mark van dyke Gamal Rashed Morgan MSears Robert Kimutis National Institute for Occupational Safety and Health Pittsburgh Mining Research DivisionPittsburghPA 15236USA

Researchers from the National Institute for Occupational Safety and Health(NIOSH)are developing a coal pillar rib rating(CPRR)technique to measure the integrity of coal *** CPRR characterizes the rib composition and evaluates its impact on the inherent stability of the coal *** CPRR utilizes four parameters:rib homogeneity,bedding condition,face cleat orientation with respect to entry direction,and rib *** these parameters are measurable in the field.A rib data collecting procedure and a simple sheet to calculate the CPRR were *** developed CPRR can be used as a rib quality mapping tool in underground coal mines and to determine the potential of local rib instabilities and support requirements associated with overburden *** calculations were conducted for 22 surveyed solid coal ribs,mainly composed of coal *** on this study,the rib performance was classified into four categories.A preliminary minimum primary rib support density(PRSD)line was obtained from these surveyed *** sample cases are presented that illustrate the data collection form and CPRR calculations.

关键词： Coal rib stability Rib support design Coal pillar rib rating Rib quality mapping CPRR Coal classification

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Evaluation of seismic potential in a longwall mine with massive sandstone roof under deep overburden

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International Journal of Mining Science and Technology 2018年第1期28卷 115-119页

作者： mark A.van dyke Wen H.Su Joe Wickline Ground Control Branch NIOSHPittsburgh15236 PAUSA Coronado Coal LLC BeckleyWVUSA

A recent seismic event was recorded by a deep longwall mine in Virginia at 3.7 ML on the local magnitude scale and 3.4 MMS by the United States Geological Survey(USGS) in *** investigations by the National Institute for Occupational Safety and Health(NIOSH) and Coronado Coal researchers have shown that this event was associated with geological features that have also been associated with other, similar seismic events in *** mapping and geological exploration in the mining area has made it possible to forecast possible locations for future seismic *** order to use the geology as a forecaster of mining-induced seismic events and their energy potential, two primary components are *** first component is a long history of recorded seismic events with accurately plotted *** second component is a high density of geologic data within the mining *** this case, 181 events of 1.0 MLor greater were recorded by the mine's seismic network between January, 2009, and October, *** the mining area, 897 geophysical logs, 224 core holes, and 1031 fiberscope holes were examined by mine *** this information, it was found that overburden thickness, sandstone thickness, and sandstone quality contributed greatly to seismic *** the data was analyzed, a pattern became apparent indicating that the majority of seismic events occurred under specific *** forecast maps were created based on geology of previous seismic *** forecast maps have shown an accuracy of within 74%–89% when compared to the recorded 181 events that were1.0 MLor greater when considering three major geological criteria of overburden thickness of 579.12 m or greater, 6.096–12.192 m of sandstone within 15.24 m of the Pocahontas number 3 seam, and a longwall caving height of 4.572 m or less.

关键词： Seismic Mapping Deep overburden Massive sandstone

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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 ***,applying a quantitative methodology to describe floor quality with a single number provides a practical estimate for preliminary assessment of floor *** 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 *** most significant components of the CMFR are uniaxial compressive strength and discontinuity intensity of floor *** addition to the competence of the floor,depth of cover and stress notch angle are input parameters used to assess the preliminary floor *** this study,CMFR methodology was applied to a Central Appalachian Coal Mine that intermittently experienced floor *** drill core data,overburden maps,and mine plans were utilized for the ***,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 *** was found that the current CMFR classification system is not directly applicable in assessing the floor stability of the Central Appalachian Coal *** 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

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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 *** 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 *** paper is focused on the stability of the longwall entries subjected to a single abutment load such as bleeders,first tailgate,and last *** 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 *** modeling was also conducted to evaluate various support types with further investigation and comparison to the condition *** 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

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Effect of longwall-induced subsurface deformations on shale gas well casing stability under deep covers

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International Journal of Mining Science and Technology 2019年第1期29卷 3-8页

作者： Daniel W.H.Su Peter Zhang mark van dyke Todd Minoski Center for Disease Control and Prevention(CDC) National Institute for Occupational Safety and Health(NIOSH)Pittsburgh Mining Research Division(PMRD)

This paper presents the results of a 2017 study conducted by the National Institute for Occupational Safety and Health(NIOSH), Pittsburgh Mining Research Division(PMRD), to evaluate the effects of longwall-induced subsurface deformations within a longwall abutment pillar under deep cover. The 2017 study was conducted in a southwestern Pennsylvania coal mine, which extracts 457 m-wide longwall panels under 361 m of cover. One 198 m-deep, in-place inclinometer monitoring well was drilled and installed over a 45 m by 84 m center abutment pillar. In addition to the monitoring well, surface subsidence measurements and underground coal pillar pressure measurements were conducted as the 457 m-wide longwall panel on the south side of the abutment pillar was being mined. Prior to the first longwall excavation, a number of simulations using FLAC3D^(TM) were conducted to estimate surface subsidence, increases in underground coal pillar pressure, and subsurface horizontal displacements in the monitoring well. Comparisons of the pre-mining FLAC3D simulation results and the surface, subsurface,and underground instrumentation results show that the measured in-place inclinometer casing deformations are in reasonable agreement with those predicted by the 3D finite difference models. The measured surface subsidence and pillar pressure are in excellent agreement with those predicted by the 3D *** from this 2017 research clearly indicate that, under deep cover, the measured horizontal displacements within the abutment pillar are approximately one order of magnitude smaller than those measured in a 2014 study under medium cover.

关键词： Longwall Deformations Shale gas wells Casing Safety and health

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Ground response to high horizontal stresses during longwall retreat and its implications for longwall headgate support

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International Journal of Mining Science and Technology 2019年第1期29卷 27-33页

作者： Peter Zhang Dave Gearhart mark van dyke Daniel Su Essie Esterhuizen Berk Tulu NIOSH Pittsburgh Mining Research Division(PMRD) Department of Mining Engineering West Virginia University

Roof falls in longwall headgate can occur when weak roof and high horizontal stress are present. To prevent roof falls in the headgate under high horizontal stress, it is important to understand the ground response to high horizontal stress in the longwall headgate and the requirements for supplemental roof support. In this study, a longwall headgate under high horizontal stress was instrumented to monitor stress change in the pillars, deformations in the roof, and load in the cable bolts. The conditions in the headgate were monitored for about six months as the longwall face passed by the instrumented *** roof behavior in the headgate near the face was carefully observed during longwall *** modeling was performed to correlate the modeling results with underground observation and instrumentation data and to quantify the effect of high horizontal stress on roof stability in the longwall headgate. This paper discusses roof support requirements in the longwall headgate under high horizontal stress in regard to the pattern of supplemental cable bolts and the critical locations where additional supplemental support is necessary.

关键词： Longwall mining Longwall headgate High horizontal stress Supplemental support

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Analysis of gateroad stability at two longwall mines based on field monitoring results and numerical model analysis

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International Journal of Mining Science and Technology 2019年第1期29卷 35-43页

作者： Gabriel S.Esterhuizen David F.Gearhart Ted Klemetti Heather Dougherty mark van dyke National Institute for Occupational Safety and Health

Coal mine longwall gateroads are subject to changing loading conditions induced by the advancing longwall face. The ground response and support requirements are closely related to the magnitude and orientation of the stress changes, as well as the local geology. This paper presents the monitoring results of gateroad response and support performance at two longwall mines at a 180-m and 600-m depth of *** the first mine, a three-entry gateroad layout was used. The second mine used a four-entry, yieldabutment-yield gateroad pillar system. Local ground deformation and support response were monitored at both sites. The monitoring period started during the development stage and continued during first panel retreat and up to second panel retreat. The two data sets were used to compare the response of the entries in two very different geotechnical settings and different gateroad layouts. The monitoring results were used to validate numerical models that simulate the loading conditions and entry response for these widely differing conditions. The validated models were used to compare the load path and ground response at the two mines. This paper demonstrates the potential for numerical models to assist mine engineers in optimizing longwall layouts and gateroad support systems.

关键词： Coal mining Longwall Gateroad Support Numerical models

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