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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 *** 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 *** are various methods that can be used to approximate mining-induced loads in stratified rock masses to be used in pillar *** empirical methods are based on equations derived from large databases of various case *** are implemented in government approved design tools and are widely *** are also analytical and numerical techniques used for more detailed analysis of the induced *** this study,two different longwall mines with different panel width-to-depth ratios are analyzed using different *** 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 *** 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 *** 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 *** 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 *** FLAC3D model was observed to better capture the stress changes observed during the field measurements for both

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

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

Geotechnical considerations for concurrent pillar recovery in close-distance multiple seams

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International Journal of Mining Science and Technology 2018年第1期28卷 21-27页

作者： Peter Zhang berk tulu Morgan Sears Jack Trackemas Ground Control Branch NIOSHPittsburgh Mining Research Division Department of Mining Engineering West Virginia University

Room-and-pillar mining with pillar recovery has historically been associated with more than 25% of all ground fall fatalities in underground coal mines in the United *** risk of ground falls during pillar recovery increases in multiple-seam mining *** hazards associated with pillar recovery in multiple-seam mining include roof cutters, roof falls, rib rolls, coal outbursts, and floor *** pillar recovery is planned in multiple seams, it is critical to properly design the mining sequence and panel layout to minimize potential seam *** paper addresses geotechnical considerations for concurrent pillar recovery in two coal seams with 21 m of interburden under about 305 m of depth of *** study finds that, for interburden thickness of 21 m, the multiple-seam mining influence zone in the lower seam is directly under the barrier pillar within about 30 m from the gob edge of the upper *** peak stress in the interburden transfers down at an angle of approximately 20°away from the gob, and the entries and crosscuts in the influence zone are subjected to elevated stress during development and *** study also suggests that, for full pillar recovery in close-distance multiple-seam scenarios,it is optimal to superimpose the gobs in both seams, but it is not necessary to superimpose the *** the entries and/or crosscuts in the lower seam are developed outside the gob line of the upper seam,additional roof and rib support needs to be considered to account for the elevated stress in the multiple-seam influence zone.

关键词： Pillar recovery Room-and-pillar Retreat mining Multiple seam Mining sequence Pillar design

Influence of longwall mining on the stability of gas wells in chain pillars

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International Journal of Mining Science and Technology 2020年第1期30卷 3-9页

作者： Peter Zhang Heather Dougherty Daniel Su Jack Trackemas berk tulu CDC NIOSH Pittsburgh Mining Research Division(PMRD)PittsburghPA 15236USA Department of Mining Engineering West Virginia UniversityMorgantownWV 26505USA

Longwall mining has a significant influence on gas wells located within longwall chain *** subsidence and abutment pressure induced by longwall mining can cause excessive stresses and deformations in gas well *** the gas well casings are compromised or ruptured,natural gas could migrate into the mine workings,potentially causing a fire or *** the current safety regulations,the gas wells in the chain pillars have to be either plugged or protected by adequate coal *** current regulations for gas well pillar design are based on the 1957 Pennsylvania gas well pillar *** 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 *** the guidelines were developed for room-andpillar mining under shallow cover,they are no longer applicable to modern longwall coal mining,particularly,under deep *** well casing of failures have occurred even though the chain pillars for the gas wells met the requirements by the 1957 *** 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 *** study results indicate that overburden depth and pillar size are not the only determining factors for gas well *** other important factors include subsurface ground movement,overburden geology,weak floor,as well as the type of the construction of gas *** modeling was used to model abutment pressure,subsurface deformations,and the response of gas well *** 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 l

关键词： Longwall mining Gas well Chain pillar Casing stability

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

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

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 *** 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

Assessing support alternatives for longwall gateroads subject to changing stress

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International Journal of Mining Science and Technology 2021年第1期31卷 103-110页

作者： Gabriel S.Esterhuizen I.berk tulu Dave F.Gearhart Heather Dougherty Mark Van Dyke National Institute for Occupational Safety and Health Pittsburgh Mining Research DivisionPittsburghPA 15236USA West Virginia University MorgantownWV 26506USA

Longwall gateroad entries are subject to changing horizontal and vertical stress induced by redistribution of loads around the extracted *** stress changes can result in significant deformation of the entries that may include roof sag,rib dilation,and floor *** operators install different types of supports to control the ground response and maintain safe access and ventilation of the longwall *** paper describes recent research aimed at quantifying the effect of longwall-induced stress changes on ground stability and using the information to assess support *** research included monitoring of ground and support interaction at several operating longwall mines in the U.S.,analysis and calibration of numerical models that adequately represent the bedded rock mass,and observation of the support systems and their response to changes in *** models were then used to investigate the impact of geology and stress conditions on ground deformation and support response for various depths of cover and geologic *** research results were summarized in two regression equations that can be used to estimate the likely roof deformation and height of roof yield due to longwall-induced stress *** information is then used to assess the ability of support systems to maintain the stability of the *** application of the method is demonstrated with a retrospective analysis of the support performance at an operating longwall mine that experienced a headgate roof *** method is shown to produce realistic estimates of gateroad entry stability and support performance,allowing alternative support systems to be assessed during the design and planning stage of longwall operations.

关键词： Longwall Gateroad Support design Coal Standing support

A case study of multi-seam coal mine entry stability analysis with strength reduction method

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International Journal of Mining Science and Technology 2016年第2期26卷 193-198页

作者： tulu Ihsan berk Esterhuizen Gabriel S. Klemetti Ted Murphy Michael M. Sumner James Sloan Michael Ground Control Branch NIOSH Office of Mine Safety and Health Research Pittsburgh PA 15216 USA Lone Mountain Processing Inc. St. Charles VA 24282 USA

In this paper,the advantage of using numerical models with the strength reduction method(SRM) to evaluate entry stability in complex multiple-seam conditions is demonstrated.A coal mine under variable topography from the Central Appalachian region is used as a case *** this mine,unexpected roof conditions were encountered during development below previously mined *** mapping and observation of ground conditions were used to quantify the success of entry support systems in three room-and-pillar *** model analyses were initially conducted to estimate the stresses induced by the multiple-seam mining at the locations of the affected *** SRM was used to quantify the stability factor of the supported roof of the entries at selected *** SRM-calculated stability factors were compared with observations made during the site visits,and the results demonstrate that the SRM adequately identifies the unexpected roof conditions in this complex *** is concluded that the SRM can be used to effectively evaluate the likely success of roof supports and the stability condition of entries in coal mines.

关键词： Coal mine ground control Multiple seam mining Phase 2 FLAC3D Strength reduction method Roof supports