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| 1 | Analysis of the current rib support practices and techniques in U.S. coal mines显示文摘Design of rib support systems in U.S. coal mines is based primarily on local practices and experience. A better understanding of current rib support practices in U.S. coal mines is crucial for developing a sound engineering rib support design tool. The objective of this paper is to analyze the current practices of rib control in U.S. coal mines. Twenty underground coal mines were studied representing various coal basins,coal seams,geology,loading conditions,and rib control strategies. The key findings are:(1) any rib design guideline or tool should take into account external rib support as well as internal bolting;(2) rib bolts on their own cannot contain rib spall,especially in soft ribs subjected to significant load—external rib control devices such as mesh are required in such cases to contain rib sloughing;(3) the majority of the studied mines follow the overburden depth and entry height thresholds recommended by the Program Information Bulletin 11-29 issued by the Mine Safety and Health Administration;(4) potential rib instability occurred when certain geological features prevailed—these include draw slate and/or bone coal near the rib/roof line,claystone partings,and soft coal bench overlain by rock strata;(5) 47% of the studied rib spall was classified as blocky—this could indicate a high potential of rib hazards; and(6) rib injury rates of the studied mines for the last three years emphasize the need for more rib control management for mines operating at overburden depths between 152.4 m and 304.8 m. | Mohamed Khaled M. Murphy Michael M. Lawson Heather E. Klemetti Ted | 2016 | International Journal of Mining Science and Technology2016，26，1： | 6 |
| 2 | A case study of multi-seam coal mine entry stability analysis with strength reduction method显示文摘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 study.At this mine,unexpected roof conditions were encountered during development below previously mined panels.Stress mapping and observation of ground conditions were used to quantify the success of entry support systems in three room-and-pillar panels.Numerical model analyses were initially conducted to estimate the stresses induced by the multiple-seam mining at the locations of the affected entries.The SRM was used to quantify the stability factor of the supported roof of the entries at selected locations.The 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 case.It 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. | Tulu Ihsan Berk Esterhuizen Gabriel S. Klemetti Ted Murphy Michael M. Sumner James Sloan Michael | 2016 | International Journal of Mining Science and Technology2016，26，2： | 5 |
| 3 | Analysis of gateroad stability at two longwall mines based on field monitoring results and numerical model analysis显示文摘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 cover.At 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. | Gabriel S.Esterhuizen David F.Gearhart Ted Klemetti Heather Dougherty Mark van Dyke | 2019 | International Journal of Mining Science and Technology2019，29，1： | 5 |
| 4 | Design concerns of room and pillar retreat panels显示文摘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 geologic changes in the immediate roof. The second is that in order to successfully retreat an R &P panel, a three-phased approach to the design and analysis of the panel should be conducted: the planning phase, evaluation phase, and monitoring phase. | Klemetti Ted M. Sears Morgan M. Tulu Ihsan B. | 2017 | International Journal of Mining Science and Technology2017，27，1： | 4 |
| 5 | Investigating different methods used for approximating pillar loads in longwall coal mines显示文摘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 allowed us to see the shortcomings of each of these different methods.It was concluded that a numerical model which incorporates the site-specific geology would provide the most precise estimate for complex loading conditions. | Deniz Tuncay a Ihsan Berk Tulu a Ted Klemetti | 2021 | International Journal of Mining Science and Technology2021，31，1： | 2 |
| 6 | Trabecular bone mineral density of mandible and alveolar height in postmenopausal women 显示文摘 | Klemetti E Vainio P Lassila V | 1993 | Scand J Dent Res1993，101，3： | 2 |
| 7 | Prevention of gesta- tional diabetes through lifestyle intervention:study design and methods of a finnish randomized controUed multicenter trial (RADIEL) 显示文摘 | RSnfi K Stach - Lempinen B Klemetti MM et aI | 2014 | BMC Pregnancy Childbirth2014，14，： | 1 |
| 8 | Maternal socio-economic indices for prenatal care research in rural China显示文摘 | Nwaru B I Klemetti R Kun H | 2012 | The European Journal of Public Health2012，22，6： | 1 |
| 9 | Shade selection performed by novice dental professionals and colorimeter显示文摘 | Klemetti E Matela AM Haag P | 2006 | J Oral Rehabil2006，33，1： | 1 |
| 10 | Cancer morbidity in a cohort of 9175 Finnish women treated for infertility 显示文摘 | Yli-Kuha AN Gissler M Klemetti R | 2012 | Hum Reprod2012，27，： | 1 |
| 11 | Pantomography in assessment of the osteoporosis risk group显示文摘 | Klemetti E Kolmakov S Kroger H | 1994 | Scand J Dent Res1994，102，1： | 1 |
| 12 | Cesarean section delivery among primiparous women in rural China: an emerging epidemic 显示文摘 | Klemetti R Che X Gao Y | 2010 | Am J Obstet Gynecol2010，202，65： | 1 |
| 13 | Cesarean section delivery among primiparous women in rural China:an emerging epidemic 显示文摘 | Klemetti R Che X Gao Y | 2010 | Am J Obstet Gyneco12010，202，65： | 1 |
| 14 | IL-23/IL-17 immunity as a hallmark of Crohn' s disease 显示文摘 | Hota V Klemetti P Sipponen T | 2008 | Inflamm Bowel Dis2008，14，9： | 1 |
| 15 | Health of children born as a result of in vitro fertilization显示文摘 | Klemetti R Sevón T Gissler M | 2006 | Pediatrics2006，118，5： | 1 |
| 16 | Geologic data collection and assessment techniques in coal mining for ground control显示文摘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 improvement in technology,the evaluation of adverse geologic conditions will evolve and continue to improve the safety and productivity of underground coal mining. | Mark Van Dyke Ted Klemetti Joe Wickline | 2020 | International Journal of Mining Science and Technology2020，30，1： | 1 |
| 17 | Birth outcomes after induced abortion:a nationwide register-based study of first births in Finland显示文摘 | Klemetti R Gissler M Niinimaki M | 2012 | Hum Reprod2012，27，11： | 1 |
| 18 | Trabecular bone mineral density of mandible and alveolar height in postmenopausal women显示文摘 | Vainio P Lassila V | 1993 | Scand J dent Res1993，101，3： | 1 |
| 19 | Mic- rosatellite polymorphism in the heme oxygenase-1 pro- moter is associated with nonsevere and late-onsetpre- eclampsia显示文摘 | Kaartokallio T Klemetti M M Timonen A | 2014 | Hypertension2014，64，1： | 1 |
| 20 | Cesarean section delivery a-mong primiparous women in rural China:an emerging epidemic显示文摘 | Klemetti R Che X GaoY | 2009 | Am J Obstet Gynecol2009，216，7： | 1 |
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