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Analysis of monitored ground support and rock mass response in a longwall tailgate entry

international Journal of Mining Science and Technology 2018年第1期28卷 43-51页

作者： G.S.Esterhuizen D.F.Gearhart i.b.tulu NiOSH Pittsburgh Mining Research Division PittsburghPA 15236USA West Virginia University MorgantownWV 26506USA

A comprehensive monitoring program was conducted to measure the rock mass displacements, support response, and stress changes at a longwall tailgate entry in West Virginia.Monitoring was initiated a few days after development of the gateroad entries and continued during passage of the longwall panels on both sides of the entry.Monitoring included overcore stress measurements of the initial stress within the rock mass, changes in cable bolt loading, standing support pressure, roof deformation, rib deformation,stress changes in the coal pillar, and changes in the full three-dimensional stress tensor within the rock mass at six locations around the monitoring site.During the passage of the first longwall, stress measurements in the rock and coal detected minor changes in loading while minor changes were detected in roof deformation.As a result of the relatively favorable stress and geological conditions, the support systems did not experience severe loading or rock deformation until the second panel approached within 10–15 m of the instrumented locations.After reaching the peak loading at about 50–75 mm of roof sag, the cable bolts started to unload, and load was transferred to the standing supports.The standing support system was able to maintain an adequate opening inby the shields to provide ventilation to the first crosscut inby the face, as designed.The results were used to calibrate modeled cable bolt response to field data, and to validate numerical modeling procedures that have been developed to evaluate entry support systems.it is concluded that the support system was more than adequate to control the roof of the tailgate up to the longwall face location.The monitoring results have provided valuable data for the development and validation of support design strategies for longwall tailgate entries.

关键词： Longwall mining Support Tailgate Monitoring Coal mining

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A case study of the stability of a non-typical bleeder entry system at a U.S.longwall mine

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international Journal of Mining Science and Technology 2020年第1期30卷 25-31页

作者： T.M.Klemetti M.A.Van Dyke i.b.tulu D.Tuncay NiOSH Pittsburgh Mining Research Division Pittsburgh 15236USA Department of Mining Engineering West Virginia UniversityMorgantown 26505USA

Longwall abutment loads are influenced by several factors,including depth of cover,pillar sizes,panel dimensions,geological setting,mining height,proximity to gob,intersection type,and size of the gob.How does proximity to the gob affect pillar loading and entry condition?Does the gob influence depend on whether the abutment load is a forward,side,or rear loading?Do non-typical bleeder entry systems follow the traditional front and side abutment loading and extent concepts?if not,will an improved understanding of the combined abutment extent warrant a change in pillar design or standing support in bleeder entries?This paper details observations made in the non-typical bleeder entries of a moderate depth longwall panel—specifically,data collected from borehole pressure cells and roof extensometers,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 due to the extraction of the longwall panels.Due to the layout of the longwall panels and bleeder entries,the borehole pressure cells(bPCs)and roof extensometers did not show much change due to the advancing of the first longwall.However,they did show a noticeable increase due to the second longwall advancement,with a maximum of about 4 MPa of pressure increase and 5mmof roof deformation.The observations of the conditions showed little to no change from before the first longwall panel extraction began to when the second longwall panel had been advanced more than 915 m.Localized pillar spalling was observed on the corners of the pillars closest to the longwall gob as well as an increase in water in the entries.in addition to the observations and instrumentation,numerical modeling was performed to validate modeling procedures against the monitoring results and evaluate the bleeder design.iTASCA Consulting Group’s FLAC3D numerical modeling software was used to evaluate the bleeder entries.The results of the models indicate

关键词： Abutment loading Longwall instrumentation bore hole pressure cells Pillar loading Yield pillar bleeder pillar

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Analysis of global and local stress changes in a longwall gateroad

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international Journal of Mining Science and Technology 2018年第1期28卷 127-135页

作者： i.b.tulu G.S.Esterhuizen D.Gearhart T.M.Klemetti K.M.Mohamed D.W.H.Su Department of Mining Engineering West Virginia University NiOSH Pittsburgh Mining Research Division

A numerical-model-based approach was recently developed for estimating the changes in both the horizontal and vertical loading conditions induced by an approaching longwall face.in this approach, a systematic procedure is used to estimate the model's inputs.Shearing along the bedding planes is modeled with ubiquitous joint elements and interface elements.Coal is modeled with a newly developed coal mass model.The response of the gob is calibrated with back analysis of subsidence data and the results of previously published laboratory tests on rock fragments.The model results were verified with the subsidence and stress data recently collected from a longwall mine in the eastern United States.

关键词： Longwall mining Gateroad design Flac3D Horizontal angle Gob loading Hollow inclusion cells

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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

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Analysis of alternatives for using cable bolts as primary support at two low-seam coal mines

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international Journal of Mining Science and Technology 2016年第1期26卷 23-30页

作者： Esterhuizen Gabriel S. tulu ihsan b. Office of Mine Safety and Health Research NIOSH

Cable bolts are sometimes used in low-seam coal mines to provide support in difficult ground conditions.This paper describes cable bolting solutions at two low-seam coal mines in similar ground conditions.both mines used support systems incorporating cable bolts as part of the primary support system.Two original cable bolt based support systems as well as two modified systems are evaluated to estimate their ability to prevent large roof falls. One of the support systems incorporated passive cable bolts,while the other used pre-tensioned cable bolts. The results and experience at the mines showed that the modified systems provided improved stability over the original support systems. The presence of the cable bolts is the most important contribution to stability against large roof falls,rather than the details of the support pattern. it was also found that a heavy steel channel can improve the safety of the system because of the ‘sling' action it provides. Additionally,the analysis showed that fully-grouted rebar bolts load much earlier than the cable bolts,and pre-tensioning of the cable bolts can result in a more uniform distribution of loading in the roof.

关键词：电缆螺栓支护方案预应力锚索支撑系统支持系统压煤煤层开采

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Global prevalence and gender inequalities in at least 60 min of self-reported moderate-to-vigorous physical activity 1 or more days per week:An analysis with 707,616 adolescents

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Journal of Sport and Health Science 2024年第5期13卷 709-716页

作者： Raphael H.O.Araujo AndrúO.Werneck Clarice L.Martins Luciana L.barboza Rafael M.Tassitano Nicolas Aguilar-Farias Gilmar M.Jesus Robinson Ramírez-Véelez Riki Tesler Adewale L.Oyeyemi Ellen C.M.Silva Robert G.Weaver Mark S.Tremblay Javier brazo-Sayavera Grégore i.Mielke Danilo R.P.Silva Graduation Program in Health Sciences Londrina State University(UEL)Londrina 86057-970Brazil Center for Epidemiological Research in Nutrition and Health Department of NutritionSchool of Public HealthUniversidade de Sao Paulo(USP)Sao Paulo 01246-904Brazil Department of Physical Education Federal University of ParaıbaParaıba 58051-900Brazil Research Centre of Physical Activity Health and LeisureFaculty of SportsLaboratory for Integrative and Translational Research in Population Health(ITR)University of PortoPorto 4500Portugal Postgraduate Program in Physical Education University of BrasıliaBrasılia 70910-900Brazil Department of Kinesiology and Community Health University of Illinois at Urbana-ChampaignChampaignIL 61801-3841USA Department of Physical Education Sports and RecreationUniversidad de La FronteraTemuco 4680000Chile Department of Health State University of Feira de SantanaFeira de Santana 44036-900Brazil Navarrabiomed Hospital Universitario de Navarra(HUN)Navarra Institute for Health Research(IdiSNA)Universidad Publica de Navarra(UPNA)Pamplona 31006Spain Facultad de Ciencias de la Educacion Unidad Central del Valle del Cauca(UCEVA)TuluaValle del Cauca 763022Colombia Health Management Department Faculty of Heath sciencesAriel UniversityAriel 40700Israel College of Health Solutions Arizona State UniversityPhoenixAZ 85004USA Arnold School of Public Health University of South CarolinaColumbiaSC 29208USA Healthy Active Living and Obesity Research Group Children’s Hospital of Eastern Ontario Research InstituteOttawaON K1H 8L1Canada Department of Pediatrics University of OttawaOttawaON K1H 8L1Canada Department of Health Sciences Carleton UniversityOttawaON K1S 5B6Canada Department of Sports and Computer Science Universidad Pablo de Olavide(UPO)Seville 41013Spain Centro Universitario Regional Noreste Universidad de la RepublicaRivera 40000Uruguay School of Public Health The University of QueenslandBrisbaneQLD 4006Australia Department of Physical Education

background:Guidelines recommend that adolescents should accumulate an average of 60 min per day of moderate-to-vigorous physical activity(MVPA).However,using only this cut-off could hide important information.For instance,from a population-level point of view,increasing physical activity for those with no or low physical activity could provide more health benefits than increasing physical activity for those with intermediate levels.Also,including a more sensitive cut-point of≥1 days per week could be an additional strategy for identifying those with low access/opportunities for physical activity practice.Thus,the current study aims to estimate the prevalence of≥60 min of MVPA≥1 days per week among adolescents globally,and to describe any relevant gender inequalities.Methods:We used representative datasets from 146 countries/territories collected between 2003 and 2019.MVPA was self-reported.Participants were grouped into younger(≤14 years old)and older(>14 years old)adolescents.Crude Poisson regression models were used to identify the relative differences in≥60 min of MVPA≥1 days per week between boys and girls,and random-effects meta-analysis models were used to identify the pooled estimates.Analyses were stratified by country and region.Results:Approximately 80%of both younger and older adolescents reported≥60 min of MVPA≥1 days per week.This prevalence was≥94%in Europe and Central Asia and North America,while the estimates for the other regions werein of MVPA≥1 days per week was higher among boys than girls,with the largest differences occurring among the oldest adolescents(Prevalence ratio_(≤14y)=1.04(95%confidence interval(95%Ci)):1.03-1.04)vs.Prevalence ratio_(>14y)=1.09(95%Ci:1.08-1.10)).Conclusion:Approximately 8 out of 10 adolescents reported accumulating≥60 min of MVPA≥1 days per week,with notable differences between regions.Gender differences were observed in several countries,especially among the oldest adolescents.Priorities for physical activity promotion among adolescents

关键词： Global School-based Student Health Survey Health behaviour Among School-aged Children survey inequality Surveillance Youth

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纳米空间分辨率和毫秒时间尺度下观察细胞内细胞器和细胞骨架的互作

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科学新闻 2019年第2期 39-39页

作者：郭玉婷李迪 Siwei Zhang Yanrui Yang Jia-Jia Liu Xinyu Wang Chong Liu Daniel E.Milkie Regan P.Moore U.Serdar tulu Daniel P.Kiehart Junjie Hu Jennifer Lippincott-Schwartz Eric betzig 李栋中科院生物物理研究所

文章简介真核细胞内的各种细胞器之间以及和细胞器与细胞骨架之间时刻进行着高度动态却又有序的相互作用,这些相互作用可协调完成细胞内的复杂功能。观察这些相互作用需要对细胞的内环境进行非侵入式且长时间的高时空分辨率成像。为了... 详细信息

文章简介真核细胞内的各种细胞器之间以及和细胞器与细胞骨架之间时刻进行着高度动态却又有序的相互作用,这些相互作用可协调完成细胞内的复杂功能。观察这些相互作用需要对细胞的内环境进行非侵入式且长时间的高时空分辨率成像。为了实现这些看似相互矛盾的目标,课题组发展了掠入

关键词：细胞器结构光成像技术空间分辨率

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