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| 1 | Loading characteristics of mechanical rib bolts determined through testing and numerical modeling显示文摘Underground coal mines use mechanical bolts in addition to other types of bolts to control the rib deformation and to stabilize the yielded coal ribs.Limited research has been conducted to understand the performance of the mechanical bolts in coal ribs.Researchers from the National Institute for Occupational Safety and Health(NIOSH)conducted this work to understand the loading characteristics of mechanical bolts(stiffness and capacity)installed in coal ribs at five underground coal mines.Standard pull-out tests were performed in this study to define the loading characteristics of mechanical rib bolts.Different installation torques were applied to the tested bolts based on the strength of the coal seam.A typical tri-linear load-deformation response for mechanical bolts was obtained from these tests.It was found that the anchorage capacity depended mainly on the coal strength.Guidelines for modeling mechanical bolts have been developed using the tri-linear load-deformation response.The outcome of this research provides essential data for rib support design. | Khaled Mohamed Gamal Rashed Zorica Radakovic-Guzina | 2020 | International Journal of Mining Science and Technology2020，30，1： | 4 |
| 2 | Change of the mode of failure by interface friction and width-to-height ratio of coal specimens显示文摘Bumps in coal mines have been recognized as a major hazard for many years. These sudden and violent failures around mine openings have compromised safety, ventilation and access to mine workings.Previous studies showed that the violence of coal specimen failure depends on both the interface friction and width-to-height(W/H) ratio of coal specimen. The mode of failure for a uniaxially loaded coal specimen or a coal pillar is a combination of both shear failure along the interface and compressive failure in the coal. The shear failure along the interface triggered the compressive failure in coal. The compressive failure of a coal specimen or a coal pillar can be controlled by changing its W/H ratio. As the W/H ratio increases, the ultimate strength increases. Hence, with a proper combination of interface friction and the W/H ratio of pillar or coal specimen, the mode of failure will change from sudden violent failure which is brittle failure to non-violent failure which is ductile failure. The main objective of this paper is to determine at what W/H ratio and interface friction the mode of failure changes from violent to non-violent. In this research, coal specimens of W/H ratio ranging from 1 to 10 were uniaxially tested under two interface frictions of 0.1 and 0.25, and the results are presented and discussed. | Gamal Rashed Syd S.Peng | 2015 | Journal of Rock Mechanics and Geotechnical Engineering2015，7，3： | 3 |
| 3 | Wastewater treatment in horizontal subsurface flow constructed wetlands using different media (setup stage) 显示文摘 | Zidan A R A El - Gamal M M Rashed A A | 2015 | Water Science2015，50，1： | 1 |
| 4 | Coal rib response during bench mining: A case study显示文摘In 2016, room-and-pillar mining provided nearly 40% of underground coal production in the United States.Over the past decade, rib falls have resulted in 12 fatalities, representing 28% of the ground fall fatalities in U.S.underground coal mines.Nine of these 12 fatalities(75%) have occurred in room-andpillar mines.The objective of this research is to study the geomechanics of bench room-and-pillar mining and the associated response of high pillar ribs at overburden depths greater than 300 m.This paper provides a definition of the bench technique, the pillar response due to loading, observational data for a case history, a calibrated numerical model of the observed rib response, and application of this calibrated model to a second site. | Morgan M.Sears John Rusnak Mark Van Dyke Gamal Rashed Khaled Mohamed Michael Sloan | 2018 | International Journal of Mining Science and Technology2018，28，1： | 0 |
| 5 | A NEW CONCEPT AND EXHIBITION PROGRAM FOR THE EGYPTIAN MUSEUM IN CAIRO显示文摘This article presents a new concept for the future permanent display of the Egyptian Museum in Cairo, and discusses different practical ideas and concepts. Throughout the discussion, recent challenges and opportunities are considered, particularly the conflicts and duplication among the three major museums in Greater Cairo, the Egyptian Museum(EMC), the Grand Egyptian Museum(GEM), and the National Museum of Egyptian Civilization(NMEC). Different ideas are introduced, while selected options are then discussed. The author argues his suggestion to develop a concept that combines archaeological fieldwork, masterpieces, and visible storage in a presentation that varies from aesthetic, contextual and systematic display. This comes from the author's understanding of the expected audiences, their interests, the strengths of the collection, the exhibition space, and EMC's mission. | Mohamed Gamal Rashed | 2018 | Journal of Ancient Civilizations2018，33，1： | 0 |
| 6 | Preliminary rib support requirements for solid coal ribs using a coal pillar rib rating(CPRR)显示文摘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 ribs.The CPRR characterizes the rib composition and evaluates its impact on the inherent stability of the coal ribs.The CPRR utilizes four parameters:rib homogeneity,bedding condition,face cleat orientation with respect to entry direction,and rib height.All these parameters are measurable in the field.A rib data collecting procedure and a simple sheet to calculate the CPRR were developed.The 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 depth.CPRR calculations were conducted for 22 surveyed solid coal ribs,mainly composed of coal units.Based 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 cases.Two sample cases are presented that illustrate the data collection form and CPRR calculations. | Khaled Mohamed Mark Van Dyke Gamal Rashed Morgan MSears Robert Kimutis | 2021 | International Journal of Mining Science and Technology2021，31，1： | 0 |
| 7 | A coal rib monitoring study in a room-and-pillar retreat mine显示文摘The National Institute for Occupational Safety and Health(NIOSH)conducted a comprehensive monitoring program in a room-and-pillar mine located in Southern Virginia.The deformation and the stress change in an instrumented pillar were monitored during the progress of pillar retreat mining at two sites of different geological conditions and depths of cover.The main objectives of the monitoring program were to better understand the stress transfer and load shedding on coal pillars and to quantify the rib deformation due to pillar retreat mining;and to examine the effect of rib geology and overburden depth on coal rib performance.The instrumentation at both sites included pull-out tests to measure the anchorage capacity of rib bolts,load cells mounted on rib bolts to monitor the induced loads in the bolts,borehole pressure cells(BPCs)installed at various depths in the study pillar to measure the change in vertical pressure within the pillar,and roof and rib extensometers installed to quantify the vertical displacement of the roof and the horizontal displacement of the rib that would occur during the retreat mining process.The outcome from the monitoring program provides insight into coal pillar rib support optimization at various depths and geological conditions.Also,this study contributes to the NIOSH rib support database in U.S coal mines and provides essential data for rib support design. | Gamal Rashed Khaled Mohamed Robert Kimutis | 2021 | International Journal of Mining Science and Technology2021，31，1： | 0 |
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