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In this study, an upscaling framework was developed to integrate the multiscale hydrogeological properties of roof aquifers in the coal mine, including microscopic pores, core-scale fracture geometry, and field-scale fracture distributions, for predicting water inflow from roof sandstone aquifers to mines. The 2 # coal roof …
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NIOSH has investigated roof failure in a number of coal mines in order to illustrate the causes and conditions leading up to a roof fall. Roof fall surveillance data indicate that a …
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An underground coal mine section has 35cm of sandstone in the roof underlain by three (3) shale bands each 5cm thick, and eleven (11) mudstone bands each 80mm thick. Design the support for this section using …
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The instability of underground spaces in abandoned coal mines with water-immersed rocks is one of the main hazards hindering the geothermal energy use and …
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Some sandstone roof falls occur along inclined bedding, such as these examples from the Jellico and Harlan coal beds in eastern Kentucky. Trends: Local falls in sandstone generally occur along bedding weaknesses, which may follow overall bed dip or may be caused by internal scours. Some sandstones are actually composites of different …
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2.1 Experiments 2.1.1 Sample Preparation. Coal and roof sandstone taken from an underground coal mine in Shanxi Province, China, at a depth of about 500 m were utilized. The rock blocks were processed into cylindrical samples with a diameter of 50 mm and a height of 100 mm (as shown in Fig. 1).Three samples were prepared and tested …
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and roof fall rate at six U.S. mines [Mark et al. 1994]. Figure 8.—Stress on a typical element of mine roof. The overburden load, on the other hand, is primarily carried by the pillars, but it can affect the immediate roof stability (and thus support loading) byC $ Causing sloughage of the pillars, thereby increasing the roof span in the mine ...
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The sandstone generates current and voltage, which indicates the existence of charge flow in the coal mine roof sandstone during mining. The property can provide experimental basis for the mechanism of electromagnetic radiation and the …
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Roof bolting in coal mines began on a modest scale in the early 1950s. Since then, the design of bolts, grout systems, accessories and installation techniques has improved significantly. Currently, roof bolting is the primary means of supporting mine roof in room-and-pillar operations in the bituminous coal sector. Although roof support …
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In view of the research situation and existing problems involved with the hard and stable roof control in coal mine,the test of directional hydraulic fracturing employed for the roof control is presented;the characteristics of hydraulic fracturing in the roof are obtained via the monitoring boreholes decorated on both sides of the fracturing borehole and the …
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Combined with the comprehensive analysis of the electrical generation and discharge and spark characteristics of the coal mine roof sandstone in Section 3, it can be concluded that when the original stress equilibrium …
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Sparks produced by the Renlou coal mine roof sandstone in low light. 4. Conclusion. In this study, the electric discharge characteristics during the deformation and fracture of the roof sandstone and the characteristics of the disaster caused by electric spark ignition of the gas were studied. The main conclusions are as follows:
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Variable Roof Rock – Sandstone, Shale, and Coal Interspersed. 4 • Coal has been mined in the United States for more than 200 years. Most of today's ... By recognizing and understanding these issues and conditions that continue to make coal mine roof and ribs so hazardous, we can begin to make progress in finding better ways to prevent ...
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Coal mine roof that falls before the installa tion of roof bolts can be hazardous. From 1995-2008, 24 . ... The mine maps sandstone in the roof and has identified complete coal seam .
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Immediate roof material in a certain coal mine comprises of a sandstone layer 40cm thick and is overlain by 1.5m of another rock type more stronger/competent than the sand stone. Sandstone has tensile strength of 5Mpa and density of 2.5t/m3. Advise the mine manager on the maximum cut-out distance based on the factor of safety of 2
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This research is intended to guide Quinsam Coal and other coal mines globally in efforts to develop or optimize coal extraction and address the geomechanical challenges …
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This study explores the discharge and ignition characteristics of roof indentation fracture to identify the real ignition source of a gas explosion in a coal mine goaf. Theoretical and experimental analyses conclude that the charge of the coal mine roof sandstone will gradually escape from the surface during the loading process.
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The sandstone samples were collected from the No. 4 coal seam roof of the Panbei Coal Mine in Huainan and Huaibei Mining Area, China. Unweathered …
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Figure 1.–Injuries caused by the fall of roof and rib in U.S. coal mines, 1983-99. Figure 2.–Fatalities caused by the fall of roof and rib in U.S. coal mines, 1983-99. safety and productivity. These structures weaken the roof beam and can cause damage that is not prevented by conventional roof support. In addition, the occurrence of the
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ASSESSING COAL MINE ROOF STABILITY THROUGH ROOF FALL ANALYSIS By Gregory M. Molinda,1 Christopher Mark, Ph.D.,2 and Dennis Dolinar3 ABSTRACT In 1999, 2,087 unplanned roof falls were reported from 841 mines. Nearly 55% of all mines reported at least one roof fall, and nearly 17% of the mines reported five or more falls. …
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sandstone may also reduce roof strength by increasing the shale's moisture content. In addition, since sandstones are generally much stiffer than shale, they may concentrate …
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A roof of a particular coal mine comprises of interlaminated shale/mudstone bands ( 13, 14,16,20,15 and 19) cms overlain by competent sandstone layer 1m thick.Given that;Hole diameter is 26mmBolt diameter 20mmSteel strength 600MPaRoadwidth 7.0mSandstone UTS 5MPaSandstone density 2650kgm3Take note that a pull test was …
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Direct in-mine measurements of horizontal stress in Illinois Basin mines, mostly in roofs above the two study coals, have found a range in magnitudes from 1,207 to 3,191 psi and orientations from ...
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This article is based on the engineering background of the 11,618 (east) working face in the Xieqiao Coal Mine and uses theoretical analysis methods to establish a model of the roof structure under a hard sandstone roof. The distribution pattern of the abutment stress near the end of the working face before and after roof cutting was …
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1. Immediate roof material in a certain coal mine comprises of a sandstone layer 40cm thick and is overlain by 1.5m of another rock type more stronger/competent than the sand stone. Sandstone has tensile strength of 6Mpa and density of 2.5t/m3. Advise the mine manager on the maximum cut-out distance based on the factor of safety of 1.2.
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To explore the causes of mine tremors in coal mines with sandstone roofs, a three-point bending loading experiment was designed for composite sandstone layers, and the fracture and interlayer shear slip characteristics of the composite sandstone layers were studied using optical measurement and acoustic emission techniques. The …
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Weak sandstone can cause roof falls in underground coal mines (from Greb and Cobb, 1987). Potential roof-fall hazards: Roof quality is usually good in sandstone, but local weaknesses can occur along …
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This paper provides a case study in machine learning using Artificial Neural Network (ANN) and geophysical log data information from an underground coal mine …
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WORKOUTImmediate roof material in a certain coal mine comprises of a sandstone layer 40cm thick and isoverlain by 1.5m of another rock type more stronper/competent than the sand stone. Sandstone hastensile strength of 5Mpa and density of 2.5tm3.
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The carbonate cement in the sandstone reservoir of the coal seam roof was formed by the decarboxylation of organic acid. The organic acid, containing CO 2 generated by coal rock hydrocarbon generation, has modified the tight sandstone reservoir of the coal seam roof via dissolution. This has improved the physical properties and pore …
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