Experimental Investigation of Stress Rate and Grain Size on Gas Seepage Characteristics of Granular Coal

Ma, Dexin; Li, Qiang; Hall, Matthew; Wu, Yu

doi:10.3390/en10040527

Cited by 32 publications

(26 citation statements)

References 29 publications

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“…After the yield stage, the mobilized shear stress increases to a peak value as roughness is mobilized and then keeps stable due to surface friction. The coal particles will continuously move and rotate under the action of the biting force or fiction [24]. The peak value defines the shear strength of the remodelled coal specimen, and a higher normal force implies a greater shear strength.…”

Section: Shear Stress-displacement Curvesmentioning

confidence: 99%

Coupled Effects of Moisture Content and Inherent Clay Minerals on the Cohesive Strength of Remodelled Coal

Zhang

Wan

et al. 2017

Energies

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Injecting water into a coal seam to enhance the cohesive strength of coal and thus minimize and reduce the coal wall spalling risk must be considered in underground coal mining systems. In general, coal with low cohesive strength contains clay minerals which may affect the stability of coal by interacting with water. Therefore, the coupled effects of moisture content and inherent clay minerals on the physical properties (i.e., cohesive strength and internal friction angle) of coal samples should be addressed. In this paper, direct shear tests were conducted by remodelling the Yiluo coal with various moisture contents ranging from 6.6% to 20.7%. According to Mohr-Coulomb failure criterion, cohesive strength and internal friction angle of coal were obtained. Afterwards, effects of moisture content and clay minerals (i.e., Kaolinite, Smectite and Illite) on the cohesive strength of coal were analysed using X-ray diffraction (XRD) method. The results show that cohesive strength increases when the moisture content rises from 6.6% to 17.6%, after which it decreases with increasing moisture content. This trend can be well illustrated by the relationship between typical water retention curve (WRC) and suction stress of soil. Therefore, a moisture content of 17.6% would be an optimal value to enhance the stability of the Yiluo coal seam.

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Section: Shear Stress-displacement Curvesmentioning

confidence: 99%

Coupled Effects of Moisture Content and Inherent Clay Minerals on the Cohesive Strength of Remodelled Coal

Zhang

Wan

et al. 2017

Energies

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“…The Forchheimer equation [19] has been verified to model the water seepage in granular rocks with good performance [23]. It was applied here to model the relation between the seepage velocity and the hydraulic pressure of SMM sample as…”

Section: Calculation Of the Non-darcy Hydraulicmentioning

confidence: 99%

Experimental Investigation on Hydraulic Properties of Granular Sandstone and Mudstone Mixtures

Cai

Zhou

et al. 2018

Geofluids

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The caved zone during longwall mining has high permeability, resulting in a mass of groundwater storage which causes a threat of groundwater inrush hazard to the safe mining. To investigate the hazard mechanism of granular sandstone and mudstone mixture (SMM) in caved zone, this paper presents an experimental study on the effect of sandstone particle (SP) and mudstone particle (MP) weight ratio on the non-Darcy hydraulic properties evolution. A self-designed granular rock seepage experimental equipment has been applied to conduct the experiments. The variation of particle size distribution was induced by loading and water seepage during the test, which indicated that the particle crushing and erosion properties of mudstone were higher than those of sandstone. Porosity evolution of SMM was strongly influenced by loading (sample height) and SP/MP weight ratio. The sample with higher sample height and higher weight ratio of SP achieved higher porosity value. In particular, a non-Darcy equation, for hydraulic properties (permeability and non-Darcy coefficient ) calculation, was sufficient to fit the relation between the hydraulic gradient and seepage velocity. The test results indicated that, due to the absence and narrowing of fracture and void during loading, the permeability decreases and the non-Darcy coefficient increases. The variation of the hydraulic properties of the sample within the same particle size and SP/MP weight ratio indicated that groundwater inrush hazard showed a higher probability of occurrence in sandstone strata and crushed zone (e.g., faults). Moreover, isolated fractures and voids were able to achieve the changeover from self-extension to interconnection at the last loading stage, which caused the fluctuation tendency of and . Fluctuation ability in mudstone was higher than that in sandstone. The performance of an empirical model was also investigated for the non-Darcy hydraulic properties evolution prediction of crushing and seepage processes. The predictive results indicated that particle crushing and water erosion caused the increase of hydraulic properties, being the main reason that the experimental values are typically higher than those obtained from the predictive model. The empirical model has a high degree of predictive accuracy; however, has a higher predictive accuracy than . Furthermore, the predictive accuracy of increases and decreases with increasing weight ratio of SP.

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“…Recently, increasing attention has been paid to gas‐flow characterization of crushed coal under constant axial load. The gas‐flow apparatus using nitrogen as fluid was developed by Ma and Chu separately, and the high‐speed non‐Darcy gas‐flow properties of crushed coal were investigated by their studies …”

Section: Introductionmentioning

confidence: 99%

The correlation between crushed coal porosity and permeability under various methane pressure gradients: a case study using Jincheng anthracite

Feng

Jiang

et al. 2018

Greenhouse Gases

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As a greenhouse gas (GHG), methane (CH4) emitted from underground mines contributes 17% to total anthropogenic greenhouse gas emissions. Gas drainage is the main measure to resolve this problem, and knowledge of methane flow in surrounding coal and rocks greatly influences our thinking and handling strategies for reducing CH4 emissions. However, due to the lack of matched testing systems, current studies are generally confined to considering methane flow properties in porous and fractured coal and rocks, whereas methane flow behaviors in crushed coal have not been extensively studied and understood yet. In this study, the relationships between crushed coal porosity and permeability under various methane pressures are investigated using a self‐designed gas permeation testing system, and continuous measurements of methane pressure and flow rate have been conducted. The results show that the permeability properties of crushed coal are closely related to the coal porosity, methane pressure, and axial stress. Darcy flow transfers to slip flow in crushed coal in the latter stage of coal‐mine methane drainage in crushed coal, and the permeability of crushed coal has a magnitude of 10−12–10−11 m2, which is rather larger than that of porous and fractured coals. The pseudo‐threshold pressure gradient (TPG) decreases with the growth of porosity, and it is rather smaller than that of lower permeability reservoirs (LPR). With an increase in methane pressure, the permeability of crushed coal presents a logarithmic growth trend; by contrast, it displays an exponential growth trend with an increase in porosity. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd.

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Experimental Investigation of Stress Rate and Grain Size on Gas Seepage Characteristics of Granular Coal

Cited by 32 publications

References 29 publications

Coupled Effects of Moisture Content and Inherent Clay Minerals on the Cohesive Strength of Remodelled Coal

Coupled Effects of Moisture Content and Inherent Clay Minerals on the Cohesive Strength of Remodelled Coal

Experimental Investigation on Hydraulic Properties of Granular Sandstone and Mudstone Mixtures

The correlation between crushed coal porosity and permeability under various methane pressure gradients: a case study using Jincheng anthracite

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