Coal strength and Young's modulus related to coal rank, compressional velocity and maceral composition

Pan, Jienan; Meng, Zhaoping; Hou, Quanlin; Ju, Yi‐Hsu; Cao, Yongzhi

doi:10.1016/j.jsg.2013.07.008

Cited by 86 publications

(52 citation statements)

References 30 publications

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“…In the current DEM analyses, the estimated force wave velocity of an intact rock block (≈1,300 m/s) matches well the lower bound wave velocity of real coal rocks (≈1,200 to 2,500 m/s for intact coal rocks under well‐controlled testing conditions; see Krzesińska, ; Morcote et al, ; Wu et al, ). In addition, according to Pan et al (), the compressive force wave velocity of rock, v p , can be estimated by a theoretical equation:

v_{p} = \sqrt{\frac{E_{normalb}}{ρ_{normalb}} \frac{(1 - ν)}{((), 1 + ν) ((), 1 - 2 ν)}}

where E b and ρ b are the bulk Young's modulus and density, respectively and ν is the Poisson's ratio of coal rock. ρ b can be computed from the sample porosity ( n ) and dry paticle density ( ρ s ) as

ρ_{b} = ((), 1 - n) ρ_{s}

…”

Section: Resultsmentioning

confidence: 99%

Dynamic Fragmentation of Jointed Rock Blocks During Rockslide‐Avalanches: Insights From Discrete Element Analyses

et al. 2018

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The dynamic fragmentation of jointed rock blocks during rockslide avalanches has been investigated by discrete element method simulations for a multiple arrangement of a rock block sliding over a simple slope geometry. The rock blocks are released along an inclined sliding plane and subsequently collide onto a flat horizontal plane at a sharp kink point. The contact force chains generated by the impact appear initially at the bottom frontal corner of the rock block and then propagate radially upward to the top rear part of the block. The jointed rock blocks exhibit evident contact force concentration and discontinuity of force wave propagation near the joint, associating with high energy dissipation of granular dynamics. The corresponding force wave propagation velocity can be less than 200 m/s, which is much smaller than that of an intact rock (1,316 m/s). The concentration of contact forces at the bottom leads to high rock fragmentation intensity and momentum boosts, facilitating the spreading of many fine fragments to the distal ends. However, the upper rock block exhibits very low rock fragmentation intensity but high energy dissipation due to intensive friction and damping, resulting in the deposition of large fragments near the slope toe. The size and shape of large fragments are closely related to the orientation and distribution of the block joints. The cumulative fragment size distribution can be well fitted by the Weibull's distribution function, with very gentle and steep curvatures at the fine and coarse size ranges, respectively. The numerical results of fragment size distribution can match well some experimental and field observations.

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v_{p} = \sqrt{\frac{E_{normalb}}{ρ_{normalb}} \frac{(1 - ν)}{((), 1 + ν) ((), 1 - 2 ν)}}

ρ_{b} = ((), 1 - n) ρ_{s}

…”

Section: Resultsmentioning

confidence: 99%

Dynamic Fragmentation of Jointed Rock Blocks During Rockslide‐Avalanches: Insights From Discrete Element Analyses

et al. 2018

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“…Uniaxial compressive strength and Young's modulus increase with coal rank. This is due to less microporous structure of higher rank coal (Pan et al, 2013). Also, studies show higher permeability with pore pressure depletion for the coal with higher lateral Young's modulus (parallel to bedding) (Danesh et al, 2016;Pan and Connell, 2011).…”

Section: Introductionmentioning

confidence: 99%

Characterisation of creep in coal and its impact on permeability: An experimental study

Danesh

Chen

Connell

et al. 2017

International Journal of Coal Geology

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ABSTRACT:Creep is a time-dependent deformation that affects coal permeability and should be considered in the prediction of Coalbed Methane (CBM) production. This study experimentally characterises and quantifies the impact of creep on coal permeability. The experiments were conducted on a bituminous coal sample, excavated from Bowen Basin, Australia, using a triaxial gas rig equipped with strain and displacement transducers. Two different types of gasses (helium and methane) were injected into the sample under various stress and pore pressure conditions. It was found that for the experiments with helium, creep caused permanent partial closure of cleats and pathways under constant effective stress, and hence a reduction in permeability. Under hydrostatic stress only, a Residual Deformation Ratio (RDR) of 14.1% and a Permeability Loss Ratio (PLR) of 71% were found following the removal of the axial load. This can be due to the damage to coal microstructure along with closure of cleats. For the experiments with methane, coal experienced an instantaneous elastic deformation, at the onset of pore pressure depletion, followed by consolidation and matrix shrinkage. Then, creep occurred when gas desorption ceased. A total permeability loss of 26% was achieved due to an increase of 1.91 MPa in effective stress caused by gas desorption. In addition, the model previously developed by authors was validated against the experimental permeability data. A good agreement was found between the model-predicted permeability data and the experimental permeability data, particularly for higher pore pressure ranges.Keywords: Coal permeability; creep; consolidation; triaxial test; gas desorption

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“…The soft coal has poor strength of extension, with a stretching strain lower than10 -4 in most cases, so the coal's tensile strain ε can be ignored [19]. The uniaxial compressive strength, elasticity modulus E and peak strain εp can be calculated via the formula below [20]. Porosity can be measured with the Poremaster 33 high pressure porosity apparatus, and it can be ascertained that porosity is the coal's initial damage D0.…”

Section: High-pressure Water Jet Cutting Radiusmentioning

confidence: 99%

Drainage Radius after High Pressure Water Jet Slotting Based on Methane Flow Field

Xia¹,

Zhao²,

Lu³

et al. 2016

IJHT

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Considering that the methane drainage radius cannot speedily and accurately be confirmed after high pressure water jet slotting, a model for slotting the radius of high pressure water jet slotting is established based on the theory of round turbulent jet and Loland damage model. Combining the linear seepage theory and nonlinear seepage theory, this paper proposes the seepage model for various seepage statuses around the slot. The methane drainage radius after using a high pressure water jet consists of three parts: slotting radius, linear seepage area and nonlinear seepage area. Taking Zhongliangshan Mine as an example, the calculated results show that the slotting radius is 1.57m. The linear seepage areas range from 1.57m to 4.81m, and the nonlinear seepage areas range from 4.81m to 9.36m from the center of borehole, respectively. Field experimentation shows that the radius of slotting reaches 1.5m. The effective drainage radius is 5m and the radius of influence is 9m. It is relatively consistent with the theoretical calculations.

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Coal strength and Young's modulus related to coal rank, compressional velocity and maceral composition

Cited by 86 publications

References 30 publications

Dynamic Fragmentation of Jointed Rock Blocks During Rockslide‐Avalanches: Insights From Discrete Element Analyses

Dynamic Fragmentation of Jointed Rock Blocks During Rockslide‐Avalanches: Insights From Discrete Element Analyses

Characterisation of creep in coal and its impact on permeability: An experimental study

Drainage Radius after High Pressure Water Jet Slotting Based on Methane Flow Field

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