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

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  • Dan Ma

    (School of Resources & Safety Engineering, Central South University, Changsha 410083, Hunan, China
    State Key Laboratory for Geomechanics & Deep Underground Engineering, China University of Mining & Technology, Xuzhou 221116, Jiangsu, China
    GeoEnergy Research Centre (GERC), University of Nottingham, Nottingham NG7 2RD, UK)

  • Qiang Li

    (State Key Laboratory for Geomechanics & Deep Underground Engineering, China University of Mining & Technology, Xuzhou 221116, Jiangsu, China)

  • Matthew R. Hall

    (GeoEnergy Research Centre (GERC), University of Nottingham, Nottingham NG7 2RD, UK
    British Geological Survey, Environmental Science Centre, Keyworth, Nottingham NG12 5GG, UK)

  • Yu Wu

    (State Key Laboratory for Geomechanics & Deep Underground Engineering, China University of Mining & Technology, Xuzhou 221116, Jiangsu, China)

Abstract

Coal seam gas, held within the inner pores of unmineable coal, is an important energy resource. Gas release largely depends on the gas seepage characteristics and their evolution within granular coal. To monitor this evolution, a series of experiments were conducted to study the effects of applied compressive stress and original grain size distribution (GSD) on the variations in the gas seepage characteristics of granular coal samples. Grain crushing under higher stress rates was observed to be more intense. Isolated fractures in the larger diameter fractions transformed from self–extending to inter-connecting pathways at a critical compressive stress. Grain crushing was mainly caused by compression and high-speed impact. Based on the test results of the original GSD effect, the overall process of porosity and permeability evolution during compression can be divided into three different phases: (1) rapid reduction in the void ratio; (2) continued reduction in the void ratio and large particle crushing; and (3) continued crushing of large particles. Void size reduction and particle crushing were mainly attributed to the porosity and permeability decreases that occurred. The performance of an empirical model, for porosity and permeability evolution, was also investigated. The predictive results indicate that grain crushing caused permeability increases during compression, and that this appeared to be the main cause for the predictive values being lower than those obtained from the experimental tests. The predictive accuracy would be the same for samples under different stress rates and the lowest for the sample with the highest proportion of large grain diameters.

Suggested Citation

  • Dan Ma & Qiang Li & Matthew R. Hall & Yu Wu, 2017. "Experimental Investigation of Stress Rate and Grain Size on Gas Seepage Characteristics of Granular Coal," Energies, MDPI, vol. 10(4), pages 1-15, April.
  • Handle: RePEc:gam:jeners:v:10:y:2017:i:4:p:527-:d:95713
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    Citations

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    Cited by:

    1. Hongwei Zhang & Zhijun Wan & Dan Ma & Bo Zhang & Peng Zhou, 2017. "Coupled Effects of Moisture Content and Inherent Clay Minerals on the Cohesive Strength of Remodelled Coal," Energies, MDPI, vol. 10(8), pages 1-12, August.
    2. Dan Ma & Zilong Zhou & Jiangyu Wu & Qiang Li & Haibo Bai, 2017. "Grain Size Distribution Effect on the Hydraulic Properties of Disintegrated Coal Mixtures," Energies, MDPI, vol. 10(5), pages 1-17, April.
    3. Weitao Liu & Yueyun Qin & Xiangxi Meng & Lifu Pang & Mengke Han & Zengmou Song, 2021. "Basic Experimental Study of Plasticity Material for Coal Rock Fracture Grouting Based on RSM-PCA Technology," Energies, MDPI, vol. 14(15), pages 1-20, July.
    4. Zhen Li & Guorui Feng & Haina Jiang & Shengyong Hu & Jiaqing Cui & Cheng Song & Qiang Gao & Tingye Qi & Xiangqian Guo & Chao Li & Lixun Kang, 2018. "The correlation between crushed coal porosity and permeability under various methane pressure gradients: a case study using Jincheng anthracite," Greenhouse Gases: Science and Technology, Blackwell Publishing, vol. 8(3), pages 493-509, June.
    5. Chao Wang & Qiangyong Zhang & Wen Xiang, 2017. "Physical and Numerical Modeling of the Stability of Deep Caverns in Tahe Oil Field in China," Energies, MDPI, vol. 10(6), pages 1-14, June.

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