MULTIFRACTAL CHARACTERIZATION OF THE INHOMOGENEOUS STRAIN EVOLUTION OF THE DEHYDRATED COAL: INSIGHT FROM COAL MICROSTRUCTURE

Fractals Pub Date : 2024-02-22 DOI:10.1142/s0218348x24500361
JUNJUN FENG, CHUANHUA XU, FENG YU, JUN PENG, QISONG HUANG, PENG JIN
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Abstract

Underground coal mining in China has gradually moved into deeper seams in recent years, which results in a higher ambient temperature in the mining space and significantly affects the mechanical behavior of coal. In this study, dehydrated coal samples were obtained at different temperatures ranging from 30 to 70, and the mechanical behavior of the dehydrated coal was investigated through compressive loading tests. The digital image correlation (DIC) method was used to acquire the strain field of coal, and a multifractal analysis was conducted to characterize the strain evolution of coal. The findings suggest that the increasing temperatures result in higher moisture desorption rates and greater volumetric contraction strain in coal. Furthermore, coal with higher moisture desorption exhibits higher peak stress and peak strains when subjected to compressive loading. The multifractal analysis of the inhomogeneous strain evolution indicates a gradual decrease in the parameter Δα under compressive loading, followed by a sudden increase before reaching the failure point due to strain localization. The multifractal mechanism was further investigated, revealing that the inhomogeneous strain field of coal is inherently affected by the microstructure of coal. In addition, a mathematical model was proposed to elucidate the relationship between the inhomogeneous coal strain and the microstructure of coal. The result indicates that the inhomogeneity of the coal strain is directly associated with the multifractal singularity of the coal microstructure. Finally, the feasibility of using the multifractal parameter Δα to identify coal strain localization has been demonstrated, indicating its potential value in aiding engineers to determine the SLZ in deep coal mines.

脱水煤不均匀应变演变的多分形特征:煤炭微观结构的启示
近年来,中国的地下煤炭开采逐渐向深煤层转移,导致开采空间的环境温度升高,对煤炭的力学行为产生了显著影响。本研究在 30 ∘ 至 70 ∘ 的不同温度下获取了脱水煤样,并通过抗压加载试验研究了脱水煤的力学行为。采用数字图像相关(DIC)方法获取了煤的应变场,并进行了多分形分析以描述煤的应变演变特征。研究结果表明,温度升高导致煤的水分解吸率升高,体积收缩应变增大。此外,水分解吸率越高的煤炭在承受压缩载荷时,会表现出更高的峰值应力和峰值应变。对不均匀应变演变的多分形分析表明,在压缩荷载作用下,参数Δα逐渐减小,随后由于应变局部化,在达到破坏点之前突然增大。进一步研究了多分形机制,发现煤的不均匀应变场受到煤的微观结构的内在影响。此外,还提出了一个数学模型,以阐明煤的非均质应变与煤的微观结构之间的关系。结果表明,煤应变的不均匀性与煤微观结构的多分形奇异性直接相关。最后,利用多分形参数Δα来识别煤炭应变局部性的可行性也得到了证实,这表明它在帮助工程师确定深部煤矿的SLZ方面具有潜在价值。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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