Abstract
The split-Hopkinson pressure bar (SHPB) and digital image correlation (DIC) techniques are combined to analyze the dynamic compressive failure process of coal samples, and the box fractal dimension is used to quantitatively analyze the dynamic changes in the coal sample cracks under impact load conditions with different loading rates. The experimental results show that the fractal dimension can quantitatively describe the evolution process of coal fractures under dynamic load. During the dynamic compression process, the evolution of the coal sample cracks presents distinct stages. In the crack propagation stage, the fractal dimension increases rapidly with the progress of loading, and in the crack widening stage, the fractal dimension increases slowly with the progress of loading. The initiation of the crack propagation phase of the coal samples gradually occurs more quickly with increasing loading rate; the initial cracks appear earlier. At the same loading time point, when the loading rate is greater, the fractal dimension of the cracks observed in the coal sample is greater.
摘要
本文采用高速摄像与数字散斑法相结合的方法记录煤样动态破坏过程, 并通过图像处理对高速摄影捕捉到的试样图片进行裂隙提取, 采用盒分形维数定量描述煤样裂隙, 得到了不同加载率冲击载荷下煤样动态裂隙的分形维数变化特性. 结果表明, 分形方法可以有效地定量描述动载荷作用下煤样裂隙演化过程. 在动态加载过程中, 煤体裂隙演化呈现明显的阶段性; 在裂隙扩展阶段, 分形维数随着加载的进行迅速增大; 在裂隙宽度增加阶段, 分形维数随着加载的进行缓慢增大; 在动态加载过程中, 煤样裂隙扩展阶段时间随着加载率的增大而逐渐延长, 随着加载率的增大, 裂纹初始产生时间提早; 在相同的加载时间内, 分形维数随着加载率的增大而逐渐增大.
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The overarching research goals were developed by GAO Ming-zhong, LI Sheng-wei and CUI Peng-fei. ZHANG Jian-guo, WANG Man and WANG Ying-wei are responsible for on-site sampling and lithology analysis. GAO Ming-zhong, CUI Peng-fei, ZHANG Jian-guo and LI Sheng-wei analyzed the calculated results. The initial draft of the manuscript was written by GAO Ming-zhong and CUI Peng-fei. All authors replied to reviewers’ comments and revised the final version.
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GAO Ming-zhong, ZHANG Jian-guo, LI Sheng-wei, WANG Man, WANG Ying-wei and CUI Peng-fei declare that they have no conflict of interest.
Foundation item: Projects(51822403, 51827901) supported by the National Natural Science Foundation of China; Project(2019ZT08G315) supported by the Department of Science and Technology of Guangdong Province, China
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Gao, Mz., Zhang, Jg., Li, Sw. et al. Calculating changes in fractal dimension of surface cracks to quantify how the dynamic loading rate affects rock failure in deep mining. J. Cent. South Univ. Technol. 27, 3013–3024 (2020). https://doi.org/10.1007/s11771-020-4525-5
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DOI: https://doi.org/10.1007/s11771-020-4525-5