In this paper, an experimental study of the variation of resistivity of coal samples in different bedding directions at 1 MHz frequency was performed by establishing an experimental system for resistivity testing of coal under triaxial stress. The low-pressure nitrogen gas adsorption (LP-N₂GA) experiment and scanning electron microscopy (SEM) were obtained to analyze the pore-fracture structural characteristics of coal samples and the influence on resistivity anisotropy. Furthermore, the fundamental cause of anisotropy of coal resistivity is expounded systematically. The results show that the resistivity of loaded coal decreased first before increasing. The ionic conductance and the high degree of metamorphism slow down the decrease of resistivity. The distribution of pore and fracture structures is anisotropic. The connected pores and fractures are mainly distributed along the parallel bedding direction. The weak plane of bedding, diagenetic fractures, and plane fracture structures of parallel bedding result in the increase of fractures in the direction of vertical bedding, so increasing the potential barrier. Therefore, the resistivity in the vertical bedding direction is higher than that of the parallel bedding. Loading coal resistivity anisotropy degree is a dynamic change trend; the load increases anisotropy significantly under axial pressure, and the degree of anisotropy has a higher discreteness under confining pressure. It is mainly the randomness of the internal pore-fracture compaction, closure, and development of the heterogeneous coal under the confining pressure; the more rapid the decline in this stage, the larger the stress damage degree.

中文翻译：

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煤样电阻率各向异性分析

通过建立一个三轴应力下煤电阻率测试实验系统，对煤层样品在1MHz频率上不同层理方向的电阻率变化进行了实验研究。低压氮气吸附（LP-N ₂进行了GA实验和扫描电子显微镜（SEM）分析煤样品的孔隙-断裂结构特征及其对电阻率各向异性的影响。此外，系统地阐述了煤电阻率各向异性的根本原因。结果表明，加载煤的电阻率先下降先增加。离子电导率和高度的变质作用减慢了电阻率的下降。孔隙和裂缝结构的分布是各向异性的。连通的孔隙和裂缝主要沿平行的顺层方向分布。顺层的薄弱平面，成岩断裂和平行顺层的平面断裂结构导致沿垂直顺层方向的裂缝增加，从而增加了势垒。因此，垂直层理方向的电阻率高于平行层理的电阻率。装煤电阻率各向异性度是一个动态变化的趋势; 载荷在轴向压力下显着增加了各向异性，并且在密闭压力下各向异性程度具有较高的离散性。主要是围压作用下非均质煤内部孔隙裂缝的压实，封闭和发育的随机性。在此阶段下降越快，应力破坏程度越大。主要是围压作用下非均质煤内部孔隙裂缝的压实，封闭和发育的随机性。在此阶段下降越快，应力破坏程度越大。主要是围压作用下非均质煤内部孔隙裂缝的压实，封闭和发育的随机性。在此阶段下降越快，应力破坏程度越大。