LI D H, LI Z X, LI Z,et al. Experimental study on anisotropy and dispersion characteristics of complex resistivity of coal with varying water saturation levels[J].Journal of Henan Polytechnic University(Natural Science) ,2025,44(6):147-155.

doi:10.16186/j.cnki.1673-9787.2023120030

Received: 2023/12/11

Revised: 2024/06/04

Published: 2025/10/14

Experimental study on anisotropy and dispersion characteristics of complex resistivity of coal with varying water saturation levels

Li Donghui1,2,3, Li Zixin1,2,3, Li Zhe1,2,3, Huang Yaping4

1.State Key Laboratory Cultivation Base for Gas Geology and Gas Control， Henan Polytechnic University， Jiaozuo  454000， Henan， China；2.School of Safety Science and Engineering， Henan Polytechnic University， Jiaozuo  454000， Henan， China；3.Collaborative Innovation Center for Coal Mine Safety Production and Clean Efficient Utilization， Ministry of Education and Henan Province， Jiaozuo  454000， Henan， China；4.School of Resources and Geosciences， China University of Ming and Technology， Xuzhou  221116， Jiangsu， China

Abstract: Objectives To analyze the effects of water saturation， anisotropy， and pore structure on the complex electrical resistivity of coal and its dispersion characteristics. Methods Anthracite samples from Zhaoguer Mine were selected to investigate their electrical properties. The complex impedance magnitude Z（representing actual energy dissipation） and the imaginary component X （representing energy storage capacity within the medium） were measured along different directions and under varying water saturation conditions. Corresponding complex resistivity spectrum were derived and anisotropy coefficients were employed to quantify the influence of water saturation and porosity on the anisotropy behavior of the coal samples.  Results The results show that the complex resistivity of water-saturated coal exhibits frequency dispersion i.e. the magnitude varies with frequency. Specifically， the absolute values of Z and X decrease with the increasing water saturation， and the imaginary component X shows a significant shift. As water saturation increases， the interfacial critical frequency shifts towards higher frequencies. The complex resistivity of coal exhibits pronounced anisotropy across different water saturation levels. The anisotropy coefficient increases with increasing water saturation and also rises with higher porosity， a behavior primarily attributed to the pore structure and its spatial distribution of the coal. Conclusions This study demonstrates a close linkage between water saturation， pore structure， and the anisotropy and frequency-dispersion characteristics of complex resistivity in coal. It provides experimental and theoretical basis for leveraging complex electrical properties to evaluate coal-seam pore structure， development state， and mineral composition and it offers practical implications for the prevention and control of coal-mine gas hazards.

Key words: water-bearing coal sample; water saturation; resistivity anisotropy; complex resistivity; anisotropy coefficient