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

Li Donghui; Li Zixin; Li Zhe; Huang Yaping

doi:10.16186/j.cnki.1673-9787.2023120030

Abstract：Objectives To analyze the effects of water saturation,anisotropy,and pore structure on the com-plex electrical resistivity of coal and its dispersion characteristics,an experimental study on the complex re-sistivity anisotropy and dispersion characteristics of coal with different water saturations was carried out.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 an-isotropy coefficients were employed to quantify the influence of water saturation and porosity on the anisot-ropy 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 val-ues of Z and X decrease with the increasing water saturation,and the imaginary component X shows a sig-nificant shift.As water saturation increases,the interfacial critical frequency shifts towards higher frequen-cies.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.