Experimental study on the frequency dispersion response of composite electrical properties of coal

In order to study the characteristics of frequency dispersion response of the composite electrical properties of coal, the real part R and imaginary part X of the composite resistance of coal body at different direction in different measured areas were measured, the frequency dispersion characteristics were analyzed, different classical models were used to conduct data inversion and comparison. The results show that the composite electrical property parameters(absolute value of R and X) of coal are inversely proportional to the measured area, the characteristic frequency points are not offset, the X-frequency divergence decreases with the increase of measurement area; for the same measured area, the frequency dispersion response of the composite electrical property of coal at different direction is different, the frequency dispersion of the composite electrical curve deviates, the frequency dispersion of X parallel to coal bedding is greater than that vertical to bedding; Debye model and Cole-Cole model can be used to fit the dispersion curve of the composite electrical property of coal, but the former model has simple parameters and clear physical meaning, and coincides well the composite electrical frequency dispersion curve of coal. This study provides an experimental basis for monitoring the seam crack and evaluating coal seam permeability by the evaluation method of the composite electrical property.