Characteristics of electrical response and permeability law of coal mass under electric pulse

Improving the permeability of coal seam is the key factor to realize efficient and safe mining of coalbed gas. In order to study the effect of high-voltage pulse breakdown on coal permeability, the multi-field coupling high-voltage pulse crack coal permeability test equipment was used to carry out breakdown tests on bituminous coal samples soaked in conductive fluid under different voltage conditions. Subsequently, the breakdown effect of high voltage electrical pulse was characterized by comparison of breakdown energy, coal sample permeability and pore distribution, and the mechanism of voltage effect and the concentration of conductive liquid on the cracking effect was explored. The results show that the higher the pulse voltage, the faster the formation rate of plasma channel in coal and the more obvious the breakdown effect. With the increase of pulse voltage, the increment of coal porosity first increases and then decreases, the maximum increase is 31.4 %, and the cracking effect is obvious. By comparing the changes of permeability and pore distribution of coal samples before and after pulse voltage treatment, it is found that conductive liquid can improve the conductivity in fragile cracks, crack growth and pore connectivity under pulse voltage. This paper provides a basis for high voltage electric pulse as a method to enhance coal permeability.