Study on the Law of Fracture Development in Plasma-Induced Broken Coal

The plasma-induced crushing technology is an efficient method for coal seam cracking. To study the law of fracture development in coal during plasma-induced breakage, this study established an experiment platform of plasma-induced breakage. With the aid of this platform, the macroscopic fracture development characteristics of coal were obtained using a scanning electron microscope and the computerized tomography scanning technology. Furthermore, the process of plasma-induced coal breakage was numerically simulated and analyzed based on the energy-equivalent method. The experimental results suggest that the plasma-induced breakage leads to the formation of a crushing circle around the electrode and multiple penetrated fractures on the coal surface. The radius of the crushing circle increases with the rise of discharge voltage. As can be observed from the slices, the law of fracture development within coal resembles that on the coal surface, but the position of fracture initiation deviates from the position of plasma channel. According to the development degree, the fracture area along the axial direction can be divided into three parts in a descending order: the positive electrode influence area, the negative electrode influence area and the interior fluctuation area. The electrical explosion effect of the plasma channel causes the generation of a shock wave that propagates along the radial direction and attenuates continuously in the coal body. Resultantly, the coal body around plasma channel forms a crushing area and a fracture area.