Study on Cracks Extension of Coal Under Pulse Load

For low efficiency of extracting coalbed methane from low permeability coal seams, based on the theory of fracture stress intensity factor in fracture mechanics, we use RFPA-Dynamic numerical simulation to analyze the stress of coal samples’ cracks and the laws of their crack propagation under simulative ground stress, and take high voltage electric hydraulic fracturing technique and CT scanning technique to make fracturing experiments of the coal samples, at the same time, we study the effect of cracks and the evolution laws of crack propagation. The results show that the texture of the raw coal is hard and the primary joints are undeveloped; under the action of hydrostatic pressure and the high voltage electric shock loading, coal samples are easy to be damaged, and there are penetrating main cracks and branch cracks in the coal samples with a higher number and longer extension length; while under the action of high-voltage pulse wave, the tensile stress of the crack tip is large, the stress concentration occurs, and the cracks are easy to produce and develop. which proves that fracturing effect of coal under the action of high-voltage pulse is obvious, so this method is reliable and this technique is workable.