Experimental Study on Damage Fracture Law of Coal from Solid-Propellant Blasting

Abstract

The low permeability of coal seams has always been the main bottleneck restricting coalbed methane drainage. In this paper, a coal seam anti-reflection technology with solid-propellant blasting was proposed, and the composition and proportion of the solid propellants were determined based on the principle of oxygen balance. The authors designed a solid-propellant blasting damage fracture experiment of simulation coal, tested the impact pressure on a blast hole wall, measured the ultrasonic wave velocity, explosive strain and crack propagation velocity, and then revealed the blasting damage fracture process and mechanism of coal based on the experimental results and damage fracture mechanics theory. The history curve of impact pressure time can be divided into three processes including the slow pressurization process, dramatic increase process, and nonlinear pressure relief process. The pressure distribution along the whole blasting hole was uneven, and the peak pressure was relatively small, but the pressure action time was long. The damage and fracture process of coal solid-propellant blasting can be divided into two stages including the rapid damage fracture development stage and the stable slow damage fracture development stage. Firstly, the explosion stress wave produced and rapidly accelerated the radial cracks extension; secondly, the cracks slowly expanded over a large area by the combined effects of the high-pressure gases, the gas, and the original rock stress.