Experimental study on hydraulic blasting stress wave propagation and coal broken mechanism

The similarity simulation experiment on hydraulic blasting stress wave propagation and coal broken mecha- nism was conducted in this study. The super dynamic strain measurement system was used to collect strain produced in coal seam. The propagation and attenuation of hydraulic blasting stress wave in coal was studied. The damage area and crack shape were comprehensively evaluated. The coal broken mechanism of hydraulic blasting was studied. The blas- ting effects of water and air that was non-coupling medium were analyzed comparatively,which proved the advantages of hydraulic fracturing. The results showed that coal body was broken in the means of plastic compression destruction first,forming a pulverizing zone around the blast hole with a radius of about 1. 5 times of the radius of the blast hole; then was broken in the means of brittle stretch destruction,forming a wide range of fracture zone with a radius of about 13 times of the radius of the blast hole;and finally stress wave was attenuated as seismic waves,causing the coal physi- cal point of elastic vibration and forming the blasting loose area.