|
Abstract In order to stduy the crack extension and mechanical characters of explosive blasting in different layers of coal-rock media and to increase the permeability of coal seam of low permeability in the deep hole pre-splitting blasting，a blasting simulation test system was set up in the laboratory. Two different charging modes of drilling borehole，cross and down the seam，were designed. Deep hole pre-splitting blasting test model was built based on Froude proportion method and the samples with the size of 50 cm×50 cm×50 cm were prepared with the similar materials. Under the above conditions，blasting simulation tests were carried out. The strain signals of coal rock were monitored with the super dynamic strain gauge. The whole process from the crack initiation，expansion and breaking through to the destruction of samples was recorded with the high speed camera. The dynamic mechanical and crack propagation properties under blasting loading were analyzed. The results showed that the cracks were mainly formed by the interaction of the compression and unloading waves and the direction of crack propagation was perpendicular to axis direction of hole. The effect of drilling blasting with borehole cross the seam was better than that down the seam. When the blasting stress wave was from the coal seam to the rock，the reflected tension shock wave was arisen to react on coal seam，which resulted in the aggravated damage of different coal-rock media and prompted blasting crack extension.
|
|
|
|
|
|
2016, Vol. 35 
