Numerical simulation and application on blasting to improve gas drainage rate in floor rock of coal roadway

Abstract：The gas flow increases as cracks and vibrations in coal seam are produced by the deep-hole control blasting in rock adjoining soft coal seam in which drill hole was easily destroyed. In order to study the differences between biasting in rock and that in coal body, dynamic stress distributions and draining effect for different medium blasted were discussed by means of three-dimensional numerical simulation method and blasting test from the coal mine. The characteristics of drilling hole patterns which blasting hole was located in single coal body and in rock media were analyzed. Blasting models on the different condition were constructed by numerical simulation. Relationships between effective stress and distance at linking line between blasting hole and draining hole were studied for single coal seam and coal-rock media. The maximum of effective stress decrease 57% when the stress wave spread from rock to coal seam in the coal-rock media. While it＇ s only 27% in the single coal seam at the same location;gas draining effect was considerably affect by distribution of effective stress along axis of controlling holes. The mean effective stress along axis of the draining hole in coal-rock media, when the distance between blasting hole and controlling hole is 2. 0 m, is appropriately the same as that is 3.0 m in the single coal seam. These research conclusions were validated to be correct by the deep blasting which located in rock nearby coal seam in Yuyang Coal Mine.