Advanced blast modeling for mining steeply dipping coal seams

Most coal deposits in Western Canada involve steeply dipping multiple seams. An efficient way to recover coal seams would be to drill through the seams and blast both the overlying and underlying waste material in one shot without disrupting the coal seams while fragmenting the waste rock for easy removal. This requires special blasting techniques as reported by Chung and Jorgenson in 1985. This paper will describe the use of the advanced blast modeling code DMC_BLAST to determine the stand-off distance for loading explosives into a borehole, so that the displacement of blasted waste wedges can be controlled to achieve minimum disruption to coal seams. To calibrate the model for a site-specific application, a high-speed motion analysis of a typical blast was carried out to determine the energy damping factor for the blasted material. The blasted material can be an inter-bedded structure having: (1) layers dipping into the bench face, and (2) layers dipping away from the bench face. This program employs explicit time integration and uses spherical or cylindrical elements that are represented as circles in two dimensions (2-D). DMC_BLAST calculations compare favorably with data from actual bench blasts (Preece et al., 1993). A demonstration comparing the animated computer blast simulation with the digitized high-speed blast video is also given in the paper.