Investigating blast fume propagation, concentration and clearance in underground mines using computational fluid dynamics (CFD)

Blasting activities using standard industry explosives is an essential component of underground hard rock mining operations. Blasting operations result in the release of noxious gases, presenting both safety and productivity threats. Overestimation of post-blast re-entry time results in production losses, while underestimation leads to injuries and fatalities. Research shows that most underground mines simply standardize post-blast re-entry times based on experiences and observations. Few underground mines use theoretical methods for calculating post-blast re-entry time. These theoretical methods, however, are unable to account for the variations in the blasting conditions. Literature review shows that: (i) there is currently no means of estimating safe blast distance (i.e., blast exclusion zone); and (ii) there is a lack of a comprehensive relationship for calculating optimal post-blast re-entry time and optimal air quantity in underground mines. An important factor associated with blast fume dilution and clearance, the fan duct discharge location, needs to be studied in details. To achieve the above goals, the computational fluid dynamics (CFD) method is used to simulate blast fume dispersion and clearance in the underground mine. An experiment has been successfully conducted at the Missouri S&T Experimental Mine to acquire blast data to validate the proposed CFD model. Computational fluid dynamics simulation results compare favorably with blast data from Missouri S&T Experimental Mine with a coefficient of determination (R2) of 0.97. Based on the verified CFD model, various blasting and ventilation conditions were studied. A linear relationship has been developed and validated for estimating safe blast distances. Four equations have been generated and validated to conservatively calculate optimal air quantity and post-blast re-entry time based on commonly used blasting and ventilation conditions --Abstract, page iii