WorldWide Drilling Resource

Boosting Blasting Safety in Reactive Ground Compiled by the Editorial Staff of WorldWide Drilling Resource ® Blasting safety is of utmost importance, especially in reactive ground. Sulphide-bearing ground presents significant risks when using ammonium nitrate-based explosives. The problem of reactive ground is often encountered when drilling in shale overburden in coal deposits and in the coal seams themselves. Fine sulphides created by drilling can dissolve in the water in the blasthole, raising its acidity. This acidic water can, in turn, react with normal emulsion explosive, causing it to heat up and potentially risk the performance of the blast - perhaps even resulting in unplanned detonation. More common than realized, reactive ground requires effective management, but it can be difficult to identify - often occurring only in pockets around a mine site. The risk can be further aggravated by conditions of acidity and rock weathering. Some indicators of sulphide- bearing rock are white and yellow salt staining on exposed rock and faces, or water vapor being emitted from blastholes. There could also be spontaneous combustion observed in ore stockpiles, or the presence of sulphide dioxide gas - as well as acidic water conditions and evi- dence of corrosion on the site. Blasting products company BME has developed a specialized emulsion explosive formu- lation for reactive ground - INNOVEX RG - which has been successfully used in SouthAfrican and Zambian mines. The product contains additives to inhibit exothermic reactions (which release heat or energy) in ground containing sulphides and/or other reactive materials. The formula- tion allows for safer operations. BME Senior Product Manager Rakhi Pathak said, “We have evolved our emulsion explosives and our testing methodology to deal with the risks posed by reactive ground.” Another challenge for mines is they seldom have the equipment or experience to identify and test for reactive ground - and this is where BME’s service has evolved significantly in recent years. Pathak said, “We are geared up with relevant on-site scientific tools and facili- ties to screen and test the rock, make the necessary findings on the type of ground being blasted, and recommend the right product.” BME’s toolkit includes the use of handheld XRF (X-ray fluorescent) metal analyzers for screening and initial analysis. The company’s mobile laboratory facilities can be deployed on-site for ground testing to determine the rock’s inter- action with various emulsion explosives. Simulation of minesite conditions in the laboratory enables testing the level of exothermic reaction before specifying the most suitable emulsion mix. Test results can indicate where reactive ground may present challenges, avoiding the risk of discovering the problem only after the emulsion has been pumped into the blastholes. BME Global Manager for Blasting Science Scott Scovira emphasized the right blast management practices must be in place to ensure safer blasting in reactive ground conditions. Four key critical controls are necessary: site-specific risk assessment to identify conditions and define controls for blasting in reactive ground; mine-defined site-specific blasting procedures, detailing the operational steps and controls for blasting in reactive ground; an operations audit to ensure conformance to the specified procedures, so any gaps can be identified and closed; personnel training to make blasting operations staff and supervisors aware of the risks associated with blasting reactive ground and drive home the importance of adhering to procedures and controls. EXB 12 DECEMBER 2021 WorldWide Drilling Resource ® RENEW - SUBSCRIBE NOW!