Grant: Collaborative Research and Development Grants

Strainbursting is the unpredictable and often violent ejection of rock from the face or sidewalls of advancing drifts in deep mines in hard rock. With the increasing depth of many mines in Ontario, the incidence of these events is increasing, which is leading to increasing risk of injury to mine personnel. Over the years, techniques known as destressing, which normally involve blasting, have been developed to alleviate this problem. The objective of destress blasting is to alter the properties of the rock mass in such a way that high stresses at the excavation boundaries are reduced. There are competing explanations for the mechanisms of how this works (gas pressure vs creation of new fractures). Those mechanisms have not been clearly identified through measurement, nor have the conditions been identified which would trigger the use of destressing. As a result, current design of destressing blasts is entirely empirical.Given this state of uncertainty in the practice of drift destressing, there is a clear need to establish reliable guidelines for its design, implementation, and monitoring of effectiveness. Vale has initiated a research program with the applicant on destressing, which currently includes sponsorship of a part-time PhD student. This proposal seeks funding for two additional researchers at the Masters level. These projects will be part of the overall program whose objective is to develop practical guidelines for the use of destress blasting for drifts. It is proposed to carry out a series of blasting trials and full-scale destress blasts, to monitor their effects on the rock mass using various instruments, and to identify and rank the importance of the controlling parameters. These results will feed into the overall project, whose objectives are to develop practical guidelines that can be used by mining practitioners to reliably use destress blasting as a tool to improve worker safety in strainburst prone conditions. The results of this research will be applicable to all Canadian deep hard-rock mines.