Breaking Rocks Without Explosives – a Mine Safety Paradigm Shift

This lecture reviews the results of a four-year project sponsored by Natural Resources Canada with support from CANMET Mining, Newmont and the Ministry of Economics and Innovation of Quebec. The project aim was to develop an explosive-free method for hard rock breakage in mines using expansive cement. Phase 1 of 3 was concerned with small-scale laboratory tests for peak expansive pressure measurement in steel cylinders and fracture length estimation in granite blocks. Phase 2 encompassed large-scale tests of one-metre-square panels from concrete and granite subjected to biaxial confinement. Numerical modelling was used extensively to design and analyze the drill hole patterns. In Phase 3, field validation tests were carried out at two underground mines, Hoyle Pond and Éléonore owned by Newmont. They included boulder fragmentation and slashing of drift intersection. Future research focusing on applications for narrow vein mining and boulder fragmentation in subzero temperature will be discussed.

The Art and Science of Rockburst Control with Destress Blasting

One of the most common methods that are practiced today for controlling rockbursts in underground mines is destress blasting. One aspect of this method involves drilling and blasting areas that are highly stressed such as crown pillars and mining to help dissipate high stress and energy accumulation. Another aspect of the method relies on large scale blasting of one or more panels near the active mining area to create a stress shadow around it. While the merits of the destress blasting method are conceptually well appreciated by practitioners, its efficient implementation in the field has been hampered by the diversity of available information and the absence of a dedicated design/analysis method. This has made the destress blasting method more like an art than an engineering science. This paper reviews the background theory, benefits, constitutive modelling, and practice of destress blasting. The evaluation of the destress blasting efficiency is discussed, and future research directions are highlighted.