Blast Design – Using Scaled Depth of Burial
CIM Montreal 2015
Mark William Grigons (Suncor Energy Inc.)
There are numerous theories concerning blast design and the mechanisms by which rock fragments under high pressures generated when explosives are detonated in a cylindrical geometry. Specific applications such as crater blasting (cratering) dating back to the 1950’s from work published by Clifford Livingston and further research and case studies conducted by Bauer, Chung, Crosby, Chiappetta, Workman and others; have all established the Scaled Depth of Burial calculation into their methodology, and application. Furthermore; they illustrated how crater theory can be usefully employed by any mine and quarry for optimizing efficiency in controlling airblast (venting), flyrock and oversize a result in energy loss. However blast designs cannot be developed solely on the basis of cratering theory.
Most important perimeters to a blast design is drilling controls, the explosives energy, and energy distribution in the rock mass, the timed and controlled release of energy under confinement, influence in heave and swell of the rock mass above an explosives charge. All of which determines the performance and fragmentation beneath and/or within the stemming confinement region during detonation. This is where the application of crater theory is best described. Continuous research and application of the Scaled Depth of Burial calculation in blast designing investigates closely into the displacement of materials above an explosives charge. Preventing flyrock and capitalize on energy distribution.
Crater theory is the fragmentation process of a single buried charge, and what best illustrates how Scaled Depth of Burial is, and how it can be calculated into the controlled release of energy beneath or through the confinement of the rock mass. Furthermore Scaled Depth of Burial can be an engineering tool for factoring safety, performance, predetermined control of swell and heave to the blasthole collar. Crater theory was typically known for its performance as a single point (spherical) charge; however the emphasis here is primarily made on the top portion of the cylindrical charge which performs like a spherical charge on detonation.
Where conventional rules-of-thumb are used to determine an appropriate stemming height above an explosives charge still may be useful; however the significance of Scaled Depth of Burial can provide a calculable analysis and provide safety factors in the distribution of energy controlled through the confinement above any explosive charge. Specific blast design applications using the Scaled Depth of Burial calculation may include the following: ditching and trenching, oil sands, frost or cap rock, short benches, shallow deck charges or stem charges, bench mining, coal seams and ideal for engineering new blasts in any soft, intermediate to hard geological formation.
This presentation illustrates powerful and practical step by step techniques in using the Scaled Depth of Burial calculation when designing a blast, and the safety factors to observe and monitor in blast designing to prevent wasteful energy loss and dangerous flyrock or over confinement smothering detonation energy creating poor fragmentation and unproductive recovery.
Mots clés :
energy distribution, optimizing efficiency, Preventing flyrock, explosives energy, drilling controls, calculable analysis, factoring safety, performance, predetermined contr, controlled release of energy under confinement