Controlled fragmentation and contours in rock blasting theoretical and technical approaches

Abstract: The Swedish mining and construction industries have a large interest in improving blasting technology, in milling concerning rock fragmentation by blasting (especially underground in large diameter hole blasting, > 100 mm) and in construction and mining concerning controlled and safe contours in blasted tunnels. This doctoral thesis deals with these matters and includes a licentiate thesis (published in 1970) and five papers A-E included in the doctoral thesis and published during 1983 to 1992. The licentiate thesis (in Swedish) presents the development of a method to determine the ore content in an LHD-bucket after loading iron ore in the mine. The method is based on measuring the bulk density of the ore-waste mixture. In order to investigate the accuracy of the method a theoretical model was established, and verified by model-scale blasting tests and research concerning fragmentation and swelling of blasted ore under varying technical and environmental conditions. Paper A describes a part of the licentiate thesis, the development and choice of a suitable model material for the blasting tests. Controlled Contour Blasting Technique (Paper B) especially in tunnelling, needs improvement in bad rock. Literature studies and model and full-scale tests were the base for the evaluation of the existing and proposed contour blasting methods. Controlled Rock Fragmentation (Paper C, D, and E) is an important goal, especially in large hole diameter blasting. New design formulas were therefore developed for mean fragment size, rock fragment size distribution, etc. in connection with technical parameters such as burden or specific charge, spacing and rock impedance. The formulas are based on literature studies and model and flill-scale tests. A new relation between the burden and blasthole diameter was derived from statistical analysis of data from one hundred surface and underground mines. The relation is different for surface and underground mines.