Defining in-situ block size.

CIM Bulletin, Vol. 91, No. 1020, 1998

J. Hadjigeorgiou, M. Grenon, Department of Mining & Metallurgy, Université Laval, Quebec City, Quebec
J.F. Lessard, Mine Louvicourt, Aur Resources, Val d'Or, Quebec

The presence, size, orientation, nature, and persistence of geological discontinuities dictate the behaviour of a rock mass. Block size, which is defined by discontinuity spacing, by the number of joint sets, and by the persistence of the discontinuities delineating potential blocks is an important indicator of the degree of fracturing of a rock mass. Consequently, block size is represented either explicitly or implicitly in all rock mass classification systems employed for analysis and design of surface and underground mining structures. In-situ block size distributions may provide a better means to describe the structural complexity of a rock mass. These are the distributions that would be derived if the in-situ rock mass was separated into its constitutive blocks, delineated by existing discontinuities, and each block measured. This paper presents the results of a field campaign at Louvicourt Mine aiming to characterize the rock mass using different methods for determining block size and block size distributions.

Keywords: Rock mechanics, Rock mass characterization, Block size.