Understanding jointed rock mass behaviour using a ubiquitous joint approach

This paper outlines a 'ubiquitous joint' method of manipulating linear elastic numerical modelling data from mining case studies. It uses information, obtained from underground observations, geomechanical mapping, and microseismic monitoring, to identify the critical slip angle, slip potential and slip direction of pre-existing planes of weakness in anisotropic jointed rock masses. The results are visualised by means of two- and three- dimensional tools, and a stereographic stress analysis software package. The conventional theory of a single plane of weakness is used to superimpose the effects of individual joint sets, to identify orientations with high potential for frictional sliding. The application of the methodology and software are demonstrated in four case studies. These include: (1) the analysis for stability of the back of a longhole stope topsill; and (2) a horizontal tunnel being driven up-dig against a continuous and moderately spaced joint set. The authors conclude that their approach provides an approximate method for handling several problems where it would be very laborious to use a detailed model on a mine-wide scale. It cannot be used to simulate major structures like faults or dykes, or to describe major stress redistribution processes.