Time for a Change? the Role of Rockmass Characterization and Discrete Fracture Networks on the Assessment of Caving Rockmasses

ABSTRACT: With the trend for block and panel caving projects being in typically deeper, stronger and more heterogenous rock mass conditions, the need for better rock mass characterization has never been greater so that a reliable design can be developed. However, with many of the worldwide caving operations been carried out in more massive rock masses with relatively few joints being present, there is a requirement to improve rock mass characterization which has historically been focused on joints which are not often present in porphyry deposits at depth, the typical caving host rock masses. Failure to step outside historic characterization approaches has resulted in mis-characterized resources and a significant difference between forecasted and actual caving performance. Increasingly improvements in rock mass characterization methods have benefited from more detailed investigations of veining, their role in rock failure mechanisms, and their integration within Discrete Fracture Network (DFN) models. DFN modelling allows for a more statistical approach to rock fabric description by explicitly building 3D synthetic rock mass descriptions for improved visualization and analysis. The objective of rock mass characterization is to be able to accurately define the nature of the rock mass being excavated in terms of whether it is massive, moderately jointed/veined or highly blocky. This understanding is the basis for better analysis with both empirical design methods and advanced numerical modelling. Collectively, the assessments based on a more robust, statistically significant geomechanical representation of these rock masses provides for improved forecasts of extraction level stability, production ramp-up rates, hangup management requirements need for preconditioning, and ground support.