Obtaining accurate rock mass strengths requires an understanding of the intact rock and joint properties of each geotechnical unit and the in-situ stress state. To estimate rock mass strengths, Itasca uses the full gamut of engineering approaches, including analytical, empirical, and numerical modeling approaches.
Itasca has also pioneered innovative techniques such as synthetic rock mass (SRM) for primary fragmentation prediction and ReBop for secondary fragmentation prediction. SRM is uniquely capable of explicitly accounting for the impacts of existing fractures (joints or veins), as well as new fracture growth, on fragmentation. In this technique, discrete fracture networks (DFNs) are developed to describe the in-situ fracture network geometry based on available frequency, orientation, and trace length data. The properties of the fractures are established from laboratory testing and/or empirical relations for stiffness and strength (i.e., based on logged and/or mapped roughness, alteration and waviness). Simulated DFNs are then embedded within three-dimensional bonded particle/block models representing simulated intact rock specimens. These samples are strained to simulate the primary fragmentation process as a function of expected underground stresses. Such virtual tests can be done at scales much larger than actual laboratory tests—ranging from meters to hundreds of meters in scale. Virtual lab results are presented in the form of fragment size and volume distribution plots and three-dimensional block models of expected primary fragmentation.