The first and most important phase of any numerical modelling calibration is the development of a ‘ground behaviour model’ (a term which describes the compilation of all available site geotechnical data). With such a model on hand, the practitioner tasked with numerical simulation is more likely to understand, or at least conceptualize, the fundamental mechanics of the problem prior to developing a simulation.  A ground behaviour model includes:

  • Raw geotechnical data (geotechnical mapping, geotechnical core logging, laboratory results)
  • Domained rock mass conditions (rock mass classification and parameterization)
  • Geology
  • As-built excavation and design geometries
  • Instrumentation data
  • Ground support performance
  • Damage and mechanism mapping
  • Falls of ground or failures
  • Water

The second step in numerical modelling calibration is categorizing ground response.  Ground response categorization describes the significance of ground reaction, with consideration for hazard and risk.  This process is often site-specific and is closely tied to the available means of risk mitigation (see examples of ground response categorization in the figure below).  The concept here is that a particular ground reaction can be attributed to a specific stress-strain path (within some tolerance).  Therefore, when it comes to forward simulation, practitioners can resolve that a reasonably similar stress-strain path is likely to contribute to the same category of ground reaction.

Figure:  Categorization of ground response (source – modified after Kalenchuk, K,  Crockford, A, Hume, C, Milner, N, Watson, J, 2014. Application of Numerical Modelling to Predict Seismic Probability and Mitigate Associated Risks during the Craig Pillar Extraction at Morrison Mine, KGHM International.  48th US Rock Mechanics/Geomechanics Symposium. Minneapolis).