A methodology for calibrating numerical models with a heterogeneous rockmass

• A case study of a Canadian underground mine is examined in a FLAC3D numerical model.
• The pre-mining stress field is generated using boundary tractions and gradients.
• Readings are compared to site measurements and calculated stresses at two locations.
• A new calibration methodology is developed to determine the required tractions.
• Model expansions, elastoplastic behavior, and shear zones can all be accommodated.

Numerical models are increasingly being used to assess the stability of mine openings, and forming an integral part of operational and safety decisions. A key factor in obtaining realistic model results is the correct simulation of the pre-mining stress regime in a heterogeneous rockmass with complex geometries. When in-situ stress measurement results are available, or if an estimate can be made based on the vertical stress gradient in the region, the model can be calibrated based on these values and relied upon to replicate the rockmass behavior in the field. The calibration of a numerical model with a heterogeneous rockmass cannot be reduced to analytical solutions due to the numerous variables involved, especially under elastoplastic conditions or in the vicinity of geological structures. In this paper, a systematic and iterative calibration methodology is presented – based on two different methods of in-situ stress determination – that uses boundary tractions for a mine-wide numerical model of a deep Canadian mine. The effects of lateral and vertical model dimensions, as well as mesh density, are examined to verify the adaptability of the methodology to these changes under linear elastic conditions. In addition, the model is calibrated under elastoplastic conditions and in the presence of a shear zone. It is shown that regardless of any of the modifications, model calibration can be conducted with the proposed methodology.