Elastic Versus Inelastic Numerical Modelling of Deep and Highly Stressed Mining Fronts

With the current trend of exploiting mines at increasing depths comes the challenge of managing increasingly high stress conditions. One tool at the disposal of mine engineers and designers is the numerical simulation of the stresses and deformations likely to be encountered ahead of the mining fronts for various mining scenarios. Although the benefits of numerical modelling are by now well accepted throughout the industry, the applicability of the various types of numerical modelling approaches is not always well understood and still the subject of much debate. This paper endeavours to explain the basic differences between the elastic and inelastic approaches, as well as provide practical guidelines concerning which one to use for various sets of circumstances. Case studies of high stress situations are provided that show where the simpler elastic approach was adequate, and where implementing an inelastic approach was unavoidable. Some insight is also provided into the type of practical information that can be extracted from advanced failure analyses (the exclusive domain of inelastic techniques), such as determining the degree of failure of a rock mass by examining the stress state of its failed zones, which indicates their position along the strain-softening post-peak response typical of hard rock masses.