title of the thesis - Department of Geology - Queen's University

(Cundall and Hart, 1992). This allows for the behaviour of the medium as well as the
discontinuities to be modelled. Like Phase 2 , unbalanced forces must be reduced for the model to
reach equilibrium. In this study, rock mass and fault behaviour is represented by a Mohr-
Coulomb constitutive model. Since the Creighton Deep is pervasively faulted, discontinuum
models were used in preference to continuum models and are discussed in this chapter. A
discussion of Phase 2 models can be found in Appendix D.
4.3 Model Input Parameters
Pre-mining stress and model geometry are the main factors that influence the elastic model
response. In plastic models, this and rock strength are an integral part of the rock mass response.
Accurate geometry, stresses and strength parameters are thus required for models. The
determination of these parameters is outlined in this section.
4.3.1 Elastic and Plastic Models
Both elastic and plastic models were developed for the 7400 Level. Elastic models have a linear
response to stress such that deformation is recoverable (Fig. 4.2). Beyond the elastic limit, plastic
models cannot accommodate additional stress. At this point, tractions are reduced until the rock
mass responds by deforming in a non-recoverable manner (yields) and stress is transferred to
surrounding rock (Duncan Fama, 1993; Falmagne, 2001, Wiles, 2006). This behaviour cannot be
simulated using elastic models and thus elasto-plastic models are required. In such models, this
behaviour is achieved through rock mass yielding or slip on faults, if they are present. In the
numerical modeling packages, when stress within an element exceeds the failure criteria, the
element yields and stress is transferred to surrounding elements (Duncan Fama, 1993; Wiles,
2006).
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