ABSTRACT
Bieniawski’s Simplicity Principle corresponds with “Design or borrow the simplest model that will allow the important mechanisms to occur. Excavation involves unloading of the rock, and behaviour is commonly linear, hence value in elastic modelling. Therefore single values of E and v in analyses, as commonly practised, could be misleading Synthetic rock mass analyses illustrate different strengths and moduli in different directions. Many publications that appear in the literature assume the mode of behaviour, and modify rock mass properties until an apparent match with observed behaviour is obtained; the assumption is then made that the modelled rock mass properties are “correct”, and applicable for analysis of further situations. Numerical models must take into account the mechanisms of rock fracture and failure. Fractures may initiate due to one criterion, propagate due to the same or other criteria, and failure may develop due to yet other criteria, including structural criteria such as beam bending and buckling, plate buckling etc.
