In the last chapter, some of the idealized models were presented that have been developed to provide a basic grasp of the instability mechanisms associated with slopes and foundations in rock. Although the models are highly simplified, they do assist understanding and indicate the important parameters, together with their sensitivity. When faced with the design and analysis of an actual surface excavation, one has to go beyond these primary models and match the model with the site reality and the nature of the rock.

Thus we should ask what is the exact design objective, what mechanisms are likely to be operating, which data are required as a consequence, and does the model incorporate the discontinuous, inhomogeneous, anisotrop-ic and non-elastic behaviour of the ground, together with factors such as the effects of blasting, rainfall, seismic risk and so on? The approach should therefore be to examine the potential for instability mechanisms and to gradually refine the design and analysis, from an initial skeletal approach through to a comprehensive finely-tuned design. In this book we are discussing principles and hence the techniques which may be applied during the initial approach to all projects. Any further development should be tailored to the rock, site and project circumstances in the knowledge that the initial analyses have been performed thoroughly.