Introduction to Part C: Application to practice
This part introduction presents an overview of the key concepts discussed in the subsequent chapters. The part presents the methods of assessment of rock in order to predict excavation performance. The excavatability of a rock mass is mainly determined by the strength of the rock material and the density and orientation of discontinuities in the rock mass. The part also discusses the example of the tunnel boring machine model of the Norwegian Technology Institute, and presents the example of ripping. Ripping occurs when the cutting tool is loosening the blocks of rock bounded by the discontinuities of the rock mass. J. A. Franklin et al. used joint density and unconfined rock material strength to design an excavatability graph. The Franklin method and the rock mass classification systems used in Engineering Geology site investigation are intended to give an indication of the way a rock can be excavated.