ABSTRACT
Rock differs from most other engineering materials in that it contains discontinuities of one type or another which render its structure discontinuous. Thus a clear distinction must be made between the intact rock or rock material on the one hand and the rock mass on the other. The intact rock may be considered as a continuum or polycrystalline solid between discontinuities consisting of an aggregate of minerals or grains. The rock mass is the in situ medium comprised of intact rock blocks separated by discontinuities such as joints, bedding planes, folds, sheared zones and faults. The properties of the intact rock are governed by the physical properties of the materials of which it is composed and the manner in which they are bonded to each other. The parameters which may be used in a description of intact rock include petrological name, color, texture, grain size, minor lithological characteristics, degree of weathering or alternation, density, porosity, strength, hardness and deformability. Rock masses are discontinuous and often have heterogeneous and anisotropic properties. Since the behavior of a rock mass is, to a large extent, determined by the type, spacing, orientation and characteristics of the discontinuities present, the parameters used to describe a rock mass include the nature and geometry of discontinuities as well as its overall strength and deformability.
