Characterisation of jointed rock mass

In this introductory Chapter, a brief description of the rock types and properties, and joint characteristics is given. Various attempts have been made in the past to classify rock mass for important engineering applications underground and on the surface, such as design of mines, highway tunnels, slopes, dam foundations and nuclear waste storage plants. Classification of rocks can be made based on their mineral composition and their origin or types for engineering applications ( Fig. 1.1 ). The geological classification provides mineralogical and chemical data, but it does not directly provide stress-strain characteristics of rocks, which are the most relevant in engineering applications. The existing rocks may be subjected to high pressure and temperature changes resulting in the metamorphic alteration of properties, structurally, mineralogically and texturally. Depending on the geological origin, i.e. stages of weathering, transportation, consolidation and alteration ( Tucker, 1993 ), rocks are usually classified into three major groups, (a) igneous (b) sedimentary and (c) metamorphic rocks. Figure 1.2 shows the common rock types, which come under these principal categories. A simplified geological process is shown in Fig. 1.3 .