Rock as an engineering material 13the properties of the material, the pre-existing stress state in the ground
(which will be disturbed by engineering) and consider these in relation
to our engineering objective. In civil engineering, the main objective is to
create a structure by removing the rock. In mining engineering, it is to
obtain the material being removed. A primary information base for these
activities is a knowledge of the geological strata, any alteration to the
rock material, the presence of large- and small-scale faulting and jointing
in the rock, and indeed any geological parameter that is relevant to
the engineering. Clearly, the rock type, the rock structure, any alteration
to the rock, the in situ stress state and hydrogeological regime will be
important for all engineering. There are, however, many other aspects
of the geological setting which could be of major, if not dominant,
significance in the engineering design, construction and subsequent
performance. Examples of these are the presence of large natural caverns
in karstic regions, the presence of buried valleys encountered during
tunnelling, wash-outs in coal seams during mining and the presence of
major horizontal fracture zones in granitic masses for radioactive waste
disposal.
Figure 2.3 Zone of highly fractured rock.