Engineering Rock Mechanics

(Jacob Rumans) #1
4 Introduction

Figure 1.5 Unlined tunnel excavated by a tunnel boring machine (tunnel face to
left, tunnel wall to right of photograph).

made in rock. Clearly, it is helpful to be able to evaluate the stability of the
excavation-whatever size it may be. This highlights another crucial aspect
which has only really been developed since the 1970s, and that is
understanding the full role of the rock structure, i.e. not only the intact rock
but also the rock fractures and their three-dimensional configuration. In
general, the stability of near surface excavations is governed by the rock
structure, whereas, deeper excavations can be more affected by the intact
rock and pre-existing stresses.
Thus, the rock structure is particularly important in civil engineering and
open-pit mines and so it is necessary to be able to characterize and understand
the mechanics of a discontinuum. This is well illustrated by the two pho-
tographs in Figs 1.7 and 1.8, the first showing how individual rock blocks are
formed and the second showing a large open-pit mine with some instabilities.
In fact, there are numerous applications for rock engineering and three
are illustrated in Figs 1.9-1.11. Some of the most important are dam
abutments and foundations, mining methods (whether as open-pit or as a
whole variety of underground techniques) and now non-precedent
applications for which there is no previous experience to guide us. These
latter projects include geothermal energy, radioactive waste disposal and
the general use of underground space for hosting a miscellany of low- and
high-technology activities, such as domestic refuse treatment and large

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