Design of
20 underground
excavations
20.1 The project objective
The purpose of the engineered structure will influence its design. For
example, the stabilization measures required for an excavation such as
that illustrated in Fig. 20.1 will depend on whether it is to be a permanent
structure for a civil engineering project or a temporary structure for a
mine. In civil, mining and petroleum engineering, there will be different
constraints on the tolerable disturbance caused by excavation, on the
rock displacements, on the type of instability that can be allowed to
occur, on the type of support that could be installed, etc.
We have to consider what types of instability might be expected.
Will it be instability of rock blocks defined by pre-existing fractures,
r
Figure 20.1 Construction of an underground excavation for a hydro-electric scheme.