392 Design and analysis of underground excavations
sis. Moreover, there are also codes available for three-dimensional analysis
of fluid flow through fracture networks. In addition to these off-the-shelf
codes, there are manifold proprietary programs in which, for example,
hybrid discrete element and finite element analyses are combined with the
analysis of fluid flow.
In the early days of these programs, the computing was often difficult
for the average user. We are now experiencing a major development in the
ease of use of these methods through the use of improved graphical
interfaces, so there is now every reason to apply such programs to all
projects. However, it is of paramount importance to be certain that the rock
mechanics and rock engineering principles are fully understood, and that
the output from the computer programs is in accordance with these
principles.
The nature of a complete rock engineering project is that it will contain
components of many different kinds which need to be integrated. Our final
remarks consider integrated design procedures and how they have evolved
over the years.
20.3 Integrated design procedures
There is currently no overall standard procedure for the design and
construction of a rock engineering project. In this book, we have presented
a range of principles relating to engineering rock mechanics. The rock may
well be inhomogeneous and anisotropic, in short, not always ideally suited
for analysis. Indeed, we may well not have sufficient information about the
site geology itself. A variety of contributing factors may influence our
decisions: these can be in the areas of finance, environment, management
and so on. Thus, we have a suite of well-understood supporting modules
for the rock engineering (6. Hudson, 19!23), but not a universally utilized
overall design methodology.
Techniques are presented in the books by Hoek and Brown (1980),
Franklin and Dusseault (1989) and Bieniawski (1989). The Hoek and Brown
methodology is concerned with identifymg whether instability is likely to
be the result of rock structure, rock stress, weathering or time. The Franklin
methodology provides an extensive introduction to all the techniques
available. The Bieniawski approach is more in line with classic management
type charts. The rock engineering systems approach introduced in Chap-
ter 14 enables the structure of the system to be generated and its operation
to be studied in terms of critical mechanisms and hazards (Hudson and
Jiao, 1996). It must be borne in mind that each of these methods has
different advantages and values, depending on the engineering context
and objectives.
Thus, the engineer should make an informed choice as to which, if any,
of these methodologies is appropriate to their circumstances. In order to
make an informed choice, the engineer must be fully conversant with the
principles of engineering rock mechanics-which is what has been present-
ed in this book.