Engineering Rock Mechanics

Questions and answers: introduction 5

slip on the pre-existing fractures? Is the stiffness of the concrete support

a significant parameter in these deliberations? If the rock mass is to be

reinforced with rockbolts, where should these be installed? How many

rockbolts should there be? At what orientation should they be installed?

All these issues are highlighted by the photograph in Fig. 1.2.

CHILE - Continuous, Homogeneous, Isotropic and Linearly Elastic;

DIANE - Discontinuous, Inhomogeneous, Anisotropic and Not-Elastic.

These refer to two ways of thinking about and modelling the rock mass.
In the CHILE case, we assume an ideal type of material which is not
fractured, or if it is fractured the fracturing can be incorporated in the
elastic continuum properties. In the DIANE case, the nature of the real
rock mass is recognized and we model accordingly, still often making
gross approximations. Rock mechanics started with the CHILE approach
and has now developed techniques to enable the DIANE approach to
be implemented. It is evident from Fig. 1.2 that a DIANE approach is
essential for this problem, using information about the orientation and
strength of the rock fractures. However, both approaches have their
advantages and disadvantages, and the wise rock engineer will utilize
each to maximal advantage according to the circumstances.
Modelling for rock mechanics and rock engineering should be based
on ensuring that the relevant mechanisms and the governing parameters
relating to the problem in hand have been identified. Then, the choice of
modelling technique is based on the information required, e.g. ensuring
an adequate foundation as illustrated in Fig. 1.2.
Accordingly, and to enhance an engineer’s skills, the question sets in
Chapters 1-13 are designed to improve familiarity with the main rock
mechanics topics and the techniques associated with the topics, such as
stress analysis and hemispherical projection methods. In Chapter 14,
we emphasize the importance of considering the ’rock mass-engineering
structure’ as a complete system. Finally, in Chapters 15-20, the question
sets are related to specific engineering activities and design requirements.
You can read the question and answer text directly in each of the
chapters, as in Section 1.2 following, or you can attempt the ques-
tions first without seeing the answers, as in Question Set 1 in Part B.
Whichever method you choose for reading the book, we recommend
that you read the introductory text for each chapter topic before tackling
the questions.

Above the Frontispiece photograph, there are two acronyms:

1.2 Questions and answers: introduction

In this introductory chapter, there are five questions concerned with the

nature of engineering rock mechanics. In all subsequent chapters there

are ten questions.

Ql.1 Define the following terms:

rock mechanics;

0 engineering rock mechanics;