Page 13 - Rock Mechanics For Underground Mining

Preface to the second edition

Since the publication of the first edition, several developments in rock mechanics have
occurred which justified a comprehensive revision of the text. In the field of solid
mechanics, major advances have been observed in understanding the fundamental
modes of deformation, failure and stability of rock under conditions where rock
stress is high in relation to rock strength. From the point of view of excavation design
practice, a capacity for computational analysis of rock stress and displacement is
more widely distributed at mine sites than at the time of preparing the first edition. In
rock engineering practice, the development and demonstration of large-scale ground
control techniques has resulted in modification of operating conditions, particularly
with respect to maintenance of large stable working spans in open excavations. Each
of these advances has major consequences for rock mechanics practice in mining and
other underground engineering operations.
The advances in solid mechanics and geo-materials science have been dominated
by two developments. First, strain localisation in a frictional, dilatant solid is now
recognised as a source of excavation and mine instability. Second, variations in
displacement-dependent and velocity-dependent frictional resistance to slip are ac-
cepted as controlling mechanisms in stability of sliding of discontinuities. Rockbursts
may involve both strain localisation and joint slip, suggesting mitigation of this per-
vasive mining problem can now be based on principles derived from the governing
mechanics. The revision has resulted in increased attention to rockburst mechanics
and to mine design and operating measures which exploit the state of contemporary
knowledge.
The development and deployment of computational methods for design in rock
is illustrated by the increased consideration in the text of topics such as numerical
methods for support and reinforcement design, and by discussion of several case
studies of numerical simulation of rock response to mining. Other applications of
numerical methods of stress and displacement analysis for mine layout and design
are well established. Nevertheless, simple analytical solutions will continue to be
used in preliminary assessment of design problems and to provide a basis for engi-
neering judgement of mine rock performance. Several important solutions for zone
of influence of excavations have been revised to provide a wider scope for confident
application.
Significant improvements in ground control practice in underground mines are
represented by the engineered use of backfill in deep-level mining and in application
of long, grouted steel tendons or cable bolts in open stoping. In both cases, the
engineering practices are based on analysis of the interaction between the host rock
andthesupportorreinforcementsystem.Fielddemonstrationexerciseswhichvalidate
these ground control methods and the related design procedures provide an assurance
of their technical soundness and practical utility.

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