Foundations of engineering geology

Foundations of engineering geology

Civil engineering is an exciting combination of science,
art, professional skill and engineering achievement which
always has to rely on the ground on which its structures
stand. Geology is therefore vital to success in civil
engineering, and this book brings to the reader those
many aspects of the geological sciences specifically
relevant to the profession.
This book is structured primarily for the student of civil
engineering who starts with no knowledge of geology but
is required to understand the ground conditions
and geological processes which, both literally and
metaphori cally, are the foundations of his future
professional activi ties. It also provides an accessible
source of information for the practising civil engineer.
All the material is presented in individual double-page
spreads. Each subject is covered by notes, diagrams,
tables and case histories, all in bite-sized sections instead
of being lost in a long continuous text. This style makes
the information very accessible; the reader can dip in and
find what he needs, and is also visually guided into
relevant associated topics. There is even some intended
repetition of small sections of material which are pertinent
to more than one aspect within the interrelated framework
of a geological understanding.

The contents of the book follow a basic university
course in engineering geology. The freestanding sections
and subsections permit infinite flexibility, so that any
lecturer can use the book as his course text while
tailoring his programme to his own personal style. The
single section summarizing soil strength has been
included for the benefit of geology students who do not
take a comprehensive course in soil mechanics within a

normal civil engineering syllabus.The sectionalized layout makes the information very
accessible, so that the practising engineer will find the
book to be a useful source when he requires a rapid
insight or reminder as he encounters geological problems
with difficult ground. Reference material has therefore
been added to many sections, mainly in tabulated form, to
provide a more complete data bank. The book has been
produced mainly in the inexpensive soft-bound format in
the hope that it will reach as large a market as possible.
The mass of data condensed into these pages has
been drawn from an enormous variety of sources. The
book is unashamedly a derived text, relying heavily on the
world-wide records of engineering geology. Material has
been accumulated over many years in a lecturing role. A
few concepts and case histories do derive from the
author’s personal research; but for the dominant part,
there is a debt of gratitude acknowledged to the innumer -
able geologists and civil engineers who have described
and communicated their own experiences and research.
All the figures have been newly drawn, and many are
derived from a combination of disparate sources. The
photographs are by the author.

Earth is an active planet in a constant state of change.
Geological processes continually modify the Earth’s
surface, destroy old rocks, create new rocks and add to
the complexity of ground conditions.
Cycle of geology encompasses all major processes,
which are cyclic, or they would grind to an inevitable halt.
Land: mainly erosion and rock destruction.
Sea: mainly deposition, forming new sediments.
Underground: new rocks created and deformed.
Earth movements are vital to the cycle; without them the
land would be eroded down to just below sea level.
Plate tectonics provide the mechanism for nearly all
earth movements (section 09). The hot interior of the
Earth is the ultimate energy source, which drives all
geological processes.
Geological time is an important concept. Earth is
4000M years old and has evolved continuously towards
its present form.

Most rocks encountered by engineers are 10–500M
years old. They have been displaced and deformed over
time, and some are then exposed at the surface by
erosional removal of rocks that once lay above them.
Underground structures and the ground surface have
evolved steadily through geological time.
Most surface landforms visible today have been
carved out by erosion within the last few million years,
while older landforms have been destroyed.
This time difference is important: the origin of the rocks
at the surface may bear no relationship to the present
environment. The classic example is Mt Everest, whose
summit is limestone, formed in a sea 300M years ago.
Geological time is difficult to comprehend but it must be
accepted as the time gaps account for many of the

contrasts in ground conditions.

Natural ground materials, rocks and soils, cover a great
range of strengths: granite is about 4000 times stronger
than peat soil.
Some variations in rock strength are summarized by
contrasting strong and weak rocks in the table.
Assessment of ground conditions must distinguish:
• Intact rock – strength of an unfractured, small block;
refer to UCS.
• Rock mass – properties of a large mass of fractured
rock in the ground; refer to rock mass
classes (section 25).
Note – a strong rock may contain so many fractures in a
hillside that the rock mass is weak and unstable.
Ground conditions also vary greatly due to purely local
features such as underground cavities, inclined shear

surfaces and artificial disturbance.


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