Geology Reference
In-Depth Information
It is dif
cult to de
ne engineering geology as a separate discipline but easier to de
ne the subject areas with
which an engineering geologist needs to be familiar. These include:
1. GEOLOGY
An in-depth knowledge of geology: the nature, formation and structure of soils and rocks. The ability to
interpret the geological history of a site.
2. ENGINEERING GEOLOGY AND HYDROGEOLOGY
Aspects of geology and geological processes that are not normally covered well in an undergraduate geological
degree syllabus need to be learned through advanced study (MSc and continuing education) or during
employment. These include:
-
Methods and techniques for sub-surface investigation.
-
Properties of soil and rock, such as strength, permeability and deformability
-
how to measure these in the
laboratory (material scale) and in the
field and how to apply these at the large scale (mass scale) to geological
models.
-
Methods for soil and rock description and classi
cation for engineering purposes.
-
Weathering processes and the nature of weathered rocks.
-
Quaternary history, deposits and sea level changes.
-
Nature, origins and physical properties of discontinuities.
-
Hydrogeology: in
ltration of water, hydraulic conductivity and controlling factors. Water pressure in the
ground, drainage techniques.
-
Key factors that will affect engineering projects, such as forces and stresses, earthquakes, blast vibrations,
chemical reactions and deterioration.
-
Numerical characterisation, modelling and analysis.
These are dealt with primarily in
Chapters 3
,
4,
5
&
6.
3. GEOMORPHOLOGY
Most engineering projects are constructed close to the land surface and therefore geomorphology is very important.
An engineer might consider a site in an analytical way, for example, using predicted 100-year rainfall and catchment
analysis to predict
flood levels and carrying out stability analysis to determine the hazard from natural slope
landslides. This process can be partially shortcut and certainly enhanced through a proper interpretation of the
relatively recent history of a site, as expressed by its current topography and the distribution of surface materials. For
example, study of river terraces can help determine likely maximum
flood levels and can also give some indication of
earthquake history in active regions such as New Zealand. The recognition of past landslides through air photo
interpretation is a fundamental part of desk study for many hilly sites. This is dealt with in
Chapters 3
and
4.
4. CIVIL ENGINEERING DESIGN AND PRACTICE
An engineering geologist must be familiar with the principles of the design of structures and the options, say for
founding a building or for constructing a tunnel. He/she must be able to work in a team of civil and structural
engineers, providing adequate ground models that can be analysed to predict project performance, and this
requires some considerable knowledge of engineering practice and terminology. The geological ground condi-
tions need to be modelled mechanically and the engineering geologist needs to be aware of how this is done and,
better still, able to do so himself. This is covered mainly in
Chapters 2
and
6.
5. SOIL AND ROCK MECHANICS
Engineering geology requires quanti
cation of geological models. Hoek (1999) described the process as
'
putting
numbers to geology
they do, for
example, in analysing sedimentary processes, in structural geology and in geochronology. However, a geologist
is usually concerned with relatively slow processes and very high stress levels at great depths. The behaviour of
soil and rock in the shorter term (days and months) and at relatively low stresses are the province of soil
mechanics and rock mechanics. Knowledge of the principles and practice of soil and rock mechanics is
important for the engineering geologist. This includes strength, compressibility and permeability at material and
mass scales, the principle of effective stresses, strain-induced changes, critical states and dilation in rock masses.
'
. That is not to say that pure geologists do not take a quantitative approach
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