Geology Reference
In-Depth Information
Fookes et al. (2000) encourage a
whereby
any site is assessed with regard to its full geological history. That
history includes original formation of the soils or rock underlying the
site, tectonic events, weathering, erosion, deposition of any overlying
super
'
total geological approach
'
cial deposits, geomorphological development and anthropo-
genic in
s
surface to form the landscape and the extensive time involved are
almost inconceivable but must be considered when interpreting the
geology at any site.
Total geological analysis should allow the distribution and nature of
the various strata at the site and other features, such as hydrogeologi-
cal conditions, to be explained. The assessment should be based on the
extensive literature on geological and geomorphological processes,
which comprises the toolbox for interpreting the conditions that are
encountered at any site. Useful sources of information on geology
focused on civil engineering application are Blyth & de Freitas
(1984) and Goodman (1993) but often, to understand what is happen-
ing at a site, one has to refer to more fundamental geological literature.
This chapter introduces aspects of geology that are relevant to engi-
neering design and performance. It commences by considering the
three basic rock types
uences. The changes that have taken place at the Earth
'
-
focusing on their typical characteristics and associations that may be
of particular importance to engineering. The next section introduces
rock structures, particularly the origins and characteristics of disconti-
nuities that tend to control rock mass properties. Towards the end of
the chapter, guidance is given on developing ground models for a site.
-
igneous, sedimentary and metamorphic
3.3.2 The need for simpli
cation and classi
cation
As discussed in
Chapter 4,
simpli
ed approaches are generally adopted
for the description and classi
cation of soils and rocks for engineering
purposes, largely because geological detail is often irrelevant. This espe-
cially applies to logging soil and rock encountered in boreholes.
Nevertheless, the engineering geologist needs to be alert to situations
and cases where geological detail might be important to explain
the geological situation or because particular characteristics have some
special signi
'
s experience, whilst many sites are
described and characterised quite adequately using shorthand terms and
classi
cance. In the author
cations, occasionally one meets situations where to understand
what is happening, to an adequate level for an engineering project,
intensive study is necessary into geological minutiae, including chemical
analysis, thin section examination and even radiometric dating.
