Geology Reference
In-Depth Information
description and classi
cation for
engineering purposes
C.1 Warning
It would be very nice to set out here a guide to soil and rock description
that could be applied worldwide. Unfortunately, that is not possible
-
different countries and different international societies have their own
terminologies and things are getting worse
not better. In this appen-
dix, I try to set out what is common practice or at least widely used.
Where this is not possible, I set out some of the disagreements and in
some instances argue the case.
Engineering geologists and geotechnical engineers, working in any
country, need to comply with local regulations, and this will often
apply to standards for soil and rock description. This can be dif
-
cult
and many will feel uncomfortable at using strange and perhaps poorly
de
ca-
tions and to give actual data instead. We might disagree internationally
over what
ned terms. One option, sometimes, is to avoid the use of classi
rock means but UCS = 45MPa
is clear and a metre is a metre everywhere. That said, there are different
testing methods and different capabilities re testing so even
'
strong
'
or
'
highly weathered
'
'
absolute
'
numbers must be treated with some caution.
Standardisation of soil and rock description has been an aspiration of
many individuals and working groups over the last 50 years. A brief
review is given below.
Much of the soil description and classi
cation terminology has been
fairly standardised since the days of Terzhagi and Casagrande (1948).
Deere (1968) made various proposals re rock strength classi
cation
and discontinuity spacing and introduced the Rock Quality
Designation (RQD), and much of the terminology he recommended
continues to be used in some parts of the world, not least the USA
(Hunt, 2005). One of the earliest attempts to provide fairly compre-
hensive guidance for logging rotary core through rock was the
Geological Society Engineering Group Working Party Report (Anon,
1970). That report and another on maps and plans (Anon, 1972) set
many standards
that were then followed, particularly in the
