Geology Reference
In-Depth Information
5. grain size
6.
rock name (in capitals, e.g. GRANITE)
B) General information
1. additional information and minor constituents
2. geological formation
C) Mass characteristics
1.
state of weathering
2.
discontinuities
BS 5930 (BSI, 1999) should be consulted for all terms and de
nitions
as used in British practice. A detailed commentary is given by Norbury
(2010). Other countries have their own terms and practice guidance, so
the engineering geologist needs to be aware of local usage wherever he
is working.
soil description and
Table C3
presents common terminology for
describing the strength and compactness of detrital sediments.
Such terms and index tests may not be appropriate or adequate
for describing and classifying soil-like materials derived by
in situ
weathering.
C.5 Rock description and classi
cation
For rock, key issues are intact rock strength, nature of discontinuities,
weathering and rock mass classi
cation.
Intact strength of rock material is very different from mass
strength, as addressed in
Chapter 5,
and usually to a greater
degree than for soils, albeit that soil also contains joints, shear
planes and general
fissures and fractures that
in
uence mass
behaviour.
Strength can be estimated quite readily in absolute terms (MPa)
by simply hitting it with a hammer or trying to break it by hand
and quite often no further testing will be required (see
Box 5-1).
Despite this, the geotechnical community has been inconsistent in its
terminology for 50 years. Some of the de
nitions used worldwide
