Geology Reference
In-Depth Information
In the Australian Standard, a material weathering classi
cation is prescribed (but no mass
classi
nition as in
Table C4 (
Geoguide 3) but
using some different terms. DW includes material ranging from the strength of fresh rock to material
that falls apart in water.
cation). The various grades are essentially the same de
TERM
SYMBOL
DESCRIPTION
COMMENTS
Soil developed on extremely
weathered rock; the mass struc-
ture and substance fabric are no
longer evident; there is a large
change in volume but the soil has
not been signi
Same as Geoguide 3.
RESIDUAL
SOIL
RS
cantly
transported.
Rock is weathered to such an
extent that it has soil properties,
i.e. it either disintegrates or it can
be remoulded in water.
However, it retains rock
structure.
Same de
nition as completely
weathered rock (Moye, 1955)
and Geoguide 3.
EXTREMELY
WEATHERED
ROCK
XW
Rock strength usually changed
by weathering. The rock may
be highly discoloured, usually
by iron staining. Porosity may
be increased by leaching, or
may be decreased due to
deposition of weathering
products in pores.
DISTINCTLY
WEATHERED
ROCK
DW
*
SLIGHTLY
WEATHERED
ROCK
Rock is slightly discoloured but
shows little or no change of
strength from fresh rock.
SW
Rock shows no sign of
decomposition or staining
FRESH ROCK
FR
*C
overs highly weathered and moderately weathered classes commonly used internationally. HW and MW
classes may be used if noted in explanatory notes.
practice, the boundary between grades III and IV is often taken as
distinguishing between rock-like and soil-like behaviour for slope
analysis,
able, and is often used in specifying
target depths for piling, so the advantage of grouping them
together is not obvious. The Australian and Hong Kong example
borehole logs presented in Appendix D illustrate the use of mate-
rial weathering grades in practice. Larger-scale mass exposures,
such as those with corestone development, can be described with
reference to the distribution of the various material classi
is readily identi
cation
grades as illustrated in
Figure 3.61.
