Geology Reference
In-Depth Information
(2008) for further discussion.
The Eurocode 7 scheme is the 1978 ISRM scheme but with different grade numbers. This type of
scheme can be applied as descriptive shorthand in areas where weathering is a relatively minor
consideration, as illustrated for the greywacke and schists of southern Portugal (Pinho
et al
., 2006)
and can also be used for more deeply weathered heterogeneous zones. It is dif
cult, however, to log
core using this scheme and this causes dif
culties for many workers. Deere & Deere (1988) rede
ne
'
sound and hard
'
rock for RQD as fresh or slightly weathered (ISRM); if the rock core is
'
moderately
weathered
, they say that RQD should be annotated RQD*. This overlooks the dilemma for a logger
that grade III (ISRM, 1978) can include up to 50%
'
'
soil
'
by de
nition.
ISRM (1978)
EUROCODE 7
TERM
DESCRIPTION
DESCRIPTION
I
No visible sign of rock
material weathering; perhaps
slight discolouration on major
discontinuity surfaces.
0
No visible sign of rock
material weathering; perhaps
slight discolouration on major
discontinuity surfaces.
FRESH
(100% ROCK)
II
Discolouration indicates
weathering of rock material
and discontinuity surfaces. All
the rock material may be dis-
coloured by weathering and
may be somewhat weaker than
its fresh condition.
1
Discolouration indicates
weathering of rock material
and discontinuity surfaces.
SLIGHTLY
WEATHERED
(100% ROCK)
III
Less than half of the rock
material is decomposed and/or
disintegrated to a soil. Fresh or
discoloured rock is present
either as a discontinuous fra-
mework or as corestones.
2
Less than half of the rock
material is decomposed or
disintegrated. Fresh or disco-
loured rock is present, either as
a continuous framework or as
corestones.
MODERATELY
WEATHERED(>50%
ROCK)
IV
More than a half of the rock
material is decomposed and/or
disintegrated to a soil. Fresh or
discoloured rock is present
either as a discontinuous fra-
mework or as corestones.
3
More than half of the rock
material is decomposed or
disintegrated. Fresh or
discoloured rock is present,
either as a discontinuous
framework or as corestones.
HIGHLY
WEATHERED
(<50% ROCK)
V
All rock material is decom-
posed and/or disintegrated to
soil. The original mass struc-
ture is still largely intact.
4
All rockmaterial is decomposed
and/ordisintegratedtosoil.The
original mass structure is still
largely intact.
COMPLETELY
WEATHERED(100%
SOIL)
VI
All rock material is converted
to soil. The mass structure and
material fabric are destroyed.
There is a large change in
volume, but the soil has not
been signi
5
All rock material is converted
to soil. The mass structure and
material fabric are destroyed.
There is a large change in
volume, but the soil has not
been signi
RESIDUAL SOIL
(100% SOIL)
cantly transported.
cantly transported.
