Geology Reference
In-Depth Information
5
Tilbury
Älvängen
St Andrew Bay
Oslofjord
A-33
A-31
B-87
C-18
G. of Mexico
S. Joaquin
Ocean
cores
Gosport
Milazzo
Pisa
Kambara
80
4
Avonmouth
Darammen
Baku
Po Valley
Grangemouth
Drammen
75
3
Detroit
%
70
2
60
50
1
Approx 100 mm
below sea bed
40
20
0
Depth
3
10
100
300
1,000
3,000
m
30
ed
from Skempton, 1970).
overconsolidated. In the case of sand, the history of burial compaction
can result in an extremely dense arrangement of the sand particles that
cannot be replicated in the laboratory. Such locked sands, with grains
exhibiting some interpenetration and authigenic overgrowths, not sur-
prisingly, have high frictional resistance and dilate strongly under shear
(Dusseault &Morgenstern, 1979).
5.3.5.3 Fractures
Natural fractures occur in most rocks close to the Earth
ssurfaceandin
many soils once they begin to go through the processes of burial and
lithi
'
cation.
Figure 5.10
shows a quarry face where discontinuities dom-
inate mass geotechnical parameters such as deformability and permeabil-
ity. Vertical joints in relatively young glacial till are shown in
Figure 5.11.
Fractures will often dominate
flow through the mass, as well as mass
deformability and strength. They need special consideration and char-
acterisation, as addressed in
Chapters 3 a
nd
4 a
nd discussed later.
uid
Many soils such as glacial boulder clay and colluvium comprise a
mixture of
finer soil and large clasts of rock, and these need special
