Geoscience Reference
In-Depth Information
the geological strength description of clays and silts (tested by fingers), and sands
and rocks (tested by hand or hammer).
TABLE 2.1 GEOLOGICAL STRENGTH
clay and silt
very
sof
very
stiff
soft
firm
stiff
hard
undrained shear strength clays (kN/m 2 )
10 20 40 60 80 100
squeeze mould indent tick
sand and rock
very
weak
very
strong
extremely
strong
weak
stiff
strong
unconfined compressive strength (MN/m 2 )
0.5 1 5 10 50 100 200
crumble crush scratch peel notch chip
B GRAVIMETRIC - VOLUMETRIC DATA
Soil is a multiphase system, containing a volume V s of solids (grains), a volume
V w of fluid (water) and a volume V a of gas (air), with a total volume V . The fluid
and/or gas fills the pore space volume V p in between a complex structure of grains
(grain skeleton). In Table 2.2 common symbols used to define the phase content
are compiled.
Many soils consist of a mixture of sand, silt, clay and organic material. The
organic material typically has a specific gravity of 1.4. In peat soils the organic
content is so high that the specific solid gravity G s is noticeably influenced
1/G s
OC/1.4 + (1-OC)/2.65
(2.1)
where OC is the mass proportion of organic material to total solids. OC varies
from 1 in pure peat to approximately 0.2 in very clayey peat, with G s increasing
correspondingly. For soft organic soils G s can not be simply assumed but must be
determined in the laboratory.
TABLE 2.2a
GRAVIMETRIC / VOLUMETRIC DATA
n
porosity
= V p /V
= e /(1
e )
e
voids ratio
= V p /V s
= n /(1 n )
v
specific volume
= 1
e
= 1/(1 n )
s
saturation degree
= V w /V p
w
water content
= W w /W s
= se/G s
unit weight of water
= W w /V w
w
= W s /V s
s
unit weight of solid
G s
specific (solid) gravity
= s / w
wet unit weight (solids plus water)
= W/V
= (1
w)G s w /(1
e )
dry unit weight (solids)
= W s /V
d
= /(1 w)
'
submerged unit weight (solids)
=
w
D r
relative density
= ( e max - e ) / ( e max - e min )
Search WWH ::




Custom Search