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Hereby the dry solids md are determined after drying of
the soil sample at 105 °C. The grain volume is determined
by a Capillarpyknometer. The measurement method of the
Capillarpyknometer is to determine the volume of the solid
with the help of the added water volume. The pyknometer
consists of a volumetric flask with a filling volume that
can exactly be ascertained. The grain volume can be
calculated from the weight of the pyknometer which is to
be filled, the water-filled pyknometer, and the pyknometer
filled with water and a measured sample amount of dried
and crushed soil.
The grain weight γ S of soil describes the weight G
(kN/m 3 ), depending on the volume V K . The grain weight can
be calculated from the grain density with the following
term:
Term 6:
⎡kN
⎤ ⎡ g t ⎤
1,
0 ⋅γ S ⎢ ⎥
= 9,
81 ⋅ ρ
3
S
⎣ ⎦
⎢
bzw.
3
3
m
⎣cm
m ⎥
⎦
In practical calculations the gravitational acceleration
g can approximatively be set at a value of 10. This
results in:
Term 7:
γ
S
⎡kN
⎤
⎢ ⎥
≈ 10 ⋅ ρ
3
⎣m
⎦
⎡ g t
⎢
bzw.
3
⎣cm
m
Table 2:
Weights and densities of various soil groups
Type of soil
high cohasive
soil
low cohasive
soil
non cohasive
soil
S
grain
density
ρ s [g/cm³]
3
⎤
⎥
⎦
grain
weight
γ s [kN/m³]
Dry-weight
γ D [kN/m³]
EDUCATION
The grain density ρ S and grain weight γ S , respectively,
serves as an auxiliary value to determine the porosity, the
water content through immersion weighing and the grain
size composition of a soil sample through sedimentation
analysis.
In case of soil density and weight, (in contrast to grain
density and weight) the volume V is the entire volumes of
the solid substance, the pore fluid and the pore air.
In the following table 2 typical grain densities, grain
weights, as well as other parameters of non-cohesive and
cohesive soils are gathered.
Weight of
wet soil
γ [kN/m³]
Wichte of
waterlogged
soil
γ I [kN/m³]
Pic. 10:
Measuring principle of a
capillary pyknometer [10]
Weight of
soil by uplift
γ [kN/m³]
2,7 - 2,75 27,0 - 27,5 11,0 - 17,0 16,0 - 20,0 17,0 - 21,0 7,0 - 9,0
2,67 26,7 16,0 - 21,0 19,0 - 22,0 20,0 - 23,0 9,0 - 11,0
2,65 26,5 15,0 - 18,0 16,0 - 20,0 19,0 - 22,0 10,0 - 11,0
Issue 04 | 2010 www.advanced-mining.com
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