Page 197 - Geotechnical Engineering Soil and Foundation Principles and Practice
P. 197
Soil Density and Unit Weight
192 Geotechnical Engineering
The volume of air equals the total volume minus the volumes of water and
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solids: 442 – 215 – 110 ¼ 117 cm .
The volume of voids equals the volume of water plus the volume of air:
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110 þ 117 ¼ 227 cm .
After the block diagram is completed it is a simple matter to calculate the required
quantities:
(a) w ¼ 100 110/580 ¼ 19.0%.
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(b)
w ¼ 690/442 ¼ 1.56 g/cm ;or 62.4 ¼ 97.4 lb/ft .
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(c)
d ¼ 580/442 ¼ 1.31 g/cm ;or 62.4 ¼ 81.9 lb/ft .
(d) e ¼ 227/215 ¼ 1.06.
(e) n ¼ 100 (227/442) ¼ 51.3%.
(f) For saturated unit weight the air voids are replaced by water that has a weight
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of 117 1.0 ¼ 117. Then
sat ¼ (690 þ 117)/442 ¼ 1.83 g/cm or 113.9 lb/ft .
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(g)
sub ¼ 1.83 – 1.0 ¼ 0.83 g/m , or 113.9 – 62.4 ¼ 51.5 lb/ft .
Problems
9.1. Convert the following wet densities and moisture contents to dry densities:
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(a) 18.85 kN/m , 15%.
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(b) 117 1b/ft , 17%.
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(c) 21.21 kN/m , 21%.
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(d) 15.87 kN/m , 5%.
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(e) 120 lb/ft , 12%.
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(f) 14.14 kN/m , 102%.
9.2. If 2.70, find the void ratio for each of the above.
9.3. Calculate the saturated and the submerged unit weights of each of the above.
9.4. An undisturbed sample of soil weighing 49.95 N (11.23 lb) is coated with
paraffin and suspended by a string in water to give a submerged weight of
24.42 N (5.49 lb). If the sample contains 13.4% moisture and has a true
specific gravity of 2.65, calculate the following properties: (a) wet density,
(b) dry density, (c) void ratio, (d) porosity, (e) saturation, (f) percent water
voids, (g) percent air voids, (h) percent solids.
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9.5. If 171,900 m (224,800 yd ) of soil are removed from a highway cut in which
the void ratio is 1.22, how many cubic meters (yards) of fill having a void
ratio of 0.78 could be constructed?
9.6. If the true specific gravity of the soil in Problem 9.5 is 2.70 and it contains
10% moisture, how many meganewtons (tons) of soil will have to be moved?
How many meganewtons (tons) of dry soil will there be? How many
meganewtons (tons) of water will there be in the soil?
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