Specific Gravity is the ratio of the density of a soil to the density of water.
Where:
SG = Specific Gravity (dimensionless)
ρs = bulk density of soil (kg/m3 or lb/ft3)
ρw = bulk density of water (kg/m3 or lb/ft3)
= 1000 kg/m3 (62.4 lb/ft3)
Specific Gravity of Various Substances
| Substance | Specific Gravity |
|---|---|
| Water | 1.0 |
| Organic Soils | 2.5 |
| Most soils | 2.65 – 2.70 |
| Clay | 2.9 |
| Iron | 7.9 |
| Copper | 9.0 |
| Gold | 19.3 |
Relative Density
Relative Density is related to Specific Gravity in that it compares the density of a substance to a certain reference density rather than that of water.
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