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- Terms and Definitions in Soil Engineering
- Volumetric Relationships of Soil
- 1. Void Ratio
- 2. Porosity
- 3. Degree of saturation
- 4. Percentage air voids
- 5. Air content
- 6. Water content
- Volume Mass Relationship of Soils
- 7. Bulk Mass Density of Soil
- 8. Dry Mass Density
- 9. Saturated Mass Density
- 10. Submerged Mass Density
- 11. Mass Density of Solids
- Volume-Weight Relationships of Soils
- 12. Specific Gravity of Solids
- Basic Soil Relationships
Terms and Definitions in Soil EngineeringVarious definitions of terms used in Geotechnical Soil Engineering are presented.
Volumetric Relationships of Soil
1. Void RatioVoid ratio is the volume of voids to the volume of solids. It is denoted by ‘e’.
e=Vv/VsIt is expressed as a decimal.
2. PorosityIt is defined as the ratio of volume of voids to the total volume. It is denoted by ‘n’.
n=Vv/VIt is generally expressed as a percentage
1/n= 1+ (1/e) = (1+e)/e
n=e/ (1+e) --> (a)
1/e= (1/n)-1= (1-n)/n
e=n/ (1-n) --> (b)In equations (a) and (b), the porosity should be expressed as a ratio and not percentage.
3. Degree of saturationThe degree of saturation is the ratio of the volume of water to the volume of voids. It is denoted by ‘S’.
S=Vw/VvThe degree of saturation generally expressed as a percentage. It is equal to zero when the soil is absolutely dry and 100% when the soil is fully saturated.
4. Percentage air voidsIt is the ratio of volume of air to the total volume.
na= Va/VIt is also expressed as a percentage.
5. Air contentAir content is defined as the ratio of the volume of air to the volume of voids
6. Water contentThe water content (w) is defined as the ratio of the mass of water to the mass of solids
w= Mw/MsIt is also known as the moisture content (m). It is expressed as a percentage but used as a decimal in computation.
Volume Mass Relationship of Soils
7. Bulk Mass Density of SoilThe bulk mass density (?) is defined as the total mass (M) per unit volume (V)
8. Dry Mass DensityThe dry mass density (?d) is defined as the mass of solids per unit total volume
9. Saturated Mass DensityThe saturated mass density (?sat) is the bulk density of the soil when it is fully saturated
10. Submerged Mass DensityWhen the soil exists below water, it is in a submerged condition. The submerged mass density (?') of the soil is defined as the submerged mass per unit total volume.
11. Mass Density of SolidsThe mass density of solids (?s) is equal to the ratio of the mass of solids to the volume of solids ?s=Ms/Vs
Volume-Weight Relationships of Soils
- BULK UNIT WEIGHT (?)= W/V
- DRY UNIT WEIGHT (?d) = Ws/V
- SATURATED UNIT WEIGHT (?sat) = Wsat/V
- SUBMERGED UNIT WEIGHT (?sub or ?') = Wsub/V
- UNIT WEIGHT OF SOIL SOLIDS (?s) = Ws/Vs
12. Specific Gravity of SolidsThe specific gravity of soil particles (G) is defined as the ratio of the mass of a given volume of solids to the mass of an equal volume of water at 4° C.
G = ?s/?wThe mass density of water ?w at 4°C is 1gm/ml, 1000 kg/m3 or 1 Mg/m3
Basic Soil Relationships
|Sl No||Relationship in mass density||Relationship in unit weight|
|1||n = e/(1+e)||n = e/(1+e)|
|2||e = n/(1-n)||e = n/(1-n)|
|3||na = n ac||na = n ac|
|4||?= (G+Se)?w/(1+e)||?= (G+Se) ? w/(1+e)|
|5||?d = G?w/(1+e)||?d = G ? w/(1+e)|
|6||?sat = (G+e)?w/(1+e)||?sat = (G+e) ? w/(1+e)|
|7||?' = (G-1)?w/(1+e)||?' = (G-1) ? w/(1+e)|
|8||e = wG/s||e = wG/s|
|9||?d = ?/(1+w)||?d = ?/(1+w)|
|10||?d = (1-na)G ?w/(1+wG)||?d = (1-na)G ? w/(1+wG)|