Specific Gravity of soil

 Specific Gravity 

The ratio of the mass of a solid or liquid to the mass of an equal volume of distilled water at 4°C (39°F) 

or 

of a gas to an equal volume of air or hydrogen under prescribes conditions of temperature and pressure.

Determination of specific Gravity 

Specific gravity can be determined by the Pycnometer or by 500 ml flask or by  50 ml density bottle 

Note (Important)

Pycnometer 900 mL →if water used in Pycnometer for determination of specific gravity then it is only for coarse grain soil.

If we used Kerosene oil for determination of specific gravity then Pycnometer can be used for both type of soil i.e fine grained soil and coarse grained soil. 

500 mL flask →Can be used both type of Soil fine soil and caorse grained soil  ( in water or kerosene oil)

50 ml density bottle →Can be used both type of Soil fine soil and caorse grained soil( in water or kerosene oil) 

Steps 

(1) Take an empty Pycnometer and weight it ,it is M1 

(2)Fill dry soil into Pycnometer and weight it its M2 

(3)Stirred the sample and fill the water to the top of Pycnometer its weight M3.

(4)Now fill the water in empty Pycnometer and weight it , it is M4 .

Important point 

(a)-It is defined only cohesionless soil.

(b)-This method does not use in cohessive soil 

***because when we stirring the soil then air does not remove due to interlocking if soil particles in cohessive soil. 

We know that specific Gravity 

G= (weight of solid in given volume/weight of water in same volume)

Now Md=M2-M1 

Mw= (M4-M1)-(M3-M2) 

G=(M2-M1)/[(M4-M1)-(M3-M2)] 

G=Md/[(M4-M1)-(M3-M2)].

Note  if kerosene is used instead of water then 

=G=Mdx Gk/[(M4-M1)-(M3-M2).

Where Gk= specific Gravity of Kerosene 

 

Use of sepcific gravity of soil in civil  engineering 

In civil engineering, the specific gravity of soil refers to the ratio of the density of soil solids to the density of water. It is a crucial property used to understand soil composition and behavior. 

Here's a brief overview of its uses:

1. **Soil Classification**: Helps in classifying soils based on their density and particle size, which is important for determining their suitability for construction.

2. **Volume Calculations**: Assists in calculating the volume of soil in embankments and fills, as well as in determining the amount of soil needed for a project.

3. **Compaction Control**: Used to ensure soil is compacted properly to achieve the required strength and stability in structures like foundations and pavements.

4. **Density and Moisture Content Relationships**: Helps in understanding the relationship between soil density and moisture content, which is important for predicting soil behavior under different conditions.

The specific gravity of soil is typically determined through laboratory tests and provides valuable insight into soil properties and engineering characteristics.

Soil formation......