What is Submerged Density and Degree of Shrinkage?

Submerged density :- Submerged specific gravity is equal to the specific gravity given by the ratio of the weight of the object to the weight of the fluid minus one. That is the object and fluid have the same density when the specific gravity equals one and the submerged specific gravity equals zero. Degree of Shrinkage :- It is defined as decrease in volume of soil expresses as the percentage of original volume when water content of the soil is reduced from its present state to shrinkage limit.

Submerged density or bouyant density is the density of a mass of soil as observed under water in a saturated condition of course. Suppose you are calculating the density when the soil mass and you yourself are submerged. It is calculated as the difference of the soil density in air and the density of water, divided by the density of water.

SD = (density of soil - density of water) / density of water

or

SD = density of soil in air - 1

It is also defined as the mass of soil minus the mass of water displaced by it upon submergence, divided by the volume.

This concept is particularly useful in determining the bouyancy of submerged soils and is crucial in equations of sediment transport in rivers. If the bouyant density equals 1, the soil just floats. If it gets negative, soil will rise in water.

Degree of shrinkage is another concept. It is the amount of water content reduction needed to bring the soil to its shrinkage limit, expressed as percent of the original water content.

1. Submerged Density : Generally when the soil is below water table, it is known as submerged soil. For a submerged soil, a buoyant force acts on the soil . Due to this buoyant force the net weight of the saturated soil will get reduced, the resultant weight will be known as submerged unit weight.  The submerged density is thing but, the submerged unit weight per unit of total volume.
2. Degree of shrinkage (D.O.S.): when the volume of soil is reduced from a particular condition to the shrinkage limit volume (The limit below which reduction in the water content will not reduce the volume of soil)  then what is net reduction of volume has occurred is noted down. this net reduction of volume is divided by the original volume of soil sample gives the degree of shrinkage.

SUBMERGED MASS DENSITY OF SOIL:

It is define as “ The submerged mass of soil per unit volume is called submerged density of soil”

It usually occur when our soil sample present below the water, so that’s why we called it submerged density .

Formulas;

Submerged density = Submerged mass/Volume.

DEGREE OF SHRINKAGE:

It can define as “ Decrease in volume of soil which is expresses as the percentage of  actual volume  when water content of the soil is reduced from it,s present stage to the shrinkage limit.

Degree of Shrinkage basically tells us about the plasticity of soil.

Table:

DOS              PLASTICITY

<5                  Good

5_10             Medium Good

10_15           Poor

>15               Very Poor.