The dry density decreases in cohesion less soil with an increase in water content due to which of the following reasons?

Explanation:

The dry density of cohesionless soils such as sand decreases with a rise in water content mainly because of the phenomenon known as "bulking of sand."

When water is added to sand, a film of water forms around the sand particles leading to the increase in volume or "bulking." This thin film of water pushes the sand particles apart, which leads to an increase in the volume of the sand, consequently reducing dry density.

Additional InformationSeepage:

• Seepage refers to water moving through a porous material due to differences in pressure or water levels. 

Specific Gravity:

• Specific gravity is a measure of the relative density of a substance as compared to the density of water at a standard temperature and pressure. It is a dimensionless unit.

Capillary Rise:

• Capillary rise refers to the ability of a liquid to flow in narrow spaces against the force of gravity. It is caused by the combination of adhesive forces of the liquid to the walls of the container or soil pores, and cohesive forces within the liquid. In soil, capillary rise can indeed bring moisture to otherwise dry areas and may cause some changes to the structure and density of the soil.