Density index (I_D) expressed as

Concept:

Relative density / Density index / Degree of density

The density index is the ratio of the difference between the void ratios of a cohesionless soil in its loosest state and existing natural state to the difference between its void ratio in the loosest and densest states.

\({I_D} = \frac{{{e_{max}} - e}}{{{e_{max}} - {e_{min}}}}\)

where

emax = void ratio of coarse-grained soil (cohesionless) in its loosest state.

emin = void ratio of coarse-grained soil (cohesionless) in its densest state.

e = void ratio of coarse-grained soil (cohesionless) in its natural existing state in the field.

If a natural deposit is in its loosest state, then e = emax

If a natural deposit is in its Densest state, then e = emin

∴ When the natural state of the cohesionless soil is in its loosest form then the relative density will be equal to 0.