What is soil relative density ID?

Relative density or density index is the ratio of the difference between the void ratio of a cohesion-less soil in the loosest state and in-situ void ratio to the difference between its void ratios in the loosest and the densest states. It is often used in soil mechanics to characterize the relative compactness of granular soils like sands and gravels.

Here is the step by step process to calculate the soil relative density:

1. Determine the in-situ void ratio (e) of the soil sample. This can be done by determining the volume of voids and the volume of solids in the soil sample.

2. Determine the void ratio of the soil in its loosest state (emin). This can be done by loosely filling a container with the soil and determining the volume of voids and the volume of solids.

3. Determine the void ratio of the soil in its densest state (emax). This can be done by compacting the soil in a container and determining the volume of voids and the volume of solids.

4. Substitute these values into the formula for relative density:

   Id = (emax - e) / (emax - emin) * 100%

The result is the relative density of the soil, expressed as a percentage. A higher relative density indicates a denser soil.