What Is Void Ratio?

Void ratio is a measurement that determines the ratio of voids to solid volumes. It is represented in the equation e= (V_v) / (V_s). V_v represents the voids, and V_s represents the solids.

Typically used for soil, void ratio calculates the consistency of a substance. The void can either be an empty space or a space that is filled with liquid. The solid can be any material that is not liquid. Void ratio is typically used with soil porosity (n). Soil porosity is defined as the ratio of the volume of voids to the complete soil volume. The two ratios often work parallel to each other in the following equations: e= n/(1-n) and n= e/(1+e).

The void ratio value depends on the consistency of the soil and how it is packed. Compaction is the major determining factor of void ratio. Gravel that is well-graded and contains few or no fines has a void ratio that is close to 0.26 minimum and 0.46 maximum. Organic silts and clays with a low level of plasticity generally have a void ratio that is between 0.74 minimum and 2.26 maximum. Some substances have a specific void ratio. For example, soft glacial clay has a void ratio of 1.20.