Void ratio


The void ratio of a mixture is the ratio of the volume of voids to volume of solids.
It is a dimensionless quantity in materials science, and is closely related to porosity as follows:
and
where is void ratio, is porosity, VV is the volume of void-space, VS is the volume of solids, and VT is the total or bulk volume. This figure is relevant in composites, in mining, and in soil science. In geotechnical engineering, it is considered as one of the state variables of soils and represented by the symbol e.
Note that in geotechnical engineering, the symbol usually represents the angle of shearing resistance, a shear strength parameter. Because of this, the equation is usually rewritten using for porosity:
and
where is void ratio, is porosity, VV is the volume of void-space, VS is the volume of solids, and VT is the total or bulk volume.

Engineering applications