The Void Ratio is basically related to porosity especially when porosity is expressed as a ratio. This equation calculates the ratio of volume occupied by voids (`V_V`) to volume occupied by soil solids(`V_S`).
If void ratio is high (loose soils) voids in a soil skeleton tend to minimize under loading - adjacent particles contract. However, when void ratio is relatively small (dense soils), then the volume of the soil is vulnerable to increase under loading - particles dilate.