What does "swell" indicate in earth volume measurement?

In earth volume measurement, "swell" specifically refers to the increase in volume that occurs when soil is excavated and transitions from its natural (in-situ) state to a loose state. This phenomenon occurs due to the air that gets trapped between the soil particles when the soil is loosened.

When soil is compacted, the density increases and the volume decreases, leading to a reduction in volume from the loose state to a compacted state. However, during excavation, soil expands, resulting in a volume increase given that the particles can spread apart more freely.

This understanding is essential for calculating the amount of soil required for fill operations or for estimating the volume after excavation, as failing to account for swell could lead to significant discrepancies in project planning and material usage.