Bank, loose and compacted soil volumes
How soil swells when dug and shrinks when compacted, why earthwork uses three volume states, and how to plan hauling and fill.
One pile of soil, three different volumes
The same soil occupies different volumes depending on its state. In the ground it is bank, or in-situ, material with its natural structure intact. Excavate it and the grains loosen and trap air, so the loose volume is larger, which is what a truck or a spoil pile actually holds. Place it in a fill and compact it, and the roller squeezes out air and reduces voids, so the compacted volume ends up smaller than the original bank. Earthwork estimating tracks all three because each answers a different question.
Why swell and shrinkage differ
Swell and shrinkage are not the same percentage and they measure opposite moves. Swell describes bank turning into loose, driven by the bulking that happens the moment you break ground. Shrinkage describes bank turning into compacted, driven by mechanical compaction pushing the soil denser than it was in nature. A soil might swell 25 percent yet shrink only 10 percent, so loose, bank and compacted volumes form a descending or mixed sequence that depends on the two factors you enter.
Using the numbers to plan a job
Contractors haul in loose measure but pay for and place in bank or compacted measure, so converting between states prevents costly mistakes. If a fill needs a certain compacted volume, divide by one minus the shrinkage fraction to find the bank volume to excavate or import. Then multiply that bank volume by one plus the swell fraction to find the loose volume, which sets your truck count. Getting these conversions right avoids both short deliveries and wasted trips.
Where the percentages come from
Reliable swell and shrinkage values come from geotechnical testing, soil boring logs and past project records for the same material. Handbooks list typical ranges: common earth swells roughly 20 to 30 percent, clay more, and sand and gravel less. Moisture, compaction method and the target density all shift the shrinkage figure. Treat published tables as a first estimate and refine them with field data, because a few percentage points across a large site can move thousands of cubic yards.