SOIL COMPACTION

Increasing the density of soils, along with its side effects of increased strength and decreased permeability, is usually desirable in earthwork construction and below building foundations. Compaction is accomplished by use of heavy equipment. In sands and gravels, the equipment usually vibrates, to cause re-orientation of the soil particles into a denser configuration. In silts and clays, a sheepsfoot roller is frequently used, to create small zones of intense shearing, which drives air out of the soil. The result of soil compaction is measured by determining the bulk density and optimum moisture of the compacted soil and comparing it to a maximum dry density, for example, obtained from a Proctor compaction test, to determine the relative compaction.