Geotechnical engineers, classify soils according to their engineering properties as they relate to use for foundation support or building material. Soils are divided into three major classification groups:
1. coarse-grained soils (e.g. sands and gravels);
2. fine-grained soils (e.g. silts and clays); and
3. highly organic soils, often referred to as peat.
Soils are generally classified via particle size distribution (PSD), and depending on this classification, soils will differ in regards to their permeability properties. In finer particle soils (i.e. silts and clays), the voids spaces between individual particles are smaller and hence offer greater resistance to the flow of water, thereby having lower permeability. Thereby the proportions of clay and silt fractions of a soil are important in determining its permeability.
Bioscience uses both sieve and the hydrometer analysis to determine the PSD and hence its classification and permeability, to either provide the horticultural industries with relevant information to improve productivity or in the case of a Geotechnical Investigation to provide information on soil geomorphology that might impede construction and/or development.