The following properties of soils are used by geotechnical engineers in the analysis of site conditions and design of earthworks, retaining structures and foundations.
Unit Weight
Total unit weight: Cumulative weight of the solid particles, water and air in the material per unit volume. Note that the air phase is often assumed to be weightless.
Dry unit weight: Weight of the solid particles of the soil per unit volume.
Saturated unit weight: Weight of the soil when all voids are filled with water such that no air is present per unit volume. Note that this is typically assumed to occur below the water table.
Porosity
Ratio of the volume of voids (containing air and/or water) in a soil to the total volume of the soil expressed as a percentage. A porosity of 0 per cent implies that there is neither air nor water in the soil.
Void ratio is the ratio of the volume of voids to the volume of solid particles in a soil. Void ratio is mathematically related to the porosity and is more commonly used in geotechnical formulae than porosity.
Permeability
A measure of the ability of water to flow through the soil, expressed in units of velocity.
Consolidation
As a noun, the state of the soil with regard to prior loading conditions; soils can be under-consolidated, normally consolidated or over-consolidated.
As a verb, the process by which water is forced out of a soil matrix due to loading, causing the soil to deform, or decrease in volume, with time.
Shear strength
Amount of shear stress a soil can resist without failing.
Atterberg limits
Liquid limit, plastic limit and shrinkage limit related to the plasticity of a soil. It is used in estimating other engineering properties of a soil and in soil classification.
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