Residual soils are found in many parts of the world and are used extensively as construction materials for roads, embankments and dams, and to support the foundations of buildings, bridges and load-bearing pavements. The characteristics and engineering properties of residual soils can differ significantly from those of the more familiar transported soils. The fact that residual soils occur often in areas with tropical and sub-tropical climates and (extensively) in semi-arid climates, adds another dimension to their engineering performance, that of unsaturation.

Although there are...