ABSTRACT
SOIL CONSISTENCY With varying water content, a soil may be solid, plastic or liquid. Most natural clays are plastic. Water content (w) weight of water as % of dry weight. Consistency limits (Atterberg limits) are defined as: Plastic limit (PL) minimum moisture content where a soil can be rolled into a cylinder 3 mm in diameter. Disturbed soil at PL has shear strength around 100 kPa. Liquid limit (LL) minimum moisture content at which soil flows under its own weight. Disturbed soil at LL has shear strength around 1 kPa. Plasticity index (Pl) LL-PL. This refers to the soil itself and is the change in water content required to increase its strength 100 times; it is the range of water content in which the soil is plastic or sticky. High Pl soils are less stable, with large swelling potential. Liquidity index (Ll) (w-PL)/Pl. This is a measure of soil consistency and strength at a given water content.
