The lowest water content at which the minus #40 fraction remains cohesive enough to hold together when rolled with the fingers on a glass plate or sheet of unglazed paper into a thread 1/8" in diameter.
The lowest moisture content at which a soil can be rolled into a 1/8" diameter thread without breaking.
the plastic limit is a measure of how much moisture a clay soil can take on before the soil becomes moldable like a plastic; the plastic limit is determined by standard geotechnical engineering tests performed in a laboratory; the valve determined should be understood as an approximation since the engineer must make a subjective judgment as to at what point the clay soil behaves like a liquid
The water content of the soil above which the soil will compress and shear when compacted - leading to structural degradation occurs.
(1) The water content corresponding to an arbitrary limit between the plastic and the semisolid states of consistency of a soil. (2) Water content at which a soil will just begin to crumble when rolled into a thread approximately 1/8 in. (3.2 mm) in diameter.
(engineering) the water content at which the soil rolled to a 1/3-cm wire begins to crumble.