The bearing capacity of cohesive (plastic) soil, such as silts and clays, is more complicated than the
bearing capacity of cohesionless (nonplastic) soil. In the southwestern United States, surface deposits
of clay are common and can have a hard and rocklike appearance when they become dried-out during
the summer. Instead of being susceptible to bearing capacity failure, desiccated clays can cause heave
(upward movement) of lightly loaded foundations when the clays get wet during the rainy season.
Expansion of clay will be discussed in Chap. 9.