Plasticity and Geomechanics follows on from our earlier book Elasticity and Geomechanics. Like the earlier book, this one is very much a textbook rather than a treatise or reference book. It has grown from lecture notes and is written with students firmly in mind. Hopefully it will provide an easy, accessible introduction to a subject which, while being widely used in engineering practice, is often difficult for students to assimilate. The plasticity of metals is itself a subject of some complexity. When, instead of metals, the material we are concerned with is either soil or rock, the level of complexity is increased significantly. We have attempted here to untangle the ideas and concepts, and to lay out as clear a picture as possible of a subject area that is still in a state of development and discovery.

The book is organised as follows. Chapters 1 and 2 review some of the basic elements of stress and strain as well as the fundamentals of elasticity. Chapter 2 also presents a general discussion of inelastic response in soil, emphasising the defining characteristics of yield under isotropic compression and dilatancy as a result of shearing. Chapters 3 and 4 set out the fundamental ideas of yield surface and flow rules. The geometry of principal stress space is developed in detail. Yield loci for metals, for Coulomb materials and for some modifications of Coulomb materials are all presented. The Cam Clay and Modified Cam Clay surfaces are summarised.