Modern Trends in Geomechanics




1 Introduction

Some of the earliest applications of energy arguments to develop conceptual

models for the behaviour of soils, sands and other geomaterials are those establishing

stress–dilatancy relations due to Taylor [35] and Rowe [31]. The

original formulations of the Cam Clay, critical state models was based upon

concepts of the plastic dissipation of energy. More recently, energy arguments,

based upon the laws of thermodynamics have been used to establish general

procedures for constitutive modelling [37]. One of the best known thermomechanics

formulations is due to Rice [29]. However this has a built in “normality

structure” and is not appropriate for frictional geomaterials which commonly

exhibit non-normal flow rules. Here we use the line of development described

in the books by Ziegler [40], Maugin [21] and papers by Collins and Houlsby

(1997) and Houlsby and Puzrin [18], who coined the term “hyper-plasticity”

for this approach. The characterizing feature of the hyper-plastic approach is

that the complete elastic–plastic constitutive behaviour, including yield conditions

and flow rules, can be determined from two thermomechanical potentials,

the free energy and the dissipation rate.


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