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PREFACE:
This book by Vardoulakis and Sulem is an outstanding contribution to the important field of geomechanics and will also be use fulto the many branches of engineering and applied science, particularly those dealing with mechanical behavior.
Following a self-contained Introduction, chapter 2 introduces the basic concepts from continuum mechanics and thermodynamics before the incremental formulation of standard continuum mechanics, particularly useful for stability and bifurcation problems, is presented in chapter 3. This formalism is employed in chapter 4 to analyze in detail buckling and interface instabilities, including multilayered and cracked media which offer a natural stimulus for introducing the concept of Crosserat continuum.
Chapter 5 provides an updated contribution to the mechanics of water-saturated media. It takes Biot’s original contributionto a new level of understanding, including important physical phenomena such as grain crushing and non-Darcean flow. It uses the essentials of mixture formalism but achieves a great economy of postulates and mathematical generalizations with nodirect physical interpretation.
In the same spirit, chapters 6 to 8 provide self-contained reviews of the current plasticity theories and discuss in a systematic and thorough manner the problems of bifurcation and shear-band formation. The effects of non-coaxiality, confining pressure and grain characteristics are explained.
The benchmark problems of the triaxial compression test, the biaxial compression testand the cavity inflation test are analyzed in detail as examples of loss of material stability and progressive failure.
The stage has now been set for the introduction of higher order continuum models to describe correctly bifurcation and periodic phenomena in granular materials. Standard theories of soil plasticity do not contain an internal length scale, and thus features such as thickness and spacing of shear bands, as well as the stress-strain response in the softening regime, cannot be addressed.
As a result, finite element calculations do not converge and related boundary value problems are ill-posed. The authors were among the first to show that Cosserat and higher order gradient plasticity models can resolve these difficulties.
Self-contained accounts of Cosserat plasticity and second-grade plasticity are given in chapters 9and 10, respectively.
Bifurcation and shear-band analyses are performed and the necessity of higher order terms in removing ill-posedeness in the softening regime with simultaneous determination of shear-band characteristics (not captured by standard continuum theory) is documented.
The book concludes with an account of stability of undrained deformations. This problem is complex and very little understood despite its practical importance. The authors demonstrate that fundamental workcan intelligibly be applied to solve outstanding geomechanics problems with extended engineering implications.
Careful laboratory tests are used to calibrate the theoretical models. This well-organized volume is a substantial and valuable reference for civil engineers and geologists, as well as mechanical engineers and metal physicists.
It should be of value to any junior or senior researcher with a keen interest in the stability of deformation.
