Mechanics is traditionally a part of physics. The title of the book seems thus to be a tautology. However, the word ‘physical' acts as an accent which becomes obvious during the reading of this voluminous work. The author attempts systematically to sort, classify and interrelate the complex web of physical phenomena which are involved in the mechanical behaviour of soils and to present them in the light of present constitutive frameworks of elastoplasticity and hypoplasticity. In the prologue, the reader can discover that the approach to explanation is ‘more geometrico' by means of ‘attractors' because the author ‘got tired by jungle of data and morast of equations'. Although there are still some conceptual equations in the book, the matter is, in the sense of ‘more geometrico', illustrated mainly with diagrams, schemes and sketches.
The reader should definitely start from the beginning with Chapter 1 (‘Introduction') since the author uses a scientific language which is more oriented towards physicists than geotechnical engineers. It is necessary to learn what is meant by ‘representative soil element, state variables, attractors, argotropy, reversals' and many other notions. Sandy soils are addressed as ‘psammoids' and clayey soils as ‘peloids'. Relatively strict distinctions between those two soil types are kept throughout the whole book.
Chapters 2 and 3 (‘Simple psammoids' and ‘Simple peloids', respectively) are a condensed overview of the soil behaviour observed in laboratory tests. Outcomes of laboratory tests are confronted with predictions from elastoplastic and hypoplastic constitutive models for idealised soil elements. Some of those predictions are calculated, whereas some are only guessed and presented qualitatively. The adjective ‘simple' used in the chapter title means that some phenomena are not considered (such as non-homogeneity of the samples, crushable grains, partial saturation or chemical effects), but still the subject is demanding enough. The structure of the sections is very systematic, and could almost be described as pedantic. After a brief overview of ‘critical state soil mechanics and hypoplasticity' the author devotes separate subsections to ‘near state limits, off state limits, cylindrical symmetry, cuboidal deformation and simple shearing'. The text is accompanied by diagrams of relevant stress/strain paths, stress–strain curves and ‘response polars' (called by the author ‘response envelopes' in the past) and a distinction is made between ‘isobaric' and ‘isochoric' shearing. In the case of clayey soils (‘peloids'), rate-dependent (‘argotropic') effects such as ‘creep' and ‘relaxation' are introduced and reviewed within the frameworks of ‘Cam clay plus viscosity' and ‘visco-hypoplasticity'.
On the basis that stress and void ratio are not sufficient state variables for capturing cyclic behaviour (‘repeated reversals'), Chapters 4 and 5 deal with ‘psammoids with reversals' and ‘peloids with reversals'. The necessary ‘hidden variable' is identified as ‘spatial fluctuation of internal forces'. In constitutive models it is included as ‘back stress' (elastoplasticity) or ‘intergranular strain' (hypoplasticity). ‘Sanisand' by Dafalias and co-workers is used as a reference elastoplastic model for the comparative calculations on sand behaviour. No comparison between elastoplasticity and hypoplasticity is presented for the cyclic behaviour of clayey soils, where bubble models are the representatives of the first model group. In the chapter on ‘psammoids', seismically activated viscous effects are taken into account and treated in an energy approach with ‘granular temperature' being the controlling variable.
Chapter 6 (‘Pore fluid') is relatively short and brings notions of ‘permeability, capillarity, partial pressures, hard grains, soft grains' and others. These are required for the understanding of Chapter 7 (‘Bridging gaps'), which covers attraction mechanisms between single grains. The author distinguishes between ‘net attraction, capillarity and solid bridges', respectively, and presents some selected effects from experimental results (partly his own and partly published by others) on unsaturated and cemented soils.
Chapter 8 is entitled ‘Localization' and deals mainly with ‘shear banding' and resulting ‘patterns'. Most experimental observations come from biaxial tests. Only for sands are numerical calculations using the hypoplastic model with ‘polar quantities' presented. They demonstrate the capabilities of the model in capturing a realistic shear band thickness related to the mean grain size. Localisation in clays is treated qualitatively and the roles of pore pressure and ‘argotropy' are emphasised. A few notes on ‘cracking and channelling' are added as well, although it is acknowledged that these effects can hardly be modelled yet.
Fabric is the topic of a short Chapter 9. Two different types of fabric are discussed: first, the configuration of grains and contact forces which can be taken into account by an additional tensorial state variable (‘fabric tensor'), and second, the composition of the grain skeleton which can be expressed either as a ‘mixture' of the constituents or as a ‘sandwich' (layering).
The remaining seven chapters analyse the role of constitutive models in numerical simulations of various boundary value problems, mostly from the field of geotechnical engineering. Starting from boundary conditions (Chapter 10), which include phenomena from different types of contacts and interfaces (liquid–soil, soil–soil, soil–structure and so on) and from construction steps like filling and excavation (termed ‘placement' and ‘removal'), the author proceeds to one-dimensional problems in Chapter 11 (‘One-dimensional evolutions'). The dimensionless representative soil elements from the previous sections of the book are replaced by boundary value problems which have a characteristic length: soil column, infinite slope and cavity expansion. Consolidation, swelling, shear velocity or wave propagation are discussed in the light of the previous chapters, always making the distinction between ‘psammoids' and ‘peloids'.
Plane-strain problems are treated in Chapters 12 (‘Plane-parallel evolutions without SSI') and 13 (‘Plane-parallel evolutions with SSI'), separating the topics with and without ‘soil–structure interaction' (SSI). Outputs from many publications are interpreted and linked to stress paths and evolution curves for relevant quantities. Most discussed results are based on hypoplastic calculations but elastoplasticity is frequently considered qualitatively. Without SSI, the focus is on the slope behaviour of embankments (called here ‘heaps upon a solid base' and ‘upon yielding ground', respectively) and excavations. ‘In-plane' and ‘anti-plane shaking' and ‘faulting' are discussed as well. Topics of SSI include earth pressure (‘rigid guided walls'), bearing capacity of flat foundations (‘guided rigid strips upon yielding ground') and cases of whole (‘rigid and deformable') structures at the ground. Extensive discussion is devoted to ‘strutted and back-tied retaining structures'. Tunnel structures (‘cavities and underground structures') are considered too.
Axi-symmetric problems are discussed in Chapter 14 (‘Axi-symmetric evolutions'). Starting from the analysis of a triaxial test as a boundary value problem and including a few hints on fills, excavations and ring structures, the emphasis is put on ‘penetration' and ‘pile' behaviour. The inclusion of ‘granular flow' in storage silos may seem a little exotic in the context of other geotechnical applications but the treated phenomena are analogue.
Chapter 15 (‘Less symmetric evolutions') deals extensively with boundary value problems which cannot be simplified using one point or one line of symmetry. Here the reader can find typical geotechnical tasks (excavations, dams, tunnels, pile-raft foundations, horizontally loaded piles, slurry trenches) complemented, for example, by problems of transportation engineering like evolution of uneven settlements of pavements and railway tracks.
The last chapter (‘Critical phenomena') is short and not related to model frameworks discussed before. Some thoughts on ‘pattern formation' in shear banding and cracking, respectively, and on ‘deterministic chaos (loss of stability with spontaneous acceleration, internal erosion)' are presented here. Finally, in the Epilogue, a theory called ‘Granular solid hydrodynamics' is announced and found to be promising.
This truly monumental publication is not a book for leisure reading. It is neither a textbook nor a collection of facts. It is a reference book, rather in the style of an encyclopaedia, with a valuable systematic approach, but still remaining subjective. It is a well, full of ideas and new relationships. Some statements may be controversial but the enthusiasm for research and discovery, which can be tracked as a red line through the whole book, justifies this approach. There are many good objective books without passion and inspiration. This one is different and it can be appreciated if absorbed in small portions, like an oriental spice!
