The first edition of The Mechanics of Soils and Foundations was published in 1993. Its objectives were set out in the Preface to the 1st edition and in the final chapter and they were, I think, largely achieved. It was not, and was not intended to be, a guide to ground engineering: it contained few design charts, few references to standards and codes and no case histories. It has been widely used as an undergraduate and post-graduate text in the more up-to-date university courses in soil mechanics and geotechnical engineering inUKand abroad. Teachers and students liked the very simple treatments of the basic theories of soil mechanics and their applications in analyses of slopes, foundations and retaining walls. Most of the engineers’ offices I have been in have a copy. When Tony Moore of Taylor & Francis approached me to prepare a second edition my initial response was say that I was very happy with the book as it was and couldn’t he simply re-print it. It dealt with basic principles, little had changed in the time since the first edition was published and it was not therefore outdated. However, as I read it again in detail I saw that there were bits missing and there were places where I had not explained things as clearly as I would have liked. So this 2nd edition contains some new material and it includes extensive re-working and clarifications of the original descriptions and explanations; I hope to make them clearer. I have added three new chapters. In the chapter on design parameters I have discussed which strengths, peak, critical state or residual, should be used with different analyses and with what factors. I have distinguished more clearly than before between a factor of safety which is intended to ensure that the structure is safe and a load factor which is intended to limit movements. I have related the basic strength and stiffness parameters of a soil to its classification. I have added a short chapter on unsaturated soils which describes the relationships between soil, water and air and aspects of the behaviour of unsaturated soils. I have added a chapter on soft ground tunnelling because this is an important part of modern ground engineering and the current theories and design methods illustrate the development of practice from a number of different methods of research. As in the 1st edition, I have given a few charts of design parameters for slopes and foundations to illustrate the more common ones. This is a teaching text-book and it describes the basic theories upon which these charts are based. It is not a design manual and I have deliberately made these charts small so you will not be able to obtain reliable values from them. If you are designing a slope, a foundation or a retaining wall you should go to the original design charts or calculate the values you need. I have described some simple experiments which you can do yourself at home or at the beach. These investigate the nature and state of soils and the behaviour of simple slopes and foundations and there are links to the parts of the book which deal with the relevant theories. It is important always to relate the behaviour of these simple models to the theories you are taught at university and to the designs you will do in practice. I am grateful to all those friends and colleagues who have discussed with me soil mechanics and geotechnical engineering and how it should be taught to students. My belief is that university students should know and understand the basic principles which are described in my book. Applications of these theories through standards and codes should be taught only when sufficient time has been given to establishing the basic principles; practice is better learned by practice. I amgrateful for the very detailed comments and criticisms that I received from Eddie Bromhead, Federica Coteccia, Andrew McNamara, Sarah Stallebrass, Neil Taylor and Dave White who introduced me to the problem of the car going up hill which I have used in Chapter 22. I am grateful to my colleagues at City University for allowing me the time to complete this new edition.