Soil–structure interaction is a topic of significant importance in the solution of problems in geotechnical engineering. Conventional and ad hoc techniques are usually not sufficient to understand the mechanism and model the challenging behavior at the interfaces and joints prevalent in most structural and foundation systems. In addition to mechanical loading, the behavior of structures containing interfaces can be affected by environmental factors such as fluids, temperature, and chemicals. Understanding and defining the behavior of engineering materials and interfaces or joints are vital for realistic and economic analysis and design of engineering problems. Hence, constitutive modeling that defines the behavior of the materials and interfaces, related testing, and validation assume high importance. Owing to the complexities involved in many geotechnical problems, conventional procedures based on assumption of the linear elastic and isotropic nature of materials, and limit equilibrium procedures are found to be insufficient. Hence, we need to use modern computer-oriented procedures to account for factors, such as in situ stress, stress path, volume change, discontinuities and microcracking (initial and induced), strain softening, and liquefaction, which are not accounted for in most conventional methods. Hence, the objective of this book is to present various computerbased methods such as finite element, finite difference, and analytical. The details of these methods are presented for the solution of one-, two-, and threedimensional problems. Various constitutive models for geologic media (“solid”) and interfaces, from simple to advanced, are included to characterize appropriately the behavior of a wide range of materials and interfaces. Wherever possible, we have included simple problems that can be solved by hand, which is an essential step to understanding problems requiring the use of computers. A number of examples for one-, two-, and three-dimensional problems solved by using finite element, finite difference, and analytical methods are also presented. As an exercise for students and readers, a number of problems, often with partial solutions, are included at the end many chapters. The book can be used for courses at the graduate and undergraduate (senior) levels for students who have backgrounds in geotechnical, structural engineering, and basic mechanics courses, including matrix algebra and numerical analysis; a background in numerical methods (finite element, finite difference, etc.) will be valuable to understand and apply the procedures in the book. Practitioners interested in the analysis and design of geotechnical structures can benefit by using the book. They can use the available codes or acquire them from sources listed in Appendix 2; most of such codes can be used on desktop and laptop computers. The book can also be useful to researchers to get acquainted with the available developments, and with advances beyond the level of topics addressed in the book. This book presents the contributions of the authors and other persons and covers a wide spectrum of geotechnical problems that extend over the last four decades or so. It emphasizes the application of modern and powerful computer methods and analytical techniques for the solution of such challenging problems, with special attention to the significant issue of material constitutive modeling. Pioneering applications of numerical methods for solution of challenging problems in geotechnical engineering have taken place from the start of the computer age. Over the last few decades, impressive advances have occurred for constitutive modeling of geomaterials and interfaces/joints. Applications of computer and constitutive models for analysis and design are expected to continue and increase. We believe that this book can provide an impetus to the continuing growth.