It is well known that numerical methods play a very important role in geo- technical engineering and in a related activity called “computational geo- technics”. The area that is covered by computational geotechnics is growing, in particular that which relates to the multiphase nature of geomaterials. This book is the second volume of Computational Modeling of Multiphase Geomaterials that was published in 2012 and provides recent progress in this area, i.e., the basic concept of the air–water–soil mixture, cyclic con- stitutive models, anisotropic models, non-coaxial models, gradient models, strain localization including compaction bands, dynamic strain localiza- tion, and the instability of unsaturated soils. In addition, this book includes the application of computational modeling to slope stability, large-scale excavation of ground, liquefaction analysis of levees during earthquakes, a methane hydrate development-related problem, and the shielding of con- tamination by bentonite. Furthermore, the erosion problem of geomaterials due to seepage flow is presented. In the analyses presented in this book, we used the computer codes “CONVI2D” for the two-dimensional problem and “CONVI3D” for the three-dimensional problem, and several extended codes such as CONVI2D-DY for dynamic analysis, etc. These codes have been developed by the authors and their colleagues in the geomechanics laboratory of Kyoto University.
Chapter 1 deals with the formulation of gas–liquid–solid three-phase porous media with the fundamental concept. The effective stress and skel- eton stresses are derived based on the theory of porous media in the context of the mixture theory of continuum mechanics.