Geomaterials are defined as ‘processed or unprocessed soils, rocks or minerals used in the construction of buildings or structures, including man-made construction materials manufactured from soils, rocks or minerals’ (Fookes, 1991). The definition deliberately includes manmade materials such as bricks or cement but excludes allied engineering materials whose manufacturing is more extensive, such as steel and synthetic paints.

Simply stated, a material model is a mathematical relationship describing the stressstrain behaviour of a small but finite quantity of material, and is often termed a ‘constitutive model’.The formulation of the material model forms an important step in obtaining solutions for practical engineering problems and, once established, it can be employed in a numerical solution code suitable for the analysis of geomechanical structures, with given boundary conditions, material zones and loading.

The first international workshop on soil crushability was held in Sheffield, U.K. on September 1997 and was the origin of a subsequent series of meetings starting with the “International Workshop on Soil Crushability” IWSC’99 atYamaguchi University in Ube, Japan on July 1999. As a result of these workshops, the research area widened from soil crushability to a re-assessment of fundamental aspects of soil mechanics theories using micromechanics.

Geotechnical failures, specially the catastrophic ones, are an excellent experience and a source of inspiration to improve our current understanding of phenomena and our procedures and tools for analysis and prediction. This unconventional manner to learn Geomechanics is the essence of this book. In general, Soil Mechanics and Geotechnical text books describe first the concepts and the theoretical developments and then apply them to interpret or solve a particular application. This book has a different approach. The case (a failure) is first described and then an explanation is sought. This approach is developed through a set of steps which can be summarized as follows.