This book is a treatise that brings together some of the latest international research and advances in the failure of granular geomaterials within a micromechanical approach. It provides a view of the current scientific community on this topic, putting forward relevant methods and efficient tools for analysis. The chapters includes either phenomenological contributions enriched with micromechanical ingredients, or purely micromechanical investigations. Various failure modes that are encountered in geomaterials and their implications in engineering applications are discussed throughout the chapters. The case of porous frictional materials with or without a fluid phase is considered together with the basic roles of the sliding and opening of contacts as a failure mechanism. The influence of grain crushing as a plausible mechanism under a variety of stress conditions and grain topologies is also addressed. Finally, fracture in continuous materials containing grain inclusions is dealt within the context of damage theory.