Failure in granular materials: macro and micro views -- Instability in Loose Sand: Experimental Results and Numerical Simulations with a Microstructural Model.-Failure in granular materials in relation to material instability, fabric and plastic flow issues.-Loss of controllability in partially saturated soils -- Critical plane approach to analysis of failure criteria for anisotropic geomaterials.-A simple method to consider density and bonding effects in modeling of geomaterials.-Cyclic mobility of sand and its simulation in boundary value problems.-An updated hypoplastic constitutive model, its implementation and application -- A Chemo-Thermo-Mechanically Coupled Analysis of Ground Deformation Induced by Methane Hydrate Dissociation.-Model for Pore-Fluid Induced Degradation of Soft Rocks.-Natural Processes and Strength Degradation.-Local behavior of pore water pressure during plane-strain compression of soft rock -- FE investigations of dynamic shear localization in granular bodies within non-local hypoplasticity using ALE formulation.-Concurrent multiscale computational modeling for dense dry granular materials interfacing deformable solid bodies.-Performance of SPH method for deformation analyses of geomaterials.-CIP-based Numerical Simulation of Snow Avalanche -- A Mesh Free Method to Simulate Earthmoving Operations In Fine-Grain Cohesive Soils.-Analysis of deformation and damage processes in soil-tool interaction problems.-Modeling Excavator-Soil Interactions.

Geomaterials exhibit complex but rich mechanical behaviour with a variety of failure modes ranging from diffuse to localized deformation depending on stress, density, microstructure, and loading conditions. These failure modes are a result of an instability of material and/or geometric nature that can be studied within the framework of bifurcation theory. Degradation is another related phenomenon arising from cyclic loading, ageing, weathering, chemical attack, and capillary effects, among others. The methodology of analyzing the various types of instabilities is crucial in the adequate modelling and safe design of numerous problems in geomechanics. The present volume contains a sampling of enlarged versions of papers presented at the International Workshop on Bifurcation and Degradations in Geomaterials (IWBDG 2008) held in Lake Louise, Alberta, Canada, May 28-31, 2008. These papers capture the state-of-the-art in the specialized field of geomechanics and contemporary approaches to solving the central issue of failure. Some engineering applications are presented in the areas of energy resource extraction and soil-machine interaction.