Propagation des surfaces de discontinuite dans un milieu elastoplastique -- The Concept of Bifurcation in Geomechanics -- Experimental Aspects -- Third Invariant Dependent Single Yield Surface Model and Localization Conditions for High Porosity Sandstone -- Interpretation of the Scale Effect in Perforation Failure -- Experimental Investigation of Instabilities of Granular Materials in Relation to Dilatancy and Fabric Issues -- Compactive Cataclastic Flow in Tuffeau de Maastricht Calcarenite: Mechanical Deformation & Permeability Reduction -- Local Second Gradient Models and Damage Mechanics: 1D Post-Localization Studies in Concrete Specimens -- Micromechanical Aspects -- Entropy and Material Instability in the Quasi-Static Mechanics of Granular Media -- A DEM Study of Compaction Band Formation -- Shear Zone Formation in 2D Random Granular Specimens within Enhanced Hypoplasticity -- A Rational Approach to Stress-Dilatancy Modelling Using an Explicit Micromechanical Formulation -- Micro-Fracture Instabilities in Granular Solids -- Constitutive Aspects -- Entropy and Material Instability in the Quasi-Static Mechanics of Granular Media -- Modeling the Influence of Pressure and Moisture Content on the Disintegration of Weathered Rockfill Materials -- Shear Zone Formation in 2D Random Granular Specimens within Enhanced Hypoplasticity -- A Rational Approach to Stress-Dilatancy Modelling Using an Explicit Micromechanical Formulation -- Kinematics of Shear Zone Deformation in Soft Sensitive Clays -- Numerical Aspects -- Numerical Analysis of Deformation of Methane Hydrated Contained Soil due to the Dissociation of Gas Hydrate -- Numerical Prediction of Impact Force of Geomaterial Flow against Retaining Structure using CIP Method -- Numerical Simulation of the Cracked Brazilian Disc under Diametral Compression -- Stress Analysis of Multiply Fractured Porous Rocks. Leading international researchers and practitioners of bifurcations and instabilities in geomechanics debate the developments and applications which have occurred over the last few decades. The topics covered include modeling of bifurcation, structural failure of geomaterials and geostructures, advanced analytical, numerical and experimental techniques, and application and development of generalised continuum models etc. In addition analytical solutions, numerical methods, experimental techniques, and case histories are presented. Beside fundamental research findings, applications in geotechnical, petroleum, mining, and bulk materials engineering are emphasised.