Thisbookisacollectionof31paperspresentedattheInternationalWorkshop on Modern Trends in Geomechanics, held on 27¿29 June 2005 in Vienna. This workshop was run under the motto to bring together di?erent schools of thought in geomechanics research. The workshop was attended by about 50 participants from 15 countries. Besides the presentations, the workshop also o?ered welcoming occasions for stimulating discussions. The contributions in this book cover a wide range of topics from applied mathematics to geoengineering applications, re?ecting the breadth and depth of geomechanics research. The articles are peer reviewed and arranged in six parts: general aspects, constitutive modelling, micromechanics, analytical and numerical methods, granular materials and engineering applications. Wewouldliketothankallcontributorsfortheirdiligencetoprovidetimely their contributions. The generous support received from the following orga- zations is gratefully acknowledged: ¿ Alpine Mayreder Construction Ltd ¿ Bank Austria ¿ Credit Institute ¿ Austrian Geomechanics Society Our thanks also go to the managing editors at Springer, in particular Ms. Heather King and Dr. Thomas Ditzinger, who have enabled the qu- ity publication of this book at reasonable price. Last but not least, we would like to express our thanks to our co-workers in Vienna and Nottingham for theirhelpduringtheworkshop.Inparticular,oursecretaries,AnkePriewasser (Vienna) and Caroline Dolby (Nottingham), deserve our heartfelt thanks for their e?ort in organising the workshop and compiling this book.

General Aspects.- Energy Methods for Constitutive Modelling in Geomechanics.- Physical Background of Hypoplasticity.- Thermodynamics of Porous Continua.- Effective Stress Formulation of Unsaturated Soil Mechanics.- Progress in Binary Medium Modeling of Geological Materials.- Constitutive Modelling.- Generic Constitutive Ingredients in CSSM Models for Sands.- State Boundary Surface in Hypoplasticity.- Modelling of Bonded Soils with Unstable Structure.- An Evaluation of Different Constitutive Models to Predict the Directional Response of a Reconstituted Fine-Grained Soil.- Two Elastoplastic Models for Small and Large Strains and Their Use in Engineering Practise.- Elastic Visco-Plastic Models for the Time-Dependent Stress¿Strain Behaviour of Geomaterials.- Micromechanics.- Micro-Polar Effects under Monotonic and Cyclic Shearing.- Modeling the Post-localization Regime with Local Second Gradient Models: Non-uniqueness of Solutions and Nonpersistent Shear Bands.- Confined Compression and Rod Penetration of a Dense Granular Medium: Discrete Element Modelling and Validation.- Application of Discrete Element Method to Geomechanics.- The Role of Particle Crushing in Granular Materials.- Micromechanical Study of Damage and Permeability Variation in Brittle Rocks.- Analytical and Numerical Methods.- Hydrologically Driven Slope Failure Initiation in Variably Saturated Porous Media.- A Survey of Some Mathematical Results for Highly Frictional Granular Materials.- Double-Slip and Spin: Dilatant Shear in a Reduced Cosserat Model.- The Linear Matching Method for Limit and Shakedown Analysis.- On Recent Analytical Results for Advective Transport in Fluid-Saturated Porous Media.- Granular Materials: Theory and Experiment.- Unusual Soil Behaviour and its Challenge to Constitutive Modelling.- Histotropy of Hostun RF Loose Sand.- Incremental Nonlinearity in Phenomenological and Multiscale Constitutive Relations.- Long-term Deformations in Soils due to Cyclic Loading.- On the Factors Affecting the Formation of Shear Band Systems in Non-Cohesive Soils Under Extensional Strain.- Acceleration Waves in Hypoplasticity - 2D Analysis.- Engineering Applications.- Static and Cyclic Behavior of a Silty Sand According to Tests on Undisturbed Samples.- The Role of Analysis in Non-Displacement Pile Design.- Assessment of Uncertainties in Wellbore Stability Analysis.