Comportement hydromécanique des sols quasi-saturé comportant de l'air occlus

Cet article présente un modèle hydromécanique qui considère séparément la cinématique et le comportement mécanique de chaque espèce fluide (e.g. l'eau liquide, l'air dissous, l'air gazeux) et de la matrice solide dans les sols quasi-saturé. Une loi de comportement élastique est adoptée pour les phases solide et liquide. Ce nouveau modèle de comportement a été implémenté dans le code de calcul COMSOL Multiphysics. Les simulations numériques permettent de mettre en évidence l'aptitude du modèle à reproduire une transition continue du domaine non saturé au domaine saturé

Definition of a safety factor using the finite element method in geomechanics, from a static to dynamic regime

International audienc

Déplacements induits par les tunneliers : rétro-analyse de chantiers en milieu urbain sur la base de calculs éléments finis en section courante

L’estimation des déplacements induits par le creusement au tunnelier sur des constructions avoisinantes (immeubles, ouvrages d’art, tunnels, réseaux…) est une étape essentielle des projets d’ouvrages souterrains en zones urbaines. De cette estimation sont, en effet, déduits ou adaptés des choix forts de conception tels que le tracé du tunnel, le dimensionnement du tunnelier (surcoupe, conicité…) et le choix de ses paramètres de pilotage (pression frontale, pression de bourrage…). Cet article présente des comparaisons entre les résultats de calculs éléments finis 2D et six sections instrumentées d’ouvrages réels. L’ensemble des paramètres nécessaires à la modélisation (modèle géotechnique et paramètres de creusement du tunnelier) est décrit de manière explicite. Ces rétro-analyses permettent de mieux cerner les paramètres clés du problème, en particulier le rôle majeur des pertes de volume induites le long de la jupe du tunnelier

Une méthode pour évaluer un tenseur capillaire dans les sols non saturés

International audienceUne méthode pour évaluer un tenseur capillaire dans les sols non saturé

Vibrations induced by tunnel boring machine in urban areas: In situ measurements and methodology of analysis

Excavation with tunnel boring machine (TBM) can generate vibrations, causing damages to neighbouring buildings and disturbing the residents or the equipment. This problem is particularly challenging in urban areas, where TBMs are increasingly large in diameter and shallow in depth. In response to this problem, four experimental campaigns were carried out in different geotechnical contexts in France. The vibration measurements were acquired on the surface and inside the TBMs. These measurements are also complemented by few data in the literature. An original methodology of signal processing is proposed to characterize the amplitude of the particle velocities, as well as the frequency content of the signals to highlight the most energetic bands. The levels of vibrations are also compared with the thresholds existing in various European regulations concerning the impact on neighbouring structures and the disturbance to local residents

TBM soft ground interaction: Experimental study on a 1 g reduced-scale EPBS model

International audienc

Theoretical modelling of retention curve for Livet-Gavet loam

Different approaches have been used for modeling retention curves. The experimental correlation was first proposed [1-3]. The physical modelling of unsaturated soils is used for this study. The shape of the retention curve is a consequence of physical assumptions. The paper presents a theoretical model based on elastic spherical particle arrangement. Firstly, a uniform model is presented with a single diameter of soil particle. The second step extends the use of the model to graded soils. The model uses only physical parameters easy to measure. The model is compared with the experimental retention curve of two different samples, the Livet-Gavet loam (1.61m-3mm) as paste and the Gavet sandy loam compacted with 85 falls per layer of Proctor weight. It shows its ability to model the experimental curves. It is of great interest for engineers as it uses only physical parameters. It gives a direct determination of the retention curve along the wetting path and along the drying path. It shows also the importance of adsorbed water to describe the retention curve

Loading-unloading shear behavior of rammed earth upon varying clay content and relative humidity conditions

International audienc

Modelling the poroplastic damageable behaviour of earthen materials

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Elastoplastic model for unsaturated, quasi-saturated and fully saturated fine soils

In unsaturated soils, the gaseous phase is commonly assumed to be continuous. This assumption is no more valid at high saturation ratio. In that case, air bubbles and pockets can be trapped in the porous network by the liquid phase and the gas phase becomes discontinuous. This trapped air reduces the apparent compressibility of the pore fluid and affect the mechanical behavior of the soil. Although it is trapped in the pores, its dissolution can take place. Dissolved air can migrate through the pore space, either by following the flow of the fluid or by diffusion. In this context, this paper present a hydro mechanical model that separately considers the kinematics and the mechanical behavior of each fluid species (eg liquid water, dissolved air, gaseous air) and the solid matrix. This new model was implemented in a C++ code. Some numerical simulations are performed to demonstrate the ability of this model to reproduce a continuous transition of unsaturated to saturated states