A new isotropic cell for studying the thermo-mechanical behavior of unsaturated expansive clays

This paper presents a new suction-temperature controlled isotropic cell that can be used to study the thermo-mechanical behavior of unsaturated expansive clays. The vapor equilibrium technique is used to control the soil suction; the temperature of the cell is controlled using a thermostat bath. The isotropic pressure is applied using a volume/pressure controller that is also used to monitor the volume change of soil specimen. Preliminary experimental results showed good performance of the cell

Definition and experimental determination of a soil-water retention surface

This paper deals with the definition and determination methods of the soil-water retention surface (SWRS), which is the tool used to present the hydromechanical behaviour of soils to highlight both the effect of suction on the change in water and total volumes and the effect of deformation with respect to the water retention capability. An experimental method is introduced to determine the SWRS and applied to a clayey silty sand. The determination of this surface is based on the measurement of void ratio, suction, and water content along the main drying paths. These paths are established for five different initial states. The experimental results allow us to define the parametric equations of the main drying paths, expressing both water content and void ratio as functions of suction and initial void ratio. A model of the SWRS for clayey silty sand is established in the space (void ratio - suction - water content). This surface covers all possible states of the soil inside the investigated range for the three variables. Finally, the SWRS is used to study the relations between water content and suction at a constant void ratio and between void ratio and suction at a constant water content

Transferts de chaleur dans la zone non saturée

On propose une méthode d'élaboration de modèles mathématiques permettant d'aborder les applications liées à l'exploitation thermique du sous-sol. Cette méthode, basée sur la thermodynamique des processus irréversibles, est illustrée dans le cas du stockage de chaleur dans les sols non saturés. On présente les résultats expérimentaux d'une aire d'essai de stockage de chaleur ; ces résultats sont utilisés pour : 1) Analyser les modifications provoquées par le stockage dans la couche de sol non saturée. 2) Valider le modèle mathématique et proposer un modèle simplifié du site de stockage

Effect of temperature on water retention phenomena in deformable soils: theoretical and experimental aspects

In this paper, a theoretical and experimental investigation of the effect of temperature on water retention phenomena in deformable soils is presented. A general law expressing the change in suction with water content, temperature and void ratio is proposed theoretically. This law accounts for the influence of density and temperature on water retention. It also provides a general framework which appears to be well-adapted to describe many particular cases. The effect of temperature is studied through a predictive relationship which is established in this framework. This relationship allows us to obtain the water retention curve at any temperature from that at a reference temperature, thus reducing strongly the number of tests required to characterize the thermo-hydraulic behaviour of a soil. The relevance of this relationship was experimentally verified from new tests as well as the results previously reported in the literature. The new tests were performed on two model media, namely, a terracotta ceramic and a clayey-silty sand. The tests taken from the literature concerned two different clays. Comparison between theoretical prediction and experimental data was particularly promising and shows the capability of the model to cover a wide range of soils

Capillary cohesive local force - Modelling and experiment

Inexistan

Influence of water content on the mechanical behavior of granular assemblies

An explicit relation is developed to describe the capillary force in a doublet of two grains of different sizes as a function of the physical and geometrical characteristics. In particular, it depends on the inter-particle distance and on the volume of the liquid bridge. The modeling of capillary force is validated by experiments performed over a capillary doublet. From this theoretical modeling, we propose a local law of interaction by capillary force taking into account contact and friction between particles as well as the rupture of the liquid bridge. This local law is then implemented in a 3D code based on Discrete Element Method (DEM). This code is used to compute the macroscopic behavior of granular materials involving local interactions as capillary forces

Influence of liquid bridges on the mechanical behaviour of polydisperse granular materials

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