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Dive into the research topics where Christian Saix is active.

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Featured researches published by Christian Saix.


Canadian Geotechnical Journal | 2010

Definition and experimental determination of a soil-water retention surface

Simon Salager; M S El Youssoufi; Christian Saix

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.


Geotechnical special publication | 2007

Compression tests on a sandy silt at different suction and temperature levels.

Bertrand François; Simon Salager; M. S. El Youssoufi; D. Ubals Picanyol; Lyesse Laloui; Christian Saix

This paper presents a unified thermo-mechanical experimental study on a remoulded unsaturated sandy silt and brings a contribution to the understanding of the fundamental mechanics of unsaturated soils in non- isothermal conditions. The experimental program was carried out at four temperatures and four suction levels using two thermo-hydro-mechanical (THM) cells, one isotropic and the other oedometric. The effect of suction and temperature on the compressibility and on the apparent preconsolidation pressure of the soil is addressed. Finally, an analytical expression of the evolution of the apparent preconsolidation pressure with respect to temperature and suction is proposed.


Geo-Denver 2007 | 2007

Experimental study of the water retention curve as a function of void ratio

Simon Salager; M. S. El Youssoufi; Christian Saix

This article presents an experimental study of the water retention curve involving the measurement of void ratio on a drying path. Tests were conducted to determine the variations of water content w and void ratio e induced by variations of the suction s. This study concerns the whole hydric domain of the soil from saturation to dry state. To determine the water retention curve, we used a pressure cell for low suctions and a vapor equilibrium technique (salt solutions) for high suctions. This water retention curve is based on the constitutive relation between water content and suction, for a given void ratio. From saturation, this curve was investigated for different initial states due to different conditions of soil compaction. The results lead to the plotting of a characteristic surface w=w(s,e) which expresses water content as a function of suction and void ratio. It can be considered as a generalization of the classical retention curve. Moreover, this curve can be represented using the degree of saturation as function of suction and void ratio.


Archive | 2007

Influence of Temperature on the Water Retention Curve of Soils. Modelling and Experiments

Simon Salager; Moulay Saïd El Youssoufi; Christian Saix

We investigate the influence of temperature on the retention curve of soils. This curve represents the constitutive relation between water content w and suction s, for a given temperature T and a given void ratio e. We present a model based on the differential of suction as a function of T, w and e. When adjusted for a retention curve obtained at a given temperature, this model enables to predict this curve for any temperature. In parallel, we carried out experiments on a clayey silty sand by using a pressure cell immersed in a thermostatic bath. The model was validated by several tests on the clayey silty sand at 20 and 60˚ C. The application of the model to data found in the literature confirms its predictive power for a wide range of porous materials. These results allow us to plot the retention surface, from experimental tests obtained at a given temperature and from modelling. It can be considered as a generalization of the classical retention curve. Finally, we discuss the influence of the void ratio variation during experiments on the curve predicted by the model.


Archive | 2007

Effect of Capillary and Cemented Bonds on the Strength of Unsaturated Sands

Fabien Soulié; Moulay Saïd El Youssoufi; Jean-Yves Delenne; Christian Saix

The cohesive interactions between grains play a prevailing role in the mechanical behaviour of unsaturated granular materials such as fine sands. These interactions are generally bonds of various natures that evolve according to the surrounding hygrothermic conditions. We study the case where the liquid present in the material is a water solution saturated with sodium chloride. The bonds are then of capillary type and the cohesive interactions are mainly attractive. In this case, the mechanical strength in an unconfined compression test is relatively low. At low relative humidity, the phase change of water involves a crystallization of salt at the contact points between grains generating thus bonds of solid type. The mechanical strength of the material is thus enhanced. An experimental study of the variation of the mechanical strength during the crystallization of salt allowed us to show two distinct cohesive regimes: capillary and cemented. The transition between these two regimes does not seem to be correlated with the mass of the crystallized salt, but rather with the residual degree of saturation. An analysis of these results is proposed by comparison with numerical simulations based on the discrete element approach.


Archive | 2012

Capillary Cohesive Local Force: Modelling and Experiment

Fabien Soulié; Moulay Saïd El Youssoufi; Fabien Cherblanc; Christian Saix

The capillary cohesion in granular media is studied at the local scale of a doublet of particles by theoretical and experimental ways. An explicit relation is proposed to describe the cohesive force as a function of the characteristics of the doublet. Taking into account contact, capillarity, and rupture aspects, a local cohesive law is established. This law is integrated in a 3D numerical code in order to estimate the influence of the local cohesion on the macroscopic behaviour of granular media.


Archive | 2005

Thermo-mechanical Behaviour of a Soil. Yield Surface Evolution

Moulay Saïd El Youssoufi; Christian Saix; Frédéric Jamin

This paper presents a study of temperature influence on the yield surface for saturated and unsaturated soils. It lies within the framework of characterization and modelling of soil behaviour on thermo-hydro-mechanical loading. In this study, clayey silty sand samples are subjected to mechanical consolidation tests at different temperatures and fixed suctions. These experimental tests make it possible to determine the yield surface evolution according to temperature ranging between 20°C and 60°C. For the studied soil, the experimental study shows a thermo-extensible nature of the yield surface. An explanation of this result is proposed while gone by microscopic considerations in touch with capillary meniscuses evolution according to temperature and suction.


International Journal for Numerical and Analytical Methods in Geomechanics | 2006

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

Fabien Soulié; Fabien Cherblanc; M. S. El Youssoufi; Christian Saix


Soils and Foundations | 2008

Experimental investigations of temperature and suction effects on compressibility and pre-consolidation pressure of a sandy silt

Simon Salager; Bertrand François; M. S. El Youssoufi; Lyesse Laloui; Christian Saix


Canadian Geotechnical Journal | 2000

Éléments de couplage thermomécanique dans la consolidation de sols non saturés

Christian Saix; P. Devillers; M S El Youssoufi

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Fabien Soulié

University of Montpellier

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Simon Salager

Centre national de la recherche scientifique

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Simon Salager

Centre national de la recherche scientifique

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Bertrand François

Université libre de Bruxelles

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