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Bertrand FRANÇOIS


coordonnées


Ecole polytechnique de Bruxelles
Bertrand FRANCOIS
tel 02 650 27 35, Bertrand.Francois@ulb.ac.be
Campus du Solbosch
CP194/02, avenue F.D. Roosevelt 50, 1050 Bruxelles




unités de recherche


Laboratoire de géomécanique [Laboratory of GeoMechanics (LGM-BATir)] (LJV)



projets


Optimisation des sondes géothermiques en système fermé (GeoTherWal) [Optimization of closed-loop borehole heat exchanger (GeoTherWal)]
[With increasing worldwide energy consumption, improvement and assessment of renewable energy sources is significant nowadays. Geothermal energy, one of the renewable energy sources, is the form of energy stored as heat in the underground, and within a range of 0-400m depth stored heat is categorized as shallow geothermal energy. Beside some traditional applications (e.g. bathing and recreation), this energy can be used for instance in space heating and cooling, and commonly this type of utilization is referred to as direct use. One of the most common used ground source heat pump (GSHP) technologies, closed-loop systems, comprise a vertical (or horizontal) borehole heat exchanger (BHE) installed inside a borehole and a heat pump that circulates a solution of water or anti-freeze mixture through the buried pipes. Thus, the stored heat in the subsurface is transferred across the pipes. The total of the length of the BHE is based on the required amount of energy and the type of underground.. In the objective of maximizing the thermal transfer between the pipes and the ground, the geometry of the borehole heat exchanger and the properties of the grouting material must be optimized. To evaluate and optimize the performance of the geothermal system, the global problem is decomposed into two sub-problems: the near-field behaviour (at the level of the borehole heat exchanger) and the far-field behaviour (in the surrounding ground). Each problem is addressed from the double point of view of experimental developments and numerical analysis.]

Caractérisation expérimentale du traitement à la chaux d'un mélange sable-bentonite [Experimental characterization of the lime treatment of sand-bentonite mixture]
This research focuses on the influence of the lime-treatment on sand-bentonite mixtures. In reality, the variety of natural soils and the disruptive elements do not allow comparing these soils to each other and giving any quantitative conclusions in terms of mechanical improvement. The goal of this study is to build a progressive comprehension of this phenomenon by avoiding any disruptive elements and controlling the most part of the parameters. Consequently, it is considered to study a synthetic soil by controlling its particle size and composition. As a first step, relatively conventional experimental tests in soil mechanics are performed: uniaxial compression tests and indirect traction tests.Actually, sand takes an important part into soil stabilization meaning that a soil containing a lot of clay does not necessary give the best mechanical characteristics.More specific experiments are carried out in order to characterized the physico-chemical reactions of the lime with soil at the particle scale: X-Ray Computed Tomography images (Figure 2), Leroux tests (to determine the amount of aluminate and sulfate created during the reaction), X-Ray diffraction, ... [This research focuses on the influence of the lime-treatment on sand-bentonite mixtures. In reality, the variety of natural soils and the disruptive elements do not allow comparing these soils to each other and giving any quantitative conclusions in terms of mechanical improvement. The goal of this study is to build a progressive comprehension of this phenomenon by avoiding any disruptive elements and controlling the most part of the parameters. Consequently, it is considered to study a synthetic soil by controlling its particle size and composition. As a first step, relatively conventional experimental tests in soil mechanics are performed: uniaxial compression tests and indirect traction tests.Actually, sand takes an important part into soil stabilization meaning that a soil containing a lot of clay does not necessary give the best mechanical characteristics.More specific experiments are carried out in order to characterized the physico-chemical reactions of the lime with soil at the particle scale: X-Ray Computed Tomography images (Figure 2), Leroux tests (to determine the amount of aluminate and sulfate created during the reaction), X-Ray diffraction, ...]

Etude du comportement des sols non-saturés compactés avec la prise en compte de leur traitement à la chaux [Study on the behavior of unsaturated compacted soils with the consideration of their lime-treatment]
[In this study, we use the concepts of unsaturated compacted soil mechanics and extend them to consider their lime-treatment. Unsaturated soils are multiphasic and heterogenic materials. These characteristics imply an important complexity of the soil behavior. Indeed, the mechanical response depends on the water retention behaviour. In addition, the microstructure of the soil, affected by the way the soil is compacted, plays also an important role on its mechanical behaviour. The stress-strain relations obtained from experimental tests (triaxial tests, oedometric compressions, uniaxial compressions) are used as input values for the development of the model.This work is divided in two main parts. The concepts of unsaturated soil mechanics are first applied to untreated soil. So doing, a behavioural law for compacted unsaturated soil is developed. Then, this constitutive framework will be extended to the consideration of the soil treatment with lime. The soil suction (linked to its water content) is a key parameter that relates the behaviour of both untreated and treated materials (the efficiency of the treatment with lime being strongly related to the water content of the material). So, a rigorous quantification of the water retention curve (relating suction to water content or degree of saturation) is essential.]

Modélisation et expérimentation de l'endommagement de roche sous charge explosive en exploitation minière: Application au mines de bauxite guinéenne [Modeling and experimentation of rock damage under blasting mining. Application to mines of Guinea]
[This thesis aims to develop a model with double scales of dynamics damage of rock using the asymptotic homogenization method, this through a powerful modeling and simulations that use advanced numerical methods. The results of this modeling would make it possible to obtain the macroscopic behavior of damage through the observation on a microscopic scale. And subsequently to identify the parameters influencing the fragments size.]



disciplines et mots clés déclarés


Accompagnement des mourants Construction sous-oeuvre

borehole heat exchanger damage model drilling environemental geomechanics geothemal energy homogenization lime treatment rock dynamics soil stabilization sustainable development unsaturated soil