PhD position : “Field investigation of an in-situ soil treatment solution for clay shrink-swell inhibition”

Thèses - 3 ans Publication : 04/11/2024
The cycles of clay shrink-swell (CSS) are linked to the cycles of soil moisture fluctuations, themselves governed by alternating precipitation and drought periods. In France, 54% of constructions are located in areas characterised by a medium to high hazard of CSS. Structural damages to constructions caused by CSS are estimated at several hundred million euros annually, making CSS the second largest category for natural disaster compensation. In the context of climate change, the increasing occurrences of extreme meteorological events (in intensity and frequency) are likely to exacerbate the vulnerability of constructions to CSS. Managing the risk associated with CSS thus constitutes a considerable economic challenge.

This PhD subject is part of a research project funded by ADEME (French Agency for Ecological Transition), coordinated by ESTP (https://www.estp.fr/en) and ENPC (https://ecoledesponts.fr/en). The project aims to develop an in-situ soil treatment solution to inhibit the volume change of clayey soils during seasonal wetting-drying cycles. Various actions are planned: laboratory tests, field-scale experiments, and predictive numerical simulations to propose a treatment protocol considering local geological, geotechnical, and meteorological conditions.

Master internship : Microstructural analysis of bio-based granular packing using X-ray microtomography

Stage M2 - 4 to 6 months Publication : 09/10/2024
Biobased materials made from plant particles offer great potential for building insulation, particularly in terms of reducing environmental impact. The aim of the internship is to characterise the 3D microstructure biobased granular packings (sunflower pith particles) through a quantitative analysis of X-ray microtomography images previously obtained at the Synchrotron Soleil. In particular, one objective is to identify relevant microstructural properties that relate to the material's multiphysical performance. Image processing procedures may be based on artificial intelligence techniques (deep learning model). Additional studies on other plants or samples with binders may be carried out using the microtomograph in the laboratory, depending on the progress of the internship.

More information is available in the attached document.

Ph.D.: “Mechanics of swelling clay faults from molecular simulation to earthquakes”

Thèses - 3 years Publication : 01/03/2024
Plate boundary fault zones exhibit a wide range of dynamic behaviors, from aseismic slip to mega-earthquakes. So far, there is no consensus on a model describing the processes controlling these fault behaviors. A possible answer might lie in the properties of smectite, a swelling clay mineral that form the core of many of the fault zones and that is able to adsorb significant amounts of water in-between nanometric minerals. Despite their potential importance, the thermodynamics of hydration/dehydration reactions in smectite and the connections between these reactions and the fault deformations, is not yet known. These fundamental questions are the heart of the ANR project SMEC funding this Ph.D. position. This Ph.D. project focuses on the modeling of part of the SMEC project. More precisely, we propose to combine molecular simulations, granular modeling and micromechanics in order to relate the hydration/dehydration reactions of smectites to the mechanical behavior of faults zones.

PhD Position : Design and fabrication of an inflatable architectured shell at the civil engineering scale

Thèses - 3 years Publication : 08/12/2023
Inflatable structures have many applications in multiple fields such as architecture, entertainment, robotics and more. They can be used for temporary shelters, soft robots, floating devices (pneumatic canoes), furniture (inflatable mattresses), safety equipment (air bags) or medical equipment (cushions, prosthetics). This wide range of applications is motivated by the numerous advantages of this type of structure which are at the same time light, inexpensive, safe and resistant.

PhD Position : Humidity and heat transfers in bio-based buildings

Thèses - 3 years Publication :
Bio-based construction materials are systems containing or formed of vegetal particles, such as wood, hemp, cellulose, flax, cotton, etc., possibly linked with a mineral paste or an organic binder. They represent a promising solution for carbon emission reduction, due to their low production cost and their partial or full recyclability. Moreover, they bring more comfort to the occupants thanks to their moisture-buffering capacity, and they require less energy for heating or cooling. These qualities are obtained through exchanges between water vapor and “bound water”, i.e., water absorbed in the solid structure, combined with heat transfers. Consequently, understanding and predicting water and heat (hygrothermal) transfers in such materials is essential to selecting them appropriately, adjusting their conditions of use, and designing innovative materials. However, the current analysis of their performance is generally based on limited evaluations at a global scale or via macroscopic models lacking physical information.

Post-Doctoral Position : Modelling of fracturing mechanisms in unconsolidated sand reservoirs under fluid injection

CDD - 18 months Publication : 22/09/2023
In hydrocarbons producing fields, Produced Water Re-Injection (PWRI) is known as an economically attractive and environmentally friendly method to manage the produced water. This method has the advantage to maintain the pressure level in the reservoir in order to enhance the hydrocarbon production. However, this technique faces challenges such as the deterioration of the injectivity due to the filtration, around the injection well, of suspended solid particles contained in the produced water. Re-injection in the so-called ‘fracturing regime’ is an option to maintain the injectivity by fracturing the clogged zone formed by the agglomeration of fine particles at the face of the injected formation. However, controlling the injection in the fracturing regime is a key issue for the safety of the production as fracturing should not deteriorate the cap rock integrity. Hydraulic fracturing has been extensively studied for brittle rocks with low permeability and is dominated by tensile failure. However, the mechanisms involved in fracturing of unconsolidated reservoirs which behave as cohesionless granular materials are fundamentally different and are controlled by shear failure, fluidization and induced channelization around the injection point.

Post-Doctoral Position : Physics of water transfers in bio-based materials

CDD - Initial contract for 18 months, extendable to 3 years Publication :
Water transfers in bio-based materials such as wood, plants, paper, hair, natural textiles are essential in our everyday life, but their physics is still poorly known. A specificity of these materials is that they are hygroscopic, i.e., they can absorb, from vapor, a huge amount of water in the form of nanoscale water inclusions between the microfibrils of cellulosic or keratin fibers. This so-called “bound water”, which evaporates in a dry ambient air, is at the origin of the swelling or shrinkage of these materials. Moreover this bound water appears to be very mobile, i.e., it can diffuse throughout the material. The bound water diffusion and its exchanges with free (capillary) water and vapor, are key to the physics of water transfers in such materials, which in turn is key to reducing energy consumption for ventilation and heating, or controlling various processes such as the wetting or drying of such materials.

Internship “Mechanics of swelling clay faults: granular approach”

Stage - 6 months Publication :
Plate boundary fault zones exhibit a wide range of dynamic behaviors, from aseismic slip to mega-earthquakes. So far, there is no consensus on a model describing the processes controlling these fault behaviors. A possible answer might lie in the properties of smectite, a swelling clay mineral that form the core of many of the fault zones and that is able to adsorb significant amounts of water in-between nanometric minerals. Despite their potential importance, the thermodynamics of hydration/dehydration reactions in smectite and the connections between these reactions and the fault deformations, is not yet known. These fundamental questions are the heart of the ANR project SMEC of which this internship is part, and which will focus more specifically on the granular modeling part.