Geomechanics: David Grégoire
Dr. David Grégoire (HDR) graduated from the ENS Cachan in 2004. He then obtained his PhD in Mechanics from INSA-Lyon (2008) and joined Northwestern University (USA) as a postdoctoral research associate. A year later, he returned to France for a second postdoctoral position at UPPA where he was finally hired in 2010 on a tenure track position (Ass. Pr.) associated with a CNRS / Higher Education chair for five years on geomechanics. This chair allowed him to boost his early carrier with a reduced teaching load and a specific grant for building new research projects.
The geomechanics chair is focused on porous materials and particularly on the multi-physics couplings appearing at the small scale, but with significant consequences at the large scale of a structure or a reservoir. This encompasses damage, failure and transport couplings in mesoporous materials and adsorption-induced swelling in microporous materials. Experimental tests, modelling and numerical simulations have been performed to characterise materials, to build databases, to enhance existing models and propose new ones, to validate and compare results at the material scale and the structural scale.
Several advances have been obtained in multidisciplinary domains. A unique experimental database of fracture tests investigating size effect and boundary effect has been built. This database was then used to demonstrate that a lattice-based approach is capable of capturing the global and the local failure processes of quasi-brittle materials, whereas a classical continuum nonlocal approach fails. This lattice-based approach has then been enriched to study failure and transport couplings. The interactions of a propagating crack, stimulated by fluid injection, with an existing network of natural joint, have been studied and experimental comparisons have been performed. Gas molecule transport through a damageable porous media has been also studied. A new strategy has been proposed to estimate directly, and without any fitting parameters, the intrinsic and the apparent permeability of a mesoporous material, based only on the measurement of its pore size distribution by mercury intrusion. The interactions of the fluid molecules and the pore walls are taken into account and the experimental Klinkenberg’s law is recovered. At a lower scale, down to the nanometric size of a pore, fluid/structure interactions and fluid confinement effects have been properly upscaled through enhanced poromechanics to predict adsorption-induced swelling in microporous materials.
During this five years period, David Grégoire published 18 articles, two book chapters and he disseminated his results at 50 conferences. He also supervised five PhD students, three postdocs and was involved in 19 public and private projects including eleven as the principal investigator. He was defended his Habilitation Thesis in 2014 and after the end of this chair, he took the lead of his research team (Geomechanics and porous media – 19 people). David Grégoire is a member of two EMI committees and is an HCERES expert. He was awarded twice nationally and twice internationally and has organised four conferences.