Séminaire IPGS, le 15 septembre à 13h45
Intervenant : Henri Leclere, University of Liverpool
Titre : "Implications of gypsum dehydration on fault mechanics"
Lieu : EOST, 5 rue Descartes, Amphi. Rothé
Résumé :
The effects of dehydration reactions on hydraulic and mechanical properties of rock are analysed to better understand the conditions required to trigger earthquakes. Triaxial experiments are conducted using gypsum and a direct shear sample assembly that allows a constant normal stress to be applied and permeability to be measured during sliding. The evolutions of shear stress, pore-fluid pressure and permeability are continuously measured throughout the experiment until dehydration reaction reached completion. Results show that gypsum dehydration induces transient stable slip weakening that is controlled by pore-fluid pressure and permeability evolutions followed by unstable slip on fully dehydrated product. A microstructural analysis on deformed samples shows clear evidence of dehydration reactions related to the development of Riedel shear structures. A conceptual model is then proposed to explain transient slip weakening during dehydration reactions.