Damage induced by precipitation in saturated porous limestone
Résumé
One century ago, Stephen Taber mentioned that the crystallisation pressure could play a role in geological settings, but to now no experimental data could really prove it in a clear way [1]. Our goal is to come up with an experiment that clearly demonstrate the potential of crystallisation pressure as a fracture inducer in geological settings.
Data on the salt precipitation and distribution in the pore space of a confined and saturated limestone sample are presented, as well as the damaging character of this precipitation. For this purpose, two different experiments were designed and set up. The first one focuses on the precipitation of barite studied in a system involving the contra diffusion of Ba2+ and SO42- rich solutions in a cylindrical sample of Lavoux limestone. The second one aims at creating a localised mirabilite precipitation front in the same type of cylindrical Lavoux specimen. To that extent, cooling cycles are imposed on the sample saturated with an aqueous Na2SO4 solution. The experiments are monitored with video acquisition and temperature sensors to measure sample swelling or temperature change due to crystallisation. The post treatment consists in 3D X-ray micro-tomographic scans of the damaged sample conducted at the UPPA Centre for X-ray Imaging DMEX together with thin sections of relevant features. Depending on the first results, we may show additional data of experiments monitored with an acoustic set up in order to listen to the acoustic emission created by crystallisation and fracturing events. This allows localizing the cracks epicenter and the damage zone.