Cracking the Rock Mechanisms with the European Synchrotron Experimental Fleet.

Despite daily progress over half a century, rock deformation leaves significant challenges in understanding their underlying mechanics and providing accurate models. Experimental geologists developed various approaches to deform rock samples, but coupling them with X-ray tomography marked a turn in monitoring failure precursors and interpreting stress-strain curves. X-ray transparent triaxial presses become more advanced and equipped yearly, allowing the complete rheological study of earth material. 

The European Synchrotron Radiation Facility is the unique 4th generation synchrotron worldwide. Its Extremely Brilliant Source (EBS) allows the scan of samples encapsulated in thick autoclaves at high speed. It proposes a state-of-the-art fleet of triaxial presses capable of accurately measuring and observing the deformation of a rock sample while passively recording its acoustic emissions. It enables researchers to analyse fault movements, stress transfer, and energy release mechanisms at different sample sizes while precisely controlling stress, temperature, and deformation rates.

With comprehensive data analysis, such as crack segmentation and digital volume correlation coupled with acoustic events' time and spatial resolution, it is now possible to identify failure precursors at high spatial (X-rays) and soon temporal (acoustic) resolutions. One may also investigate phenomena with low amplitude or high frequency, which produce deformation but appear aseismic.

Here, we present the successful results of several teams that have used these devices and their latest technical developments.