17th Annual C. W. Lovell Distinguished Lecture
4:30 p.m., Friday, November 1, 2019
Lawson Hall, Room 1142, Purdue University
Professor Cino Viggiani
University of Grenoble Alpes
"3D experimental geomechanics at the grain scale: what for?"
With x-ray micro tomography it is now possible to acquire 3D full-field measurements of granular materials at suitable resolutions. Digital Image Correlation has been used to determine the distribution of strain in a specimen and/or individual grain kinematics, i.e., displacements and rotations of individual grains. These works have provided a deep insight into the micro-mechanics of the processes governing the behavior of granular materials.
This lecture will present recent advances in experimental micro (geo)mechanics achieved thanks to x-ray tomography and digital image analysis. In particular, we will focus on some recent experimental measurements of a 3D fabric tensor and its evolution during shearing of granular materials. Triaxialcompression experiments on natural sands are chosen to investigate the evolution of fabric. Two different subsets of the specimen are chosen for the contact fabric analysis: one inside and another one outside a shear band. Individual contact orientations are measured using advanced image analysis approaches within these subsets. Fabric is then statistically captured using a second order tensor and the evolution of its anisotropy is related to the macroscopic behaviour.
Finally, some very recent results obtained on fabric evolution from triaxialcompression of lentils (i.e., very anisotropic grains!) are also presented. More generally, the lecture will try to convey the following two messages: 1) to convince the audience that x-ray imaging is a measurement tool, not only a way to provide fancy images, and 2) to discuss what sort of modeling applications these rather exotic data can help to inform or inspire.
About Professor Cino Viggiani
Cino Viggiani was born in Napoli (Italy) and is now Full Professor of Geomechanics and Civil Engineering at the University of Grenoble Alpes, which he first joined back in 1995 as a Marie Curie Post-Doctoral Research Fellow. In 2012, he was promoted to Professor of Outstanding Rank by the French National Council of Universities. He served as vice-president for research in Physics and Engineering at the University of Grenoble Alpes, as well as head of the research unit Laboratoire 3SR in Grenoble. His research involves experimental investigations as well as theoretical and numerical modelling of the behavior of geomaterials, including localized failure and hydro-mechanical coupling. Applications are principally in geoenvironmental, petroleum, and civil engineering. On the experimental side, he has been developing and using quite a range of innovative soil and rock testing apparatus and experimental techniques – in particular, Digital Image Correlation, x-ray tomography, and neutrontomography. He has delivered about 30 Keynote lectures worldwide and he is author of over 200 scientific papers, including 90 peer-reviewed Journal papers and about 150 refereed publications in Books, International Workshops and Conferences. He was a founding editor of the International Journals Acta Geotechnica and Open Geomechanics and is currently President of ALERT-Geomaterials.