Northwestern Events Calendar

Nov
20
2019

SPREE Seminar: Chloé Arson

When: Wednesday, November 20, 2019
11:00 AM - 12:00 PM CT

Where: Technological Institute, A230, 2145 Sheridan Road, Evanston, IL 60208 map it

Audience: Faculty/Staff - Student - Public - Post Docs/Docs - Graduate Students

Contact: Tierney Acott   (847) 491-3257

Group: McCormick - Civil and Environmental Engineering (CEE)

Category: Lectures & Meetings

Description:

Micro-Macro Damage and Healing Rock Mechanics

 

Abstract
Damage and healing in rocks refer to variations of mechanical and physical properties induced by pore or crack evolution. The gap between microscopic and macroscopic models makes it infeasible to uniquely characterize the pore- and crack- scale mechanisms that control deformation, stiffness variations and strength changes, or to relate the crack rebonding time to the porosity and stiffness healing time. The goal of this research is, therefore, to understand and predict chemo-mechanical damage and healing processes in rocks, by coupling micro-scale thermodynamics to macro-scale poromechanics. Continuum Damage Mechanics allows predicting the evolution of distributions of micro-cracks and the consequent changes of macroscopic mechanical properties. In a reactive environment, crack propagation can be either enhanced or hindered by dissolution/precipitation and mass transport. To understand this interplay, it is possible to define the damage and healing tensors as moments of probability of microstructure descriptors, or to homogenize the behavior of interacting inclusions that characterize the microstructure. In the former approach, the model needs to be informed and calibrated by sequential microstructure images. In the latter approach, it is expected that microscopic balance equations and constitutive laws are known. In both cases, models are validated against macroscopic stress/strain curves and porosity measurements. We restrict this talk to chemo-mechanical damage and healing models based on the homogenization theory.
Chemo-mechanical damage is first studied in granite, in which the expansion of biotite minerals upon weathering is thought to be the cause of spheroidal fractures. At the biotite crystal scale, a time-dependent deformation law is established, based on the kinetics of the predominant chemical reactions. This time-dependent chemical deformation defines the eigenstrain of each biotite inclusion. A Mori-Tanaka homogenization scheme is established to predict the stress induced by biotite expansion in the surrounding matrix. Our simulations suggest the onset of damage occurs earlier under higher biotite abundances and smaller biotite aspect ratios. Biotite orientation, by contrast, exerts a relatively weak influence on damage. Our simulations further show that damage development is strongly influenced by the boundary conditions, with damage initiating earlier under laterally confined boundaries than under unconfined boundaries. Results suggest that relatively minor differences in biotite populations can drive significant differences in the progression of rock weakening.
A self-consistent homogenization model is then formulated to predict long-term chemo-mechanical healing processes induced by pressure solution in salt rock. Hill’s inclusion-matrix interaction law is applied to upscale strains and stresses at the scale of a Representative Elementary Volume. Oedometer tests are simulated for specimens that contain spherical inclusions with uniformly distributed contact plane orientations. It is observed that in samples containing inclusions with different initial void sizes, inclusions with larger pores have a negligible healing rate and are slowing down the overall REV healing process. The healing rate is higher in specimens with smaller grain sizes. For uniform void size distributions, the healing rate increases with initial porosity, but the final porosity change does not depend on the initial porosity.
We conclude the talk by presenting the outline of a unified theory of damage and healing rock poromechanics, in which a homogenization scheme is used to update the Biot coefficient, the Biot modulus and the stiffness tensor upon damage and healing. Pore pressure is assumed to be the eigenstress of each void, and the auxiliary eigenstress of the matrix is introduced to satisfy Levin’s theorem. The modeling approach will allow identifying the conditions in which the coupling between chemical reactions and mechanical stress can be beneficial for geological storage.

Biography
Dr. Chloé Arson is an Associate Professor in the School of Civil and Environmental Engineering at the Georgia Institute of Technology. She earned a Master of Science in soil and rock mechanics (2006) and a Ph.D. in geomechanics (2009) at Ecole des Ponts Paris Tech (France). After being a faculty at Texas A&M University, she joined Georgia Tech in 2012. She teaches Mechanics of Materials, Tunneling and Mining Engineering and Mechanics, and the Finite Element Method for poro-elastic media. Dr. Arson’s areas of expertise and interest are: damage and healing rock mechanics, numerical modeling of multi-scale fracture propagation, micromechanics of particle crushing, underground storage, bio-inspired burrowing mechanics, bio-inspired network dynamics, biomechanics. Dr. Arson regularly gives lectures in Europe and the U.S., organizes sponsored research workshops, serves as a reviewer for over 12 research agencies and more than 30 journals. She chairs the Committee of International Initiatives of the Georgia Tech School of Civil and Environmental Engineering, and leads the NSF funded CEE Gateway to France program, allowing Georgia Tech students to do research internships in French “Grandes Ecoles”. She also chairs Poromechanics Committee of the Engineering Mechanics Institute and she serves as the Associate Editor of the Journal of Rock Mechanics and Rock Engineering and of the ASCE Journal of Engineering Mechanics. Dr. Arson received two PhD research prizes in 2010, the NSF CAREER award in 2016 and the inter-disciplinary research award of Georgia Tech School of Civil and Environmental Engineering in 2017.
He has organized various international conferences and workshops. He is the recipient of numerous prestigious awards and international fellowships including the Alexander von Humboldt Research Prize for Senior Scientists, Max Planck Foundation Research Award for Outstanding Foreign Scientists, Fulbright Senior Scholar Award, Life Achievement Tribology Award, and Institution of Chemical Engineers (UK) Global Award. His research was listed as the top ten science stories of 2015. He is a member of various professional societies, including the International Academy of Engineering (Russia). He has previously worked for various research labs including IBM Almaden Research Center, San Jose, CA. He has held visiting professorship at University of California at Berkeley, University of Cambridge, UK, Technical University Vienna, Austria, University of Paris, Orsay, ETH Zurich, EPFL Lausanne, Univ. of Southampton, UK, Univ. of Kragujevac, Serbia, Tsinghua Univ., China, Harbin Inst., China, and KFUPM, Saudi Arabia.

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