Diffuse transport in clay media: µm to nm scale characterization of pore space and mineral spatial organization

In the framework of radioactive waste repository, clayrock formations are foreseen as barrier materials due to their diffusion properties. In clay materials, the dominant transport mode is diffusive and depends mainly on various parameters such as the mobility of the species in water, the accessible porosity, the pore space geometry and the retardation as a result of reactions such as sorption or ion exchange (Tournassat and Appelo, 2011). In this way, the European CATCLAY project (EURATOM FP7), in the context with research on transport in porous materials, was proposed to describe the cation migration processes in natural clayrocks. The project is structured along 3 RTD workpackages, combining modeling and experimental studies from a simpler, analogous system (monophasic compacted clay system) to clayrocks (Callovo-Oxfordian argillites, Opalinus Clay and Boom Clay). Part of this experimental studies focuses on small scale structure (µm - nm) property of rocks in order to determine how the spatial distribution of mineral and pores at small scales can influence diffusion driven transport of sorbing cations. The present study focuses on compacted illite properties (simpler analogous system) in hopes to extent this study to the natural clayrock formation. Illite was chosen by the way that is the main constituent of clayrock. Compacted illite material represents thus an analogy with the clay matrix constituting clay-rocks. Our approach is mainly based on imaging the small scale structural organization of compacted illite material and analyzing the obtained images in order to extract information on pore space and mineral spatial distribution. Techniques for imaging the texture of illite material like water saturated, in compacted state, were first developed. The first step was to improve classic resin impregnation method in order to preserve the texture without losing the clay confinement and modifying the pore space geometry. This has been done by taking into account the molecule size of the monomer, the low viscosity, the dipole moment (adapted for the clayrock with swelling clay content) and the controlled time polymerization. MMA monomer proved to be the most suitable resin in our study. The small scale structure of impregnated sample was then imaged in 2D using Transmission Electron Microscopy (TEM) and in 3D using Focused Ion Beam coupled to Scanning Electron Microscopy (FIB/SEM). For TEM observations, a set of ultra-thin serial sections (50 - 100 nm) were cut using a microtome. A set of 2D images were then acquired using a resolution ranged between 100 nm and 10 Å. TEM images clearly show us the multi-scale organization of clay materials (Figure 1 and 2); we observe the 10 Å spacing sheets constituting the illite particles, nanometer size illite clay particles more or less aggregated and the surrounding pores having a size ranging from few hundred nanometers to nanometer. FIB/SEM analysis is currently in progress. From FIB/SEM, a set of serial images can be acquired using the "slice and view" method (Keller et al., 2011). Then, 2D FIB/SEM images need to be aligned to reconstruct a 3D volume. Image resolution is limited to 10-20 nm. Both methodologies (FIB-tomography and TEM techniques) are thus complementary method for the up-scaling characterization of the structural organization of compacted clayey materials. TEM images analysis allow to scale down the resolution size since only a part of the pore space could thus be imaged with FIB/SEM method (Keller et al., 2011). Viewing and performing a qualitative description of images constitute a major result and can help us to better understand how the transfer pathways and retention sites are organized in the porous media. Thanks to image analysis method, pores and minerals can be thresholded from grey level TEM and FIB/SEM images. Quantitative parameters can be then computed based from segmented images. In this objective, we currently focus our analysis in order to determine the size and the morphology of pores, the main geometrical features of clay particles (number of layers, size, shape...), the spatial distribution of clay particles (individual/aggregates, type of contact between the clay particles, orientation...) and the pores connectivity. Quantitative parameters are expected to be used in various transfer modeling approaches. This will be done in the framework of SIMISOL project which is focused on the modeling cation diffusion from atomic to nanometer scales

Diffusion as the main process for mass transport in very low water content argillites: 1. Chloride as a natural tracer for mass transport—Diffusion coefficient and concentration measurements in interstitial water

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95672/1/wrcr9815.pd

Diffusion as the main process for mass transport in very low water content argillites: 2. Fluid flow and mass transport modeling

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94838/1/wrcr9843.pd

Cage-based Tracking for Performance Animation

International audienceFull body performance capture is a promising emerging technology that has been intensively studied in Computer Graphics and Computer Vision over the last decade. Highly-detailed performance animations are easier to obtain using existing multiple views platforms, markerless capture and 3D laser scanner. In this paper, we investigate the feasibility of extracting optimal reduced animation parameters without requiring an underlying rigid kinematic structure. This paper explores the potential of introducing harmonic cage-based linear estimation and deformation as post-process of current performance capture techniques used in 3D time-varying scene capture technology. We propose the first algorithm for performing cage-based tracking across time for vision and virtual reality applications. The main advantages of our novel approach are its linear single pass estimation of the desired surface, easy-to-reuse output cage sequences and reduction in storage size of animations. Our results show that estimated parameters allow a sufficient silhouette-consistent generation of the enclosed mesh under sparse frame-to-frame animation constraints and large deformation

Conversion of Performance Mesh Animation into Cage-based Animation

International audienceMarkerless highly-detailed performance capture is an emerging technology in vision-based graphics and 3D video. For instance, a framework for generating mesh animations from multi-view silhouettes is presented in [Vlasic et al. 2008]. Achieving inverse animation by approximating dynamic mesh using rigid skinning has inspired researchers to convert video-based reconstructed mesh sequence into rigid kinematic parameters as seen in [de Aguiar et al. 2008]. In contrast with previous techniques using skeleton- based animation paradigms, we describe an efficient linear estimation framework to convert non-rigid performance animation into cage-based animation. Our approach retrieves animation parameters through a single-pass minimization process without the need of an underlying rigid kinematic structure

CageIK: Dual-Laplacian Cage-Based Inverse Kinematics

International audienceCage-based deformation techniques are widely used to con-trol the deformation of an enclosed fine-detail mesh. Achieving deforma-tion based on vertex constraints has been extensively studied for the case of pure meshes, but few works specifically examine how such vertex con-straints can be used to efficiently deform the template and estimate the corresponding cage pose. In this paper, we show that this can be achieved very efficiently with two contributions: (1) we provide a linear estima-tion framework for cage vertex coordinates; (2) the regularization of the deformation is expressed on the cage vertices rather than the enclosed mesh, yielding a computationally efficient solution which fully benefits from cage-based parameterizations. We demonstrate the practical use of this scheme for two applications: animation edition from sparse screen-space user-specified constraints, and automatic cage extraction from a sequence of meshes, for animation re-edition

Capturer la géométrie dynamique vivante dans les cages

Reconstruire, synthétiser, analyser et réutiliser les formes dynamiques capturées depuis le monde en mouvement est un défi récent qui reste encore en suspens. Dans cette thèse, nous abordons le problème de l'extraction, l'acquisition et la réutilisation d'une paramétrisation non-rigide pour l'animation basée vidéo. L'objectif principal étant de préserver les propriétés globales et locales de la surface capturée sans squelette articulé, grâce à un nombre limité de paramètres contrôlables, flexibles et réutilisables. Pour résoudre ce problème, nous nous appuyons sur une réduction de dimensions détachée de la surface reposant sur le paradigme de la représentation par cage. En conséquence, nous démontrons la force d'un sous-espace de la forme d'une cage géométrique pour encoder des surfaces fortement non-rigides.Reconstructing, synthesizing, analyzing to re-using dynamic shapes that are captured from the real-world in motion isa recent and outstanding challenge. Nowadays, highly-detailed animations of live-actor performances are increasinglyeasier to acquire and 3D Video has reached considerable attention in visual media production. In this thesis, we addressthe problem of extracting or acquiring and then reusing non-rigid parametrization for video-based animations. At firstsight, a crucial challenge is to reproduce plausible boneless deformations while preserving global and local capturedproperties of the surface with a limited number of controllable, flexible and reusable parameters. To solve this challenge,we directly rely on a skin-detached dimension reduction thanks to the well-known cage-based paradigm. Indeed, to thebest of our knowledge, this dissertation opens the field of cage-based performance capture. First, we achieve ScalableInverse Cage-based Modeling by transposing the inverse kinematics paradigm on surfaces. To do this, we introduce acage inversion process with user-specified screen-space constraints. Secondly, we convert non-rigid animated surfacesinto a sequence of estimated optimal cage parameters via a process of Cage-based Animation Conversion. Building onthis reskinning procedure, we also develop a well-formed Animation Cartoonization algorithm for multi-view data in termof cage-based surface exaggeration and video-based appearance stylization. Thirdly, motivated by the relaxation of priorknowledge on the data, we propose a promising unsupervised approach to perform Iterative Cage-based GeometricRegistration. This novel registration scheme deals with reconstructed target point clouds obtained from multi-view videorecording, in conjunction with a static and wrinkled template mesh. Above all, we demonstrate the strength of cage-basedsubspaces in order to reparametrize highly non-rigid dynamic surfaces, without the need of secondary deformations. Inaddition, we state and discuss conclusions and several limitations of our cage-based strategies applied to life-like dynamicsurfaces, captured for vision-oriented applications. Finally, a variety of potential directions and open suggestions for furtherwork are outlined.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Desaturation and structures relationships around drifts excavated in the well-compacted Tournemire's argillite and their impact on the hydraulic head profiles

International audienceThis study aimed to explore the relationships between the rock desaturation and the EDZ extension subsequent to the excavation of a century-old tunnel and recent drifts (1996 and 2003) at the Tournemire Underground Research Laboratory. The other objective of this work was to assess the impact of this desaturation on the hydraulic head profile measured around the tunnel. One section was selected per drift. Two boreholes were realized for each section: parallel and inclined (45°) with respect to the bedding. For each borehole, we performed on-site drill core mapping, petrophysical measurements and pneumatic and hydraulic tests by means of a Modular Mini-Packer System (MMPS) device. Results indicate that EDZ around drifts is mainly a combination of unloading joints, mimicking the drift shape, and of desaturation cracks, parallel to the bedding. The EDZ extension around the tunnel is twice to three times that of drifts 1996 and 2003 and essentially composed of unloading joints resulting from the mechanical response of the rock. The masonery covering the tunnel walls is assumed to have protected the rock from the seasonal variations of the air humidity, thus limiting (without excluding) the formation of desaturation cracks. The EDZ extension deduced from core mapping is in agreement with that deduced from pneumatic tests with permeabilities several orders of magnitude greater than in the undisturbed zone. Degrees of saturation for the three sections range between 0.9 and 1 in the EDZ area and reach 1 in the undamaged zone. The head profile deduced from measurements recorded since 2002 indicates the occurrence of sub-atmospheric water pressures with an extension of ca 40m around the tunnel. We have searched to quantify the impact of the tunnel since its excavation on the degrees of saturation and the hydraulic heads. The simulation was performed by considering, as a first approach, the absence of fracturation in the EDZ area. A constant suction of -3300m, deduced from the mean annual values of relative humidity and temperature measured in the tunnel atmosphere since 2002, was applied at the tunnel wall. The degrees of saturation simulated around the tunnel are underestimated in the EDZ area and consistent to experimental data in the unfractured zone. The modelling of hydraulic heads is quite consistent to experimental values in the vertical direction and overestimated in the horizontal direction. This study has demonstrated the role played by fracturation on the distribution of petrophysical parameters and of heads around drifts and the century-old tunnel. It has also demonstrated the necessity of coupling mechanic and hydraulic calculations by considering capillary forces

Effect of Water Saturation on the Diffusion/Adsorption of 22Na and Cesium onto the Callovo-Oxfordian Claystones

The diffusion and adsorption behaviors of sodium and cesium were investigated in the Callovo-Oxfordian claystones (France) under unsaturated conditions. Through-, out-, and in-diffusion laboratory experiments were performed on intact and compacted samples. These samples were partially saturated using an osmotic method for imposed suction up to 9 MPa. This specific technique enabled us to obtain water saturation degree ranging from 81% to 100% for intact samples and from 70% to 100% for compacted materials. The results showed a very low impact of water saturation on the extent of adsorption for 22Na and cesium, onto intact and compacted materials. Such observations suggest that the saturation degrees were not low enough to limit the access of cations to adsorption sites on clay surfaces. At full saturation, enhanced diffusion for 22Na and cesium was clearly evidenced onto intact and compacted samples. Under unsaturated conditions, the diffusion behavior for Cs and 22Na was not only slower but also distinct as compared to fully saturated samples. For the intact rock and under suction of 1.9 MPa, the Cs diffusivity was reduced by a factor of 17, whereas for sodium, it was reduced by a factor of 5. Explanation was then proposed to explain such a difference