Tournassat / Bergaya Natural and Engineered Clay Barriers

1. Auflage 2015
ISBN: 978-0-08-100050-2
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, Band Volume 6, 446 Seiten

Reihe: Developments in Clay Science

Clays are used as barriers for the isolation of landfills and contaminated sites. They are envisioned as long-term storage media for hazardous materials and radioactive wastes, and as seals in the case of geological CO2 sequestration or energy storage. Clay properties greatly influence the integrity, efficiency, and safety of these applications.  Natural and Engineered Clay Barriers provides a clear view of the fundamental properties of clay materials and how these properties affect their engineering applications. This volume focuses on how the mass transfer properties (hydraulic permeability, gas fluxes, molecular diffusion, semi-permeable membrane properties), geochemical reactivity (adsorption, dissolution) and mechanical properties of clay barriers at the macroscale are influenced by phenomena that occur at clay mineral - water interfaces. - Examines clay properties from the molecular to the macroscopic scale - Addresses experimental and modeling issues - Authored by experts in the properties of clay barriers

Autoren/Hrsg.

Tournassat, Christophe

Bergaya, Faïza

Leseproben

Introduction
Christophe Tournassata,b, Carl I. Steefelb, Ian C. Bourgb,c and Faïza Bergayad     aWater, Environment and Ecotechnology Division, French Geological Survey (BRGM), Orléans, France     bEarth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA     cDepartment of Civil and Environmental Engineering, Princeton University, Princeton, NJ, USA     dCentre de Recherche sur la Matière Divisée, Centre National de la Recherche Scientifique (CNRS), Orléans, France In recent years, the scientific community has seen a remarkable surge of interest in the properties of clays as they apply in a variety of natural and engineered settings. In part, this renewed interest is traceable to the very property that, in the past, had relegated clay-rocks to a minor status in hydrology, namely their low hydraulic conductivity. While clay-rocks might be largely bypassed by contaminant plumes in groundwater aquifers and by saline fluids in sedimentary basins, their low permeability allows them to play key roles in several important subsurface energy-related applications, including the long-term storage of nuclear wastes in geologic repositories and CO2 sequestration in subsurface geologic formations. In these applications, the low transmissivity of clay-rich geologic formations or engineered clay barriers provides at least part of the basis for isolation of radionuclide contaminants and CO2 from the biosphere. Clay materials are an important part of the multibarrier systems for nuclear waste storage under consideration worldwide, but their performance must be demonstrated on the timescale of hundreds to thousands of years (Altmann, 2008; Busch et al., 2008; Chapman and Hooper, 2012; Armitage et al., 2013; Neuzil, 2013). The low permeability of clay-rich shales also explains why hydrocarbon resources are not easily exploited from these formations, thus requiring in many cases special procedures such as hydraulic fracturing in order to extract them. In addition to their low permeability, clay minerals have other properties of interest in these applications, including their very high adsorption capacity (Chapter 2, in this volume). The strong adsorption and resulting retardation of many contaminants by clay minerals make them ideal for use in natural or engineered barrier systems, particularly where there is a desire to improve confidence in the safety of waste isolation beyond reliance on slower transport rates alone. In addition, the high pH/redox buffering capacity (Chapter 3, in this volume) and slow dissolution kinetics of clay minerals (Chapter 4, in this volume), along with the slow diffusive mass transport in clay-rich media (Chapter 6, in this volume), make clay-rocks and engineered clay barriers remarkably stable under the chemical perturbations generated by high partial pressure of CO2 or by the presence of concrete, steel, and other exogenous materials (Chapter 5, in this volume). While clay materials offer some striking benefits in these and other applications, their properties and behavior under relevant conditions remain only partly understood. With the exception of the work by Bredehoft and Papadopolous (1980), Bredehoft et al. (1983), and Neuzil (1982, 1986, 1993, 1994), the hydrodynamics of clay-rocks had, until these last two decades, attracted only limited attention from hydrogeologists. As discussed by Neuzil (2013), flow through clay-rich formations may not be adequately described by Darcy's Law. In fact, engineered clay barriers and clay-rocks show a remarkable array of macroscale properties such as high swelling pressure, very low permeability, semipermeable membrane properties, and a strong coupling between geochemical, mechanical, and osmotic properties (Malusis et al., 2003; Malusis and Shackelford, 2004). These properties are thought to arise from the distinct geochemical, transport, and mechanical properties of the interlayer (nano)pores of swelling clay minerals such as Na+-montmorillonite and other smectites (Chapters 8–10, in this volume). Clay-rocks typically show a nonlinear dependence of the flow field on the pore pressure, particularly at low pressure gradients and flow rates where threshold behavior prevails. Much of this anomalous behavior is traceable to chemical, electrical potential, and thermal gradients that result in nonconjugate driving forces for hydrodynamic flow and molecular diffusion. The prediction of gas migration through clay barriers (e.g., CO2 from carbon sequestration storage, or H2 generated by radiolysis or corrosion of steel containers) is a difficult challenge as well because of the complex interplay of the gas transport processes with the mechanical properties and the pore structure of clay-rocks (Chapter 7, in this volume). Even where hydrodynamic flow through clay-rocks is limited or suppressed altogether, diffusion offers another possible means for transport that must be evaluated. This task is rendered difficult by the incomplete understanding of the microstructure and surface electrostatics of clay-rich materials, such that multiple models exist with very different underlying concepts/hypotheses on the diffusion and semipermeable properties of the clay nanopores (Chapter 6, in this volume). The development of predictive mesoscale models of water, gas, and solute mass fluxes in nanoporous media is in fact a long-standing challenge in the geosciences. The behavior of nanoporous clay environments is complicated by the fact that the pore structure of clay materials is heterogeneous, such that water and ions can be present in bulk-liquid-like water, on external surfaces of clay particles, and in nano-scale confinement in clay interlayers (Chapter 1, in this volume). To understand and predict the coupling phenomena, it is often necessary to examine the physical processes at the pore scale, upscale the physical laws to the continuum scale, and compare continuum scale model predictions to geophysical or other macroscopic observables. A range of upscaling strategies has been developed to predict the various properties of interest for clay materials (Chapters 8–11, in this volume). This volume opens on the surface and chemical properties of clay minerals and clay barriers (Chapters 1–4). Then, it focuses on mass fluxes through clay barriers (Chapters 5–7) and on coupled thermo–hydro–mechanical processes (Chapters 8 and 9). The end of the volume is focused on upscaling modeling strategies and their applications (Chapters 10 and 11). A large part of the current understanding of clay barrier properties has been gained through studies conducted on radioactive waste storage systems, a fact that is reflected in most of the chapters. However, the recent breakthroughs in the field and the challenges that remain are not limited to this application. For instance, the development of recovery techniques for gas and light liquid hydrocarbons from shale has created a new series of challenges for the clay scientist community. Hopefully, this volume can provide a solid basis to the clay and nonclay scientist communities for the identification of current understanding, recent breakthroughs, and the challenges that remain in the field of clay barriers. Note on Terminology and Abbreviations
For the purpose of consistency of clay terminology, the abbreviations used in all chapters of this volume follow the terminology of the Handbook of Clay Science (Bergaya and Lagaly, 2013). The most used abbreviations are Bent for bentonite, Sm for smectite, Mt for montmorillonite, Kaol for kaolinite, and I-Sm for illite-smectite, the clays and clay minerals most frequently encountered in clay barriers. References
Altmann S. Geo'chemical research: a key building block for nuclear waste disposal safety cases. J. Contam. Hydrol. 2008;102:174–179. Armitage P, Faulkner D, Worden R. Caprock corrosion. Nat. Geosci. 2013;6:79–80. Bergaya F, Lagaly G. Handbook of Clay Science Developments in Clay Science. second ed. Elsevier; 2013. Bredehoeft J.D, Papadopulos S.S. A method for determining the hydraulic properties of tight formations. Water Resour. Res. 1980;16:233–238. Bredehoeft J, Neuzil C, Milly P. Regional Flow in the Dakota Aquifer: A Study of the Role of Confining Layers US Geological Survey Water Supply Papers 2237. 1983 p. 45. Busch A, Alles S, Gensterblum Y, Prinz D, Dewhurst D.N, Raven M.D, Stanjek H, Krooss B.M. Carbon dioxide storage potential of shales. Int. J. Greenhouse Gas Control. 2008;2:297–308. Chapman N, Hooper A. The disposal of radioactive wastes underground. Proc. Geol. Assoc. 2012;123:46–63. Malusis M.A, Shackelford C.D, Olsen H.W. Flow and transport through clay membrane barriers. Eng. Geol. 2003;70:235–248. Malusis M.A, Shackelford C.D. Predicting solute flux through a clay membrane...