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  • 101.
    Tong, Fuguo
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Zimmerman, Robert W.
    An effective thermal conductivity model of geological porous media for coupled thermo-hydro-mechanical systems with multiphase flow2009Inngår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 46, nr 8, s. 1358-1369Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The objective of this paper is to present the development of an effective thermal conductivity model for simulation of thermo-hydro-mechanical processes of geological porous media. The Wiener bounds and Hashin-Shtrikman bounds for thermal conductivity of three-phase mixture are introduced first, followed by descriptions of thermal conductivities of gas, water and solid, respectively. The derivation of a new effective thermal conductivity model, in closed form, is then presented. The model considers the combined effects of solid mineral composition, temperature, liquid saturation degree, porosity and pressure on the effective thermal conductivity of porous media, when multiphase flow with phase change is involved. The model strictly obeys the Wiener bounds (for anisotropic media) and Hashin-Shtrikman bounds (for isotropic media) over wide ranges of porosities and saturations, and the predicted results agrees very well with the experimental data for MX80 bentonite, compared with Johansen's method. An experimental benchmark test problem under laboratory conditions for coupled thermo-hydro-mechanical processes of compacted FEBEX bentonite is simulated for validation of the model, and the results show that the model provides improved predictions of the evolution and distribution of temperature, with simpler forms of mathematical functions. (C) 2009 Elsevier Ltd. All rights reserved.

  • 102. Tsang, Chin-Fu
    et al.
    Stephansson, Ove
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Kautsky, Fritz
    DECOVALEX Project: from 1992 to 20072009Inngår i: Environmental Geology, ISSN 0943-0105, E-ISSN 1432-0495, Vol. 57, nr 6, s. 1221-1237Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The DECOVALEX project is a unique international research collaboration, initiated in 1992, for advancing the understanding and mathematical modelling of coupled thermo-hydro-mechanical (THM) and thermo-hydro-mechanical-chemical (THMC) processes in geological systems-subjects of importance for performance assessment of radioactive waste repositories in geological formations. From 1992 up to 2007, the project has made important progress and played a key role in the development of numerical modelling of coupled processes in fractured rocks and buffer/backfill materials. The project has been conducted by research teams supported by a large number of radioactive-waste-management organizations and regulatory authorities, including those of Canada, China, Finland, France, Japan, Germany, Spain, Sweden, UK, and the USA. Through this project, in-depth knowledge has been gained of coupled THM and THMC processes associated with nuclear waste repositories, as well as numerical simulation models for their quantitative analysis. The knowledge accumulated from this project, in the form of a large number of research reports and international journal and conference papers in the open literature, has been applied effectively in the implementation and review of national radioactive-waste-management programmes in the participating countries. This paper presents an overview of the project.

  • 103.
    Vesipa, Riccardo
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Zhao, Zhihong
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Estimating Hydraulic Permeability of Fractured Crystalline Rocks Using Geometrical Parameters2010Inngår i: ANALYSIS OF DISCONTINUOUS DEFORMATION: NEW DEVELOPMENTS AND APPLICATIONS / [ed] Ma G; Zhou Y, SINGAPORE: RESEARCH PUBLISHING SERVICES , 2010, s. 685-691Konferansepaper (Fagfellevurdert)
  • 104. Vilarrasa, Victor
    et al.
    Koyama, Tomofumi
    Neretnieks, Ivars
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Shear-Induced Flow Channels in a Single Rock Fracture and Their Effect on Solute Transport2011Inngår i: Transport in Porous Media, ISSN 0169-3913, E-ISSN 1573-1634, Vol. 87, nr 2, s. 503-523Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of mechanical shearing on fluid flow anisotropy and solute transport in rough rock fractures was investigated by numerical modeling. Two facing surfaces of a rock fracture of 194 mm x 194 mm in size were laser scanned to generate their respective digital profiles. Fluid flow through the fracture was simulated using a finite element code that solves the Reynolds equation, while incremental relative movement of the upper surface was maintained numerically to simulate a shearing process without normal loading. The motion of solute particles in a rough fracture undergoing shear was studied using a particle tracking code. We found that shearing introduces anisotropy in fracture transmissivity, with a greatly increased flow rate and particle travel velocity in the direction perpendicular to the shearing direction. Shear-induced channels yield a transport behavior in which advection dominates in the direction parallel with shear and dispersion dominates in the direction perpendicular to shear. The shear-induced flow channels not only increase the flow connectivity, but also the transport connectivity in the direction perpendicular to shear. This finding has an important impact on the interpretation of the results of coupled hydromechanical and tracer transport experiments for measurements of hydraulic and transport properties of rock fractures.

  • 105.
    Zhao, Zhihong
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Stress Effects on Solute Transport in Fractured rocks2011Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The effect of in-situ or redistributed stress on solute transport in fractured rocks is one of the major concerns for many subsurface engineering problems. However, it remains poorly understood due to the difficulties in experiments and numerical modeling. The main aim of this thesis is to systematically investigate the influences of stress on solute transport in fractured rocks, at scales of single fractures and fracture networks, respectively.

    For a single fracture embedded in a porous rock matrix, a closed-form solution was derived for modeling the coupled stress-flow-transport processes without considering damage on the fracture surfaces. Afterwards, a retardation coefficient model was developed to consider the influences of damage of the fracture surfaces during shear processes on the solute sorption. Integrated with particle mechanics models, a numerical procedure was proposed to investigate the effects of gouge generation and microcrack development in the damaged zones of fracture on the solute retardation in single fractures. The results show that fracture aperture changes have a significant influence on the solute concentration distribution and residence time. Under compression, the decreasing matrix porosity can slightly increase the solute concentration. The shear process can increase the solute retardation coefficient by offering more sorption surfaces in the fracture due to gouge generation, microcracking and gouge crushing.

    To study the stress effects on solute transport in fracture systems, a hybrid approach combing the discrete element method for stress-flow simulations and a particle tracking algorithm for solute transport was developed for two-dimensional irregular discrete fracture network models. Advection, hydrodynamic dispersion and matrix diffusion in single fractures were considered. The particle migration paths were tracked first by following the flowing fluid (advection), and then the hydrodynamic dispersion and matrix diffusion were considered using statistic methods. The numerical results show an important impact of stress on the solute transport, by changing the solute residence time, distribution and travel paths. The equivalent dispersion coefficient is scale dependent in an asymptotic or exponential form without stress applied or under isotropic compression conditions. Matrix diffusion plays a dominant role in solute transport when the hydraulic gradient is small.

    Outstanding issues and main scientific achievements are also discussed.

  • 106.
    Zhao, Zhihong
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Jing, Lannu
    Neretnieks, Ivars
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Stress effects on nuclide transport in fractured rocks: A numerical study2010Inngår i: ROCK MECHANICS IN CIVIL AND ENVIRONMENTAL ENGINEERING, 2010, s. 783-786Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The main objective of this study was to investigate the influence of stresses on radioactive nuclide transport in fractured rocks, based on Discrete Element Method (DEM) and a particle tracking approach. Matrix diffusion was also considered in the transport simulation. The results show that stresses not only influence the particle residence time in fracture network, but also change the particle transport paths significantly.

  • 107.
    Zhao, Zhihong
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Neretnieks, Ivars
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Particle mechanics model for the effects of shear on solute retardation coefficient in rock fractures2012Inngår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 52, s. 92-102Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Damage on rock fracture surfaces during shear process changes the mechanical and hydrological properties of the fractures, therefore, affects the solute migration in fractured rocks. Laboratory experiments on this issue are rarely reported in literature due to technical difficulties in measuring the asperity damage and gouge generation. To conceptually investigate the effects of rock fracture surface damage on solute sorption during shear, this paper presents, for the first time, a retardation coefficient model considering the wear impacts and a generic numerical evaluation procedure. The particle mechanics model was employed to investigate the effects of gouge generation (abrasive wear) and microcrack development in the damaged zones, on the solute retardation coefficient in rock fractures. The results from demonstration examples show that the shear process significantly increases the retardation coefficients, by offering more sorption surfaces in the factures due to gouge generation (wear), microcracking and crushing of gouge particles. Conceptually three damage zones are classified to characterize the various wear impacts on the solute transport in single fractures. Outstanding issues of the present model and suggestions for future study are also presented.

  • 108.
    Zhao, Zhihong
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Neretnieks, Ivars
    Shear effects on solute retardation coefficient in rock fractures: Insights from a particle mechanics modelManuskript (preprint) (Annet vitenskapelig)
  • 109.
    Zhao, Zhihong
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Neretnieks, Ivars
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Moreno, Luis
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Analytical solution of coupled stress-flow-transport processes in a single rock fracture2011Inngår i: Computers & Geosciences, ISSN 0098-3004, E-ISSN 1873-7803, Vol. 37, nr 9, s. 1437-1449Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A closed-form solution is presented for modeling the coupled stress-flow-transport processes along a single fracture embedded in a porous rock matrix. Necessary assumptions were made to simplify the subject into a two-dimensional (2D) problem, considering the changes of fracture aperture and matrix porosity under various stress conditions. The cubic law was assumed to be valid for the fluid flow in the fracture, with an impermeable rock matrix. For transport mechanisms, advective transport along the fracture, longitudinal hydrodynamic dispersion in the flow direction, and the matrix diffusion were considered in three different transport models under constant concentration or constant flux (Danck- werts’) inlet boundary conditions. This analytical solution can be used as a constitutive model, or as an example for validation of similar constitutive models, for modeling the coupled hydro-mechanical- chemical (HMC) processes in fracture networks of crystalline rocks. The influences of stress/deformation processes on different transport mechanisms in a single fracture under different inlet boundary conditions were studied for the first time. The results show that changes of fracture, as controlled by a combination of normal closure and shear dilatancy, have a significant influence on the solute concentration distribution both along the fracture and in the rock matrix, as well as on the solute residence/breakthrough time, especially when shear-induced dilatancy occurs. Under compressions, the decreasing matrix porosity slightly increases the solute concentration along the fracture and in the rock matrix.

  • 110.
    Zhao, Zhihong
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Jing, Lanru
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Neretnieks, Ivars
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Moreno, Luis
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk apparatteknik.
    Numerical modeling of stress effects on solute transport in fractured rocks2011Inngår i: Computers and geotechnics, ISSN 0266-352X, E-ISSN 1873-7633, Vol. 38, nr 2, s. 113-126Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effects of stress/deformation on fluid flow and contaminant transport in fractured rocks is one of the major concerns for performance and safety assessments of many subsurface engineering problems, especially radioactive waste disposal and oil/gas reservoir fields. However, very little progress has been made to study this issue due to difficulties in both experiments and numerical modeling. The objective of this study is to systematically investigate the influence of stress on solute transport in fractured rocks for the first time, considering different stress and hydraulic pressure conditions. A hybrid approach combining discrete element method (DEM) for stress-flow simulations and a particle tracking algorithm is developed. The impact of matrix diffusion (diffusion of molecular size solutes in and out of the rock matrix, and sorption onto the surface of micropores in rock matrix) is also included. The numerical results show that stress not only significantly changes the solute residence time through the fracture networks, but also changes the solute travel paths. Matrix diffusion plays a dominant role in solute transport when the hydraulic gradient is small, which is often encountered in practice.

  • 111.
    Zimmerman, Robert W.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630), Teknisk geologi och geofysik.
    The Imperial College lectures in petroleum engineering2018Collection/Antologi (Annet vitenskapelig)
    Abstract [en]

    This book presents, in a self-contained form, the equations of fluid flow in porous media, with a focus on topics and issues that are relevant to petroleum reservoir engineering. No prior knowledge of the field is assumed on the part of the reader, and particular care is given to careful mathematical and conceptual development of the governing equations, and solutions for important reservoir flow problems. Fluid Flow in Porous Media starts with a discussion of permeability and Darcy's law, then moves on to a careful derivation of the pressure diffusion equation. Solutions are developed and discussed for flow to a vertical well in an infinite reservoir, in reservoirs containing faults, in bounded reservoirs, and to hydraulically fractured wells. Special topics such as the dual-porosity model for fractured reservoirs, and fluid flow in gas reservoirs, are also covered. The book includes twenty problems, along with detailed solutions. As part of the Imperial College Lectures in Petroleum Engineering, and based on a lecture series on the same topic, this book provides the introductory information needed for students of the petroleum engineering and hydrology.

  • 112.
    Zimmerman, Robert W.
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630), Teknisk geologi och geofysik.
    Lutz, M.P
    Thermal and electrical conductivity of composites with graded interfaces2006Inngår i: International Journal of Advances in Science and Technology, ISSN 2229-5216, Vol. 45, s. 1097-1102Artikkel i tidsskrift (Fagfellevurdert)
  • 113.
    Zywna, Michal
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik, Teknisk geologi och geofysik.
    Analysis of Lining Properties at Landfills Using Geophysical Methods - Case Study: Tveta (Sweden).2011Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Recently established EU environmental legislation obliged Sweden to close many landfills until year 2020. Such an operation requires a lot of inexpensive and water resistant coverage materials. Six prototypes of linings were constructed at Tveta landfill. Built coverage consisted mainly of residual products such as compost, sludge, fly and bottom ash. Between 2004 and 2007 water permeability through tested coverage was well below the maximum limit for non-hazardous waste. However, recent lysimeter records indicated increased permeability through the constructed linings. Readings of water infiltration were verified. Direct current (DC) resistivity, induced polarization (IP) and ground penetrating radar (GPR) were the methods applied in the research. The data was processed to present resistivity distribution in 2D pseudo-sections and 3D model. Resistivity measurements confirmed increased conductivity at the area with highest lysimeter readings. Unfortunately, GPR and IP output could not be used as reference information for DC resistivity readings. Constructed prototypes seemed to be suitable for coverage lining. Leakage was probably a result of minor mass transport along the slopes of the waste pile. It was recommended to prepare additional DC resistivity measurements to verify correctness of the processed 2D pseudo-sections and 3D model.

123 101 - 113 of 113
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