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Vladimir Cvetkovic - One of the best experts on this subject based on the ideXlab platform.

  • A High-Resolution Contact Analysis of Rough-Walled Crystalline Rock Fractures Subject to Normal Stress
    Rock Mechanics and Rock Engineering, 2019
    Co-Authors: Bo Li, Yangyang Mo, Vladimir Cvetkovic
    Abstract:

    Analysis of Rock fracture deformation by normal stress is important for quantifying hydromechanical properties of fractured Rocks that are related to a large number of geophysical problems and geoengineering applications. Experimental and numerical results for the closure of Crystalline Rock fractures subject to normal stress are presented in this study. An efficient high-resolution, half-space elastic–plastic contact model for analyzing the closure of Crystalline Rock fractures based on the Boussinesq’s solution is validated by high-precision and high-resolution experimental data. Using the validated elastic–plastic model, we investigate the correlation between fracture-specific stiffness and multi-scale surface roughness. The wavelet analysis method and the extended averaged slope magnitude for asperity heights (referred to as \( Z_{2}^{{3{\text{D}}}} \)) are introduced to characterize the multi-scale surface roughness. The results show that the elastic–plastic contact model is effective and precise in modeling the closure of Crystalline Rock fractures, which matches better with the test results than the elastic model. The multi-scale features of surface roughness can be well characterized by the wavelet analysis and the extended roughness parameter \( Z_{2}^{{3{\text{D}}}} \). The specific stiffness is nonlinearly correlated with the multi-scale surface roughness that possibly follows a power law. The validated elastic–plastic contact model and the multi-scale surface roughness characterization methods, as well as the nonlinear correlation between the specific stiffness and the multi-scale surface roughness presented in this study, are helpful for evaluating the dependence of mechanical behaviors of Rock fractures on its multi-scale surface roughness.

  • Evaluation of single-well injection-withdrawal tests in Swedish Crystalline Rock using the Lagrangian travel time approach
    Water Resources Research, 2011
    Co-Authors: Vladimir Cvetkovic, Hua Cheng
    Abstract:

    A series of 10 single-well injection-withdrawal (SWIW) tests are evaluated with two tracers each: uranine and cesium (Cs). An evaluation tool for SWIW tests in Crystalline Rock is presented on the ...

  • inference of field scale fracture transmissivities in Crystalline Rock using flow log measurements
    Water Resources Research, 2010
    Co-Authors: Andrew Frampton, Vladimir Cvetkovic
    Abstract:

    Inference of field-scale fracture transmissivities in Crystalline Rock using flow log measurements

  • Diffusion‐controlled tracer retention in Crystalline Rock on the field scale
    Geophysical Research Letters, 2010
    Co-Authors: Vladimir Cvetkovic
    Abstract:

    [1] Tracer retention is a key process for the barrier function of Crystalline Rock to any contaminant. Here we investigate the nature of retention mechanisms and their field-scale parametrization using results of a comprehensive tracer transport experiment in Crystalline Rock on the field scale (Aspo Hard Rock Laboratory, Sweden). A method for identifying dominant retention mechanisms and inferring key parameters on the site scale is presented. Taking advantage of multiple tracer tests with a wide range of sorption affinities, retention is shown to be diffusion-controlled. For the considered site, robust features of tracer migration can be reasonably well predicted within a Rock volume on at least 200 m scale, by combining independent information with a simple model.

  • transport and retention from single to multiple fractures in Crystalline Rock at aspo sweden 2 fracture network simulations and generic retention model
    Water Resources Research, 2010
    Co-Authors: Vladimir Cvetkovic, Andrew Frampton
    Abstract:

    Hydrogeologic characterization of Crystalline Rock formations on the field scale is important for many applications but still presents a multitude of challenges [Neuman, 2005]. In this work we use ...

Allen M Shapiro - One of the best experts on this subject based on the ideXlab platform.

  • effective matrix diffusion in kilometer scale transport in fractured Crystalline Rock
    Water Resources Research, 2001
    Co-Authors: Allen M Shapiro
    Abstract:

    Concentrations of tritium (3H) and dichlorodifluoromethane (CFC-12) in water samples taken from glacial drift and fractured Crystalline Rock over 4 km2 in central New Hampshire are interpreted to identify a conceptual model of matrix diffusion and the magnitude of the diffusion coefficient. Dispersion and mass transfer to and from fractures has affected the 3H concentration to the extent that the peak 3H concentration of the 1960s is no longer distinguishable. Because of heterogeneity in the bedRock the sparsely distributed chemical data do not warrant a three-dimensional transport model. Instead, a one-dimensional model of CFC-12 and 3H migration along flow lines in the glacial drift and bedRock is used to place bounds on the processes affecting kilometer-scale transport, arid model parameters are varied to reproduce the measured relation between 3H and CFC-12, rather than their spatial distributions. A model of mass exchange to and from fractures that is dependent on the time-varying concentration gradient at fracture surfaces qualitatively reproduces the measured relation between 3H and CFC-12 with an upper bound for the fracture dispersivity approximately equal to 250 m and a lower bound for the effective matrix diffusion coefficient equal to 1 m2 yr−1. The diffusion coefficient at the kilometer scale is at least 3 orders of magnitude greater than laboratory estimates of diffusion in Crystalline Rock. The large diffusion coefficient indicates that diffusion into an immobile fluid phase (Rock matrix) is masked at the kilometer scale by advective mass exchange between fractures with large contrasts in trarismissivity. The measured transmissivity of fractures in the study area varies over more than 6 orders of magnitude. Advective mass exchange from high-permeability fractures to low-permeability fractures results in short migration distances of a chemical constituent in low-permeability fractures over an extended period of time before reentering high-permeability fractures; viewed at the kilometer scale, this process is analogous to the chemical constituent diffusing into and out of an immobile fluid phase.

  • Effective matrix diffusion in kilometer‐scale transport in fractured Crystalline Rock
    Water Resources Research, 2001
    Co-Authors: Allen M Shapiro
    Abstract:

    Concentrations of tritium (3H) and dichlorodifluoromethane (CFC-12) in water samples taken from glacial drift and fractured Crystalline Rock over 4 km2 in central New Hampshire are interpreted to identify a conceptual model of matrix diffusion and the magnitude of the diffusion coefficient. Dispersion and mass transfer to and from fractures has affected the 3H concentration to the extent that the peak 3H concentration of the 1960s is no longer distinguishable. Because of heterogeneity in the bedRock the sparsely distributed chemical data do not warrant a three-dimensional transport model. Instead, a one-dimensional model of CFC-12 and 3H migration along flow lines in the glacial drift and bedRock is used to place bounds on the processes affecting kilometer-scale transport, arid model parameters are varied to reproduce the measured relation between 3H and CFC-12, rather than their spatial distributions. A model of mass exchange to and from fractures that is dependent on the time-varying concentration gradient at fracture surfaces qualitatively reproduces the measured relation between 3H and CFC-12 with an upper bound for the fracture dispersivity approximately equal to 250 m and a lower bound for the effective matrix diffusion coefficient equal to 1 m2 yr−1. The diffusion coefficient at the kilometer scale is at least 3 orders of magnitude greater than laboratory estimates of diffusion in Crystalline Rock. The large diffusion coefficient indicates that diffusion into an immobile fluid phase (Rock matrix) is masked at the kilometer scale by advective mass exchange between fractures with large contrasts in trarismissivity. The measured transmissivity of fractures in the study area varies over more than 6 orders of magnitude. Advective mass exchange from high-permeability fractures to low-permeability fractures results in short migration distances of a chemical constituent in low-permeability fractures over an extended period of time before reentering high-permeability fractures; viewed at the kilometer scale, this process is analogous to the chemical constituent diffusing into and out of an immobile fluid phase.

  • tracer transport in fractured Crystalline Rock evidence of nondiffusive breakthrough tailing
    Water Resources Research, 2000
    Co-Authors: Matthew W Becker, Allen M Shapiro
    Abstract:

    Extended tailing of tracer breakthrough is often observed in pulse injection tracer tests conducted in fractured geologic media. This behavior has been attributed to diffusive exchange of tracer between mobile fluids traveling through channels in fractures and relatively stagnant fluid between fluid channels, along fracture walls, or within the bulk matrix. We present a field example where tracer breakthrough tailing apparently results from nondiffusive transport. Tracer tests were conducted in a fractured Crystalline Rock using both a convergent and weak dipole injection and pumping scheme. Deuterated water, bromide, and pentafluorobenzoic acid were selected as tracers for their wide range in molecular diffusivity. The late time behavior of the normalized breakthrough curves were consistent for all tracers, even when the pumping rate was changed. The lack of separation between tracers of varying diffusivity indicates that strong breakthrough tailing in fractured geologic media may be caused by advective transport processes. This finding has implications for the interpretation of tracer tests designed to measure matrix diffusion in situ and the prediction of contaminant transport in fractured Rock.

Andrew Frampton - One of the best experts on this subject based on the ideXlab platform.

Christopher J Talbot - One of the best experts on this subject based on the ideXlab platform.

Jeanpierre Burg - One of the best experts on this subject based on the ideXlab platform.

  • permeability and seismic velocity anisotropy across a ductile brittle fault zone in Crystalline Rock
    Solid Earth, 2018
    Co-Authors: Quinn Wenning, Claudio Madonna, Antoine De Haller, Jeanpierre Burg
    Abstract:

    This study characterizes the elastic and fluid flow properties systematically across a ductile-brittle fault zone in Crystalline Rock at the Grimsel Test Site underground research laboratory. Anisotropic seismic velocities and permeability measured every 0.1 m in the 0.7 m across the transition zone from the host Grimsel granodiorite to the fault core show that foliation-parallel p - and s - wave velocities systematically increase from the host Rock towards the fault core, while permeability is reduced nearest to the fault core. The results suggest that although brittle deformation has persisted in the recent evolution, antecedent ductile fabric continues to control the matrix elastic and fluid flow properties outside the fault core. The juxtaposition of the ductile strain zone next to the brittle zone, which is bounded inside the two mylonitic fault cores, causes a significant elastic, mechanical, and fluid flow heterogeneity, which has important implications for crustal deformation and fluid flow, and exploitation and use of geothermal energy and geologic waste storage. The results illustrate how physical characteristics of faults in Crystalline Rocks change in fault zones during the ductile to brittle transitions.

  • Permeability and seismic velocity anisotropy across a ductile–brittle fault zone in Crystalline Rock
    Solid Earth, 2018
    Co-Authors: Quinn Wenning, Claudio Madonna, Antoine De Haller, Jeanpierre Burg
    Abstract:

    This study characterizes the elastic and fluid flow properties systematically across a ductile-brittle fault zone in Crystalline Rock at the Grimsel Test Site underground research laboratory. Anisotropic seismic velocities and permeability measured every 0.1 m in the 0.7 m across the transition zone from the host Grimsel granodiorite to the fault core show that foliation-parallel p - and s - wave velocities systematically increase from the host Rock towards the fault core, while permeability is reduced nearest to the fault core. The results suggest that although brittle deformation has persisted in the recent evolution, antecedent ductile fabric continues to control the matrix elastic and fluid flow properties outside the fault core. The juxtaposition of the ductile strain zone next to the brittle zone, which is bounded inside the two mylonitic fault cores, causes a significant elastic, mechanical, and fluid flow heterogeneity, which has important implications for crustal deformation and fluid flow, and exploitation and use of geothermal energy and geologic waste storage. The results illustrate how physical characteristics of faults in Crystalline Rocks change in fault zones during the ductile to brittle transitions.