Journal ArticleDOI
Numerical modeling of two species radionuclide transport in a single fracturematrix system with variable fracture aperture
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In this article, a fully implicit finite difference model has been developed, which incorporates fracture aperture width variation in the numerical study of two species radionuclide transport, and two distinct geometric profiles namely, sinusoidal and logarithmic have been used to capture the variation of aperture width.Abstract:
A variable aperture model, instead of a conventional parallel plate model, is utilized to study the transport of radionuclides in a single coupled fracture-matrix system. A fully implicit finite difference model has been developed, which incorporates fracture aperture width variation in the numerical study of two species radionuclide transport. Two distinct geometric profiles namely, sinusoidal and logarithmic have been used to capture the variation of aperture width. The dependence of advection, hydrodynamic dispersion, linear sorption, and matrix diffusion on aperture width is considered in the analysis of radionuclides transport. Two species (parent and daughter) radioactive decay chain is also incorporated. There is a greater retardation of radionuclides in fracture for the variable aperture model than the parallel plate model. Sensitivity analysis on fracture surface sorption coefficient, longitudinal dispersivity, matrix porosity, and matrix diffusion coefficient shows that the conventional parallel plate model overestimate the radionuclide concentration in the fracture when compared to the variable aperture model.read more
Citations
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VALIDITY OF CUBIC LAW FOR FLUID FLOW IN A DEFORMABLE ROCK FRACTURE - eScholarship
Abstract: The validity of the cubic law for laminar flow of fluids through open fractures consisting of parallel planar plates has been established by others over a wide range of conditions with apertures ranging down to a minimum of 0.2 µm. The law may be given in simplified form by Q/Δh = C(2b)3, where Q is the flow rate, Δh is the difference in hydraulic head, C is a constant that depends on the flow geometry and fluid properties, and 2b is the fracture aperture. The validity of this law for flow in a closed fracture where the surfaces are in contact and the aperture is being decreased under stress has been investigated at room temperature by using homogeneous samples of granite, basalt, and marble. Tension fractures were artificially induced, and the laboratory setup used radial as well as straight flow geometries. Apertures ranged from 250 down to 4µm, which was the minimum size that could be attained under a normal stress of 20 MPa. The cubic law was found to be valid whether the fracture surfaces were held open or were being closed under stress, and the results are not dependent on rock type. Permeability was uniquely defined by fracture aperture and was independent of the stress history used in these investigations. The effects of deviations from the ideal parallel plate concept only cause an apparent reduction in flow and may be incorporated into the cubic law by replacing C by C/ƒ. The factor ƒ varied from 1.04 to 1.65 in these investigations. The model of a fracture that is being closed under normal stress is visualized as being controlled by the strength of the asperities that are in contact. These contact areas are able to withstand significant stresses while maintaining space for fluids to continue to flow as the fracture aperture decreases. The controlling factor is the magnitude of the aperture, and since flow depends on (2b)3, a slight change in aperture evidently can easily dominate any other change in the geometry of the flow field. Thus one does not see any noticeable shift in the correlations of our experimental results in passing from a condition where the fracture surfaces were held open to one where the surfaces were being closed under stress.
Journal ArticleDOI
Study on three-dimensional fracture network connectivity path of rock mass and seepage characteristics based on equivalent pipe network
TL;DR: In this article, an approach using MATLAB cell array instead of traditional adjacency matrix to search and store fracture network connectivity paths was presented. But the results of this approach are limited.
Journal ArticleDOI
Modeling of radionuclide transport in porous media: A review of recent studies
Igor Medved,Robert Černý +1 more
TL;DR: An overview of recent studies in which the transport of radionuclides in porous materials has been recently modeled is provided in this paper, where the focus is on the modeling based on balance equations whose results could be used in nuclear waste management for the prediction of long-term behavior and assessment of safety standards.
Journal ArticleDOI
Numerical calculation and multi-factor analysis of slurry diffusion in an inclined geological fracture
TL;DR: In this article, the authors investigated the restriction mechanisms, based on a single inclined rough fracture, employing a space stepwise method (SSM) using multi-direction sectors (MDS) for calculating the diffusion of variable-viscosity slurry under constant flow.
Journal ArticleDOI
Effects of Cemented Porous Media on Temporal Mixing Behavior of Conservative Solute Transport
TL;DR: In this article, the influence of the cemented porous media and Peclet number (Pe) on the temporal mixing behavior was investigated, and it was found that the spatial velocity variability of the flow field was enhanced as cementation degree increased.
References
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Journal ArticleDOI
Validity of Cubic Law for fluid flow in a deformable rock fracture
TL;DR: The validity of the cubic law for laminar flow of fluids through open fractures consisting of parallel planar plates has been established by others over a wide range of conditions with apertures ranging down to a minimum of 0.2 µm.
VALIDITY OF CUBIC LAW FOR FLUID FLOW IN A DEFORMABLE ROCK FRACTURE - eScholarship
Abstract: The validity of the cubic law for laminar flow of fluids through open fractures consisting of parallel planar plates has been established by others over a wide range of conditions with apertures ranging down to a minimum of 0.2 µm. The law may be given in simplified form by Q/Δh = C(2b)3, where Q is the flow rate, Δh is the difference in hydraulic head, C is a constant that depends on the flow geometry and fluid properties, and 2b is the fracture aperture. The validity of this law for flow in a closed fracture where the surfaces are in contact and the aperture is being decreased under stress has been investigated at room temperature by using homogeneous samples of granite, basalt, and marble. Tension fractures were artificially induced, and the laboratory setup used radial as well as straight flow geometries. Apertures ranged from 250 down to 4µm, which was the minimum size that could be attained under a normal stress of 20 MPa. The cubic law was found to be valid whether the fracture surfaces were held open or were being closed under stress, and the results are not dependent on rock type. Permeability was uniquely defined by fracture aperture and was independent of the stress history used in these investigations. The effects of deviations from the ideal parallel plate concept only cause an apparent reduction in flow and may be incorporated into the cubic law by replacing C by C/ƒ. The factor ƒ varied from 1.04 to 1.65 in these investigations. The model of a fracture that is being closed under normal stress is visualized as being controlled by the strength of the asperities that are in contact. These contact areas are able to withstand significant stresses while maintaining space for fluids to continue to flow as the fracture aperture decreases. The controlling factor is the magnitude of the aperture, and since flow depends on (2b)3, a slight change in aperture evidently can easily dominate any other change in the geometry of the flow field. Thus one does not see any noticeable shift in the correlations of our experimental results in passing from a condition where the fracture surfaces were held open to one where the surfaces were being closed under stress.
Journal ArticleDOI
Hydraulic conductivity of rock fractures
TL;DR: In this article, the authors derived the cubic law of the Navier-Stokes equations for flow between smooth, parallel plates and showed that the effective hydraulic aperture is less than the mean aperture, by a factor that depends on the ratio of the mean value of the aperture to its standard deviation.
Journal ArticleDOI
Diffusion in the rock matrix: An important factor in radionuclide retardation?
TL;DR: In this paper, the authors analyzed the accessibility of the rock matrix to radio-nuclides and showed that the diffusion of the nuclides into the rock matrices and their sorption onto the surfaces of the microfissures are the main mechanisms retarding migration from a repository.
Journal ArticleDOI
Contaminant Transport in Fractured Porous Media: Analytical Solution for a Single Fracture
TL;DR: In this paper, a general analytical solution is developed for the problem of contaminant transport along a discrete fracture in a porous rock matrix, which takes into account advective transport in the fracture, longitudinal mechanical dispersion in a fracture, molecular diffusion along the fracture axis, adsorption into the face of the matrix, adhesion within the matrix and radioactive decay.
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