Laboratory and simulation studies of solute transport in fracture networks

Hull, L.C.; Miller, Jonathan D.; Clemo, Tom

doi:10.1029/wr023i008p01505

Cited by 47 publications

(24 citation statements)

References 12 publications

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“…But the concentration of a particle still cannot affect the transfer probability of the particle. Therefore both of these two extreme case models are too simplified to describe the solute transfer characteristics of the junction in most cases [Hull et al, 1987;Berkowitz et al, 1994].…”

Section: Discussionmentioning

confidence: 99%

Analytical solutions for solute transfer characteristics at continuous fracture junctions

Park¹,

Lee²

1999

Water Resources Research

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Abstract. Simple analytical solutions for the mixing characteristics and transfer probabilities of solute at the continuous fracture junction are proposed in this study. The proposed analytical solution considers the effects of diffusion, and it is simple enough to be applied to the junctions in discrete fracture network. The analytical solutions are compared with the complete-mixing and the streamline-routing models. As the Peclet number increases, the analytical solutions indicate the transition from complete solute mixing to streamline routing at a fracture junction. It is clear from the results that the transfer characteristics at the junctions are a function not only of one dimensionless parameter but of complex combinations of discharge pattern, geometry, and concentration distribution in the related fractures. Comparisons with the existing numerical solutions and possible underestimation of the solute mixing by the analytical solutions are discussed. IntroductionDiscrete and continuum approaches arc two main branches in mod½ling the fluid flow and solute transport in fractured rocks. The conventional continuum mod½l is simple, but it has its limits because of the inability to correctly account for the effect of natural discontinuity geometry and to determine the irregular range and degree of contamination. Thus the simulation using the discrete fracture system or the hybrid discrete continuum system has become increasingly popular they suggested a random walk model at the junction to account for the mixing accelerated by diffusion. In this model the mixing of solute by diffusion across the streamline is explained by the normal probability distribution, and they concluded that the mixing characteristics affect the dispersion to a much further degree than was previously considered. Berkowitz et al.[1994] developed a transport model by using Philip's [1988] analytic solution for fluid flow and particle tracking and a random walk method to evaluate quantitatively the mixing characteristics at discontinuity junction in terms of the Peclet number (Pe), that is, the ratio of the diffusion to the convection. By using this model, they intended to determine the transport conditions under which the complete-mixing and the streamline-routing theories can be applied. Recently, Stockman et al.[1997] suggested a new modeling method to appropriately incorporate the boundary effects by using cellular automata to recognize the importance of the boundary conditions in low-Peclet number transport conditions. As a result, these numerical studies concluded that complete-mixing and streamline-routing theories are valid only in the limited ranges of the Peclet number. Though these experimental and theoretical studies have been performed to date, mixing at the discontinuity junction due to the diffusion is very difficult to incorporate in the analysis of solute transport through the discrete fracture network. The solute transfer characteristics at fracture junctions might be computed numerically, but it requires too much numeri...

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Section: Discussionmentioning

confidence: 99%

Analytical solutions for solute transfer characteristics at continuous fracture junctions

Park¹,

Lee²

1999

Water Resources Research

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“…This is commonly known as the dual-porosity model (Figure 1). The solute residence time in the fracture was assumed to be large enough that molecular diffusion homogenized the concentration profile across the fracture aperture [Hull et al, 1987]. This was verified by comparing the calculated diffusion distances (2D•') •/2 (where D is the free water diffusion coefficient and…”

Section: Conceptual Modelmentioning

confidence: 99%

Using multiple experimental methods to determine fracture/matrix interactions and dispersion of nonreactive solutes in saturated volcanic tuff

Callahan¹,

Reimus²,

Bowman³

et al. 2000

Water Resources Research

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Abstract. The objective of this research was to investigate the effects of matrix diffusion on solute transport in fractured volcanic tuff. Two tuff cores were studied, one with a matrix porosity of 0.27 and the other with a porosity of 0.14. The matrix permeabilities of the cores were 4.7 x 10 -•5 and 7.8 x 10 -•9 m 2, 5 and 9 orders of magnitude less than the respective fracture permeabilities. This suggested that the cores could be modeled as dualporosity systems with no flow in the matrix but significant solute storage capacity. Two types of tracer tests were conducted in each fractured core: (1) iodide was injected in separate experiments at different flow rates and (2) two tracers of different matrix diffusion coefficients (bromide and pentafluorobenzoate (PFBA)) were injected in another test. A difference in the maximum concentrations of the solutes and the extended tailing of the breakthrough curves were assumed to be indicative of diffusive mass transfer between the fracture and the porous matrix of the cores. Interpreting the results from both methods allowed the identification of matrix diffusion and dispersion effects within the fracture by simultaneously fitting the data sets (with known constraints) using a relatively simple conceptual model. Estimates of mass transfer coefficients for the fractured cores were also obtained. IntroductionBecause solute transport is controlled by both the physical nature of the flow system and the characteristics of the solutes (velocity, dispersivity, water saturation, sorption behavior, and diffusion coefficient), it is often difficult to determine the im- Separate samples of each core were used for matrix diffusion coefficient, porosity, and permeability measurements. These experiments provided independent estimates of the matrix diffusion coefficients of the different solutes used in the fractured core experiments.The dual-porosity conceptual model accurately described solute transport through the fractured cores and captured the importance of fracture/matrix interactions. The solute breakthrough curves follow a -1.5 slope in log space, which is probably due to diffusive mass transfer between the fracture and the surrounding porous matrix. However, the independent matrix diffusion coefficient measurements for Br-and PFBA in the same rock types were smaller than those calculated from 3547

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“…al., 1992), (Middleton and Quigley, 1990), (Hull et. al., 1987), (Gillham et al, 1984), (Sudicky and Frind, 1982), (Tang et al, 1981), .…”

Section: Contaminant Transport Through Fractured Mediamentioning

confidence: 99%

“…Diffusion of mass into the porous matrix adjacent to the fracture has been studied by Hull et al, (1987), Gillham et al, (1984), and . This research noted that transport occurred by two mechanisms, advection fluid flow through the fracture and diffusion into the adjacent porous media.…”

Section: Diffusion In Fractured Mediamentioning

confidence: 99%

“…Concentration profile in a fracture of aperture, 2b, with a constant source input, Co and zero concentration boundaries at the center of the matrix blocks at high flow velocities (after ) 29 Figure 9. Fracture residence time necessary for homogenization of tracer across the fracture width by molecular diffusion (after Hull et al, 1987) 31 Figure 10. Relative permeability as a function of saturation (after Palmer and Johnson, 1989) 34 Figure 11.…”

Section: List Of Tablesmentioning

confidence: 99%

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Transport and fate of a LNAPL in fractured clayey till

Mackiewicz

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Laboratory and simulation studies of solute transport in fracture networks

Cited by 47 publications

References 12 publications

Analytical solutions for solute transfer characteristics at continuous fracture junctions

Analytical solutions for solute transfer characteristics at continuous fracture junctions

Using multiple experimental methods to determine fracture/matrix interactions and dispersion of nonreactive solutes in saturated volcanic tuff

Transport and fate of a LNAPL in fractured clayey till

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