Solute transport in fractured rocks with stagnant water zone and rock matrix composed of different geological layers—Model development and simulations

Mahmoudzadeh, Batoul; Liu, Longcheng; Moreno, Luis; Neretnieks, Ivars

doi:10.1002/wrcr.20132

Cited by 42 publications

(28 citation statements)

References 24 publications

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“…Shahkarami et al (2015) and Mahmoudzadeh et al (2013). It suffices, however, for the need in the analysis of field tracer tests, and should be taken as the starting point before going deeper into complicated systems involving, e.g.…”

Section: Mathematical Model and Solution Proceduresmentioning

confidence: 99%

“…with the material property group for the rock matrix given by (Mahmoudzadeh et al 2013(Mahmoudzadeh et al , 2016)…”

Section: Mathematical Model and Solution Proceduresmentioning

confidence: 99%

“…where Gt w is actually MPG · FWS/Q, provided FWS is the area of flow-wetted-surface of the single fracture (Mahmoudzadeh et al 2013) over which solute is exchanged with the stagnant water in the rock matrix, and Q is the volumetric flow rate through the fracture.…”

Section: Solution To the Single-flow-path Modelmentioning

confidence: 99%

“…These models include the multi-rate mass transfer models (Haggerty and Gorelick 1995;Mahmoudzadeh et al 2013), the multi-continuum approaches (Šimůnek et al 2003;Šimůnek and van Genuchten 2008), the continuous time random walk approach (Berkowitz et al 2006), the time-domain random walk approach (Bodin 2015;Shahkarami et al 2016), the fractional advection-dispersion equation approach (Benson et al 2000), as well as the stochastic-convective transport approach (Cirpka and Kitanidis 2000;Ginn 2001).…”

Section: Introduction and Scopementioning

confidence: 99%

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Solute transport along a single fracture in a porous rock: a simple analytical solution and its extension for modeling velocity dispersion

et al. 2017

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A simple and robust solution is developed for the problem of solute transport along a single fracture in a porous rock. The solution is referred to as the solution to the singleflow-path model and takes the form of a convolution of two functions. The first function is the probability density function of residence-time distribution of a conservative solute in the fracture-only system as if the rock matrix is impermeable. The second function is the response of the fracture-matrix system to the input source when Fickian-type dispersion is completely neglected; thus, the effects of Fickian-type dispersion and matrix diffusion have been decoupled. It is also found that the solution can be understood in a way in line with the concept of velocity dispersion in fractured rocks. The solution is therefore extended into more general cases to also account for velocity variation between the channels. This leads to a development of the multi-channel model followed by detailed statistical descriptions of channel properties and sensitivity analysis of the model upon changes in the model key parameters. The simulation results obtained by the multi-channel model in this study fairly well agree with what is often observed in field experiments-i.e. the unchanged Peclet number with distance, which cannot be predicted by the classical advectiondispersion equation. In light of the findings from the aforementioned analysis, it is suggested that forced-gradient experiments can result in considerably different estimates of dispersivity compared to what can be found in naturalgradient systems for typical channel widths.

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Section: Mathematical Model and Solution Proceduresmentioning

confidence: 99%

“…with the material property group for the rock matrix given by (Mahmoudzadeh et al 2013(Mahmoudzadeh et al , 2016)…”

Section: Mathematical Model and Solution Proceduresmentioning

confidence: 99%

Section: Solution To the Single-flow-path Modelmentioning

confidence: 99%

Section: Introduction and Scopementioning

confidence: 99%

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Solute transport along a single fracture in a porous rock: a simple analytical solution and its extension for modeling velocity dispersion

et al. 2017

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“…It is expected that these regions contain the stressed crystals, whereas in the channels where water flows there are few, if any, stressed crystals. Until recently, Neretnieks [24] and Mahmoudzadeh et al [25] took the influence of the stagnant water zone in fracture plane into account. They found that solute diffusion into the stagnant water zone adjacent to the flow channel can significantly contribute to the retardation of solute.…”

Section: Introductionmentioning

confidence: 99%

Evolution of Fracture Aperture under Combined Effect of Stress and Flow

Mahmoudzadeh¹,

Liu²,

Moreno³

et al. 2016

IJCEA

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Fracture apertures may decrease or increase by different mechanical and chemical mechanisms when the fractures are subject to stress and flow. A model is presented to describe evolution of fracture aperture mediated by dissolution and precipitation. The model accounts for the fact that dissolved minerals carried by flowing water along the fracture can not only diffuse into and out of the adjacent rock matrix but also at first diffuse into the stagnant water zone existing in part of the fracture plane and then from there into and out of the rock matrix adjacent to it. This simple model allows us to gain some insights into which processes and mechanisms have the larger impact on the fracture aperture under different circumstances. The analytical solution in Laplace domain is used to study fracture closure/opening rate in a pseudo steady state procedure. It is found that the times involved for any changes in fracture aperture are very much larger than the times needed for concentrations of dissolved minerals to reach steady state in the rock matrix, the stagnant water zone and the flow channel. Moreover, it is shown that diffusion into the rock matrix, which acts as a strong sink or source for dissolved minerals, clearly dominates the rate of concentration change and consequently the rate of evolution of the fracture aperture.

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Hydrologic issues associated with nuclear waste repositories

2015

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Significant progress in hydrology, especially in subsurface flow and solute transport, has been made over the last 35 years because of sustained interest in underground nuclear waste repositories. The present paper provides an overview of the key hydrologic issues involved, and to highlight advances in their understanding and treatment because of these efforts. The focus is not on the development of radioactive waste repositories and their safety assessment, but instead on the advances in hydrologic science that have emerged from such studies. Work and results associated with three rock types, which are being considered to host the repositories, are reviewed, with a different emphasis for each rock type. The first rock type is fractured crystalline rock, for which the discussion will be mainly on flow and transport in saturated fractured rock. The second rock type is unsaturated tuff, for which the emphasis will be on flow from the shallow subsurface through the unsaturated zone to the repository. The third rock type is clay-rich formations, whose permeability is very low in an undisturbed state. In this case, the emphasis will be on hydrologic issues that arise from mechanical and thermal disturbances; i.e., on the relevant coupled thermo-hydromechanical processes. The extensive research results, especially those from multiyear large-scale underground research laboratory investigations, represent a rich body of information and data that can form the basis for further development in the related areas of hydrologic research. General IntroductionSignificant progress in hydrology, especially in subsurface flow and solute transport, has been made over the last 35 years because of sustained interest in the performance assessment of proposed underground nuclear waste repositories. The present paper attempts to provide an overview of the key hydrologic issues involved and to highlight the advances in their understanding and treatment because of these efforts. This paper is not focused on the development of high-level nuclear waste repositories and their safety assessment; it focuses instead on the advances in hydrologic science which have emerged from such studies. These advances may find applications in other hydrology-related problems of current importance at the national and international levels, such as environmental contamination remediation, carbon dioxide geosequestration, and natural gas production through fracking.In the next section, we present, in a general way, the context for the hydrologic framework related to performance and safety assessment of underground nuclear waste repositories that are proposed to be constructed in three particular rock formations-crystalline rock, unsaturated tuffs, and clays. Then, we discuss some particularly challenging factors concerning the research common to these three formations. This discussion will be followed by three sections devoted to each of these three rock types, respectively, to present a review of hydrologic research in these areas.

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Solute transport in fractured rocks with stagnant water zone and rock matrix composed of different geological layers—Model development and simulations

Cited by 42 publications

References 24 publications

Solute transport along a single fracture in a porous rock: a simple analytical solution and its extension for modeling velocity dispersion

Solute transport along a single fracture in a porous rock: a simple analytical solution and its extension for modeling velocity dispersion

Evolution of Fracture Aperture under Combined Effect of Stress and Flow

Hydrologic issues associated with nuclear waste repositories

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