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Tidwell, Vincent Carroll; Wilson, John L.

doi:10.1023/a:1007568632217

Cited by 47 publications

(6 citation statements)

References 28 publications

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“…This smoothing of the heterogeneity can be clearly verified as mentioned in previous research [16,73,74]. The block side sizes up to 1.0 m resulted in a small increase of the mean of up to 4%.…”

Section: Reproduction Of the Flow At The Coarse Scalesupporting

confidence: 87%

Stochastic analysis of three-dimensional hydraulic conductivity upscaling in a heterogeneous tropical soil

Godoy

Zuquette

Gómez‐Hernández

2018

Computers and Geotechnics

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Hydraulic conductivity (K) heterogeneity is seldom considered in geotechnical practice for the impossibility of sampling the entire area of interest and for the difficulty of accounting for scale effects. Stochastic three-dimensional K upscaling can tackle these two problems, and a workflow is described with an application in a tropical soil. The application shows that K heterogeneity can be incorporated in the daily practice of the geotechnical modeler while discussing the aspects to consider when performing the upscaling so that the upscaled models reproduce the average fluxes at the fine scale.

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Section: Reproduction Of the Flow At The Coarse Scalesupporting

confidence: 87%

Stochastic analysis of three-dimensional hydraulic conductivity upscaling in a heterogeneous tropical soil

Godoy

Zuquette

Gómez‐Hernández

2018

Computers and Geotechnics

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“…A reduction of up to 83.5 % of the variance with the increasing of the block side sizes was observed. This smoothing of the heterogeneity can be clearly verified as mentioned in previous research (Hunt, 2006;Tidwell & Wilson, 1999;Vik et al, 2013b).…”

Section: Resultssupporting

confidence: 86%

Upscaling of water flow and mass transport in a tropical soil: numerical, laboratory and field studies

Godoy¹

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Numerical models are becoming fundamental tools to predict a range of complex problems faced by geotechnical and geo-environmental engineers. However, to render the model reliable for future predictions, the model input parameters must be determined with consideration of the scale effects. If there is a difference of scales between the observation and the model scales there are two possible ways to consider it: or models are constructed with elements of a size similar to that at which the data were measured, or some upscaling rules must be defined. In this context, this thesis focuses on upscaling of water flow and mass transport in a tropical soil by means of numerical, laboratory and field studies. This thesis is organized in four parts.First, the heterogeneity, correlation and cross-correlation between solute transport parameters (dispersivity, α, and partition coefficient, Kd) and soil properties are studied in detail. In this part, it is verified that the hydraulic conductivity (K) and solute transport parameters are highly heterogeneous, while soil properties are not. Spatial correlation of α, K, and statistically significant variables are studied, and it would probably improve the estimation only in a small-scale study, since the spatial correlation are only observed up to 2.5 m. This study is a first attempt to evaluate the spatial variation in the correlation coefficient of transport parameters of a reactive and a nonreactive solute, indicating the more relevant variables and the one that should be included in future studies.In the second part, scale effect on K, dispersivity and partition coefficient of potassium and chloride are studied experimentally by means of laboratory and field experiments. The purpose is to contribute to the discussion about scale effects on K, α and Kd and understanding how these parameters behave with the change in the scale of measurement. Results show that K values increases with scale, regardless of the method of measurement, except for the results obtained from double-ring infiltrometer tests. Dispersivity trends to increase exponentially with the sample height.Partition coefficient tends to increase with sample length, diameter and volume. These differences in the parameters according to the scale of measurement must be considered when these observations are later used as input to numerical models, otherwise the responses can be misrepresented.x Third, stochastic analysis of three-dimensional hydraulic conductivity upscaling is performed using a simple average and the Laplacian-with-skin methods for a variety of block sizes based on real K measurements. In this part it is demonstrated the errors that can be introduced by using a deterministic upscaling using simple averages of the measured K without accounting for the spatial correlation. Results show that K heterogeneity can be incorporated in the daily practice of the geotechnical modeler.The aspects to consider when performing the upscaling are also discussed. Finally, the dependence of the exponent of the p-n...

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“…By using particle tracking calculations, they showed that sedimentary processes are responsible for the heterogeneities that determine local groundwater flow in aquifers. The importance of connectivity on fracture flow has also been acknowledged [e.g., Journel and Alabert, 1989;Tidwell and Wilson, 1999].…”

Section: Background and Literature Reviewmentioning

confidence: 99%

Spatial connectivity in a highly heterogeneous aquifer: From cores to preferential flow paths

Bianchi

Chen

Wilson

et al. 2011

Water Resources Research

120

106

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[1] This study investigates connectivity in a small portion of the extremely heterogeneous aquifer at the Macrodispersion Experiment (MADE) site in Columbus, Mississippi. A total of 19 fully penetrating soil cores were collected from a rectangular grid of 4 m by 4 m. Detailed grain size analysis was performed on 5 cm segments of each core, yielding 1740 hydraulic conductivity (K) estimates. Three different geostatistical simulation methods were used to generate 3-D conditional realizations of the K field for the sampled block. Particle tracking calculations showed that the fastest particles, as represented by the first 5% to arrive, converge along preferential flow paths and exit the model domain within preferred areas. These 5% fastest flow paths accounted for about 40% of the flow. The distribution of preferential flow paths and particle exit locations is clearly influenced by the occurrence of clusters formed by interconnected cells with K equal to or greater than the 0.9 decile of the data distribution (10% of the volume). The fraction of particle paths within the high-K clusters ranges from 43% to 69%. In variogram-based K fields, some of the fastest paths are through media with lower K values, suggesting that transport connectivity may not require fully connected zones of relatively homogenous K. The high degree of flow and transport connectivity was confirmed by the values of two groups of connectivity indicators. In particular, the ratio between effective and geometric mean K (on average, about 2) and the ratio between the average arrival time and the arrival time of the fastest particles (on average, about 9) are consistent with flow and advective transport behavior characterized by channeling along preferential flow paths.

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Untitled

Cited by 47 publications

References 28 publications

Stochastic analysis of three-dimensional hydraulic conductivity upscaling in a heterogeneous tropical soil

Stochastic analysis of three-dimensional hydraulic conductivity upscaling in a heterogeneous tropical soil

Upscaling of water flow and mass transport in a tropical soil: numerical, laboratory and field studies

Spatial connectivity in a highly heterogeneous aquifer: From cores to preferential flow paths

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