A comparison of estimated and calculated effective porosity

Stephens, Daniel B.; Hsu, Kuo Chin; Prieksat, M. A.; Ankeny, Mark D.; Blandford, Neil; Roth, Tracy L.; Kelsey, James A.; Whitworth, Julia

doi:10.1007/s100400050141

Cited by 93 publications

(63 citation statements)

References 15 publications

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“…The effective porosity values from the expanded equation (0.6-5.0%) were more similar to those previously calculated from field-scale tracer-based studies conducted in unconsolidated, heterogeneous, and fine-grained granular porous media, whereas those from the truncated equation (0.1-1.3%) were more similar to those from fractured porous media (Gelhar et al 1992;Hall et al 1991;Stephens et al 1998). Based on the hydrogeology of the study site, i.e., silty and clayey fill, the effective porosity values from the expanded equation are likely more accurate than those from the truncated equation.…”

supporting

confidence: 79%

“…Field-scale tracer-based studies have shown that effective porosity in granular porous media can range from 40% (alluvial sediments; fine sands, and glacial till) to 0.4% (layered medium sand) and in fractured porous media from 60% (fractured dolomite and limestone) to 0.5% (fractured chalk) (Gelhar et al 1992). There is also increasing evidence that effective porosity is dependent on the scale at which it is assessed, which suggests that field-scale methods may be more appropriate to inform groundwater models (Li 1995;Stephens et al 1998). …”

Section: Introductionmentioning

confidence: 99%

“…Estimation-based methods have the disadvantage of being indirect but are relatively simple to conduct. Methods to calculate effective porosity typically rely on conducting tracer-based tests and interpretation of subsequent breakthrough curves (Stephens et al 1998). Tracer-based methods have the advantage of being direct but can be relatively difficult to conduct, especially at the field scale.…”

Section: Introductionmentioning

confidence: 99%

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Push-pull tests for estimating effective porosity: expanded analytical solution and in situ application

et al. 2017

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The analytical solution describing the onedimensional displacement of the center of mass of a tracer during an injection, drift, and extraction test (push-pull test) was expanded to account for displacement during the injection phase. The solution was expanded to improve the in situ estimation of effective porosity. The truncated equation assumed displacement during the injection phase was negligible, which may theoretically lead to an underestimation of the true value of effective porosity. To experimentally compare the expanded and truncated equations, single-well push-pull tests were conducted across six test wells located in a shallow, unconfined aquifer comprised of unconsolidated and heterogeneous silty and clayey fill materials. The push-pull tests were conducted by injection of bromide tracer, followed by a nonpumping period, and subsequent extraction of groundwater. The values of effective porosity from the expanded equation (0.6-5.0%) were substantially greater than from the truncated equation (0.1-1.3%). The expanded and truncated equations were compared to data from previous push-pull studies in the literature and demonstrated that displacement during the injection phase may or may not be negligible, depending on the aquifer properties and the push-pull test parameters. The results presented here also demonstrated the spatial variability of effective porosity within a relatively small study site can be substantial, and the error-propagated uncertainty of effective porosity can be mitigated to a reasonable level (< ± 0.5%).The tests presented here are also the first that the authors are aware of that estimate, in situ, the effective porosity of finegrained fill material.

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supporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Push-pull tests for estimating effective porosity: expanded analytical solution and in situ application

et al. 2017

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“…The second simulation (green line in Hydraulic properties were based on auger hole descriptions and verified using REGIS II, the database for Dutch hydrogeological information. Total porosity at the site was measured at 49 %, effective porosity was estimated at 25 %, in line with findings of Stephens et al (1998). The anisotropy factor, horizontal conductivity over vertical conductivity (k h /k v ), was set to 5 for the entire model (Vernes and Van Doorn 2005).…”

Section: D Column Basic Modelmentioning

confidence: 85%

Cation exchange in a temporally fluctuating thin freshwater lens on top of saline groundwater

2016

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In coastal-zone fields with a high groundwater level and sufficient rainfall, freshwater lenses are formed on top of saline or brackish groundwater. The fresh and the saline water meet at shallow depth, where a transition zone is found. This study investigates the mixing zone that is characterized by this salinity change, as well as by cation exchange processes, and which is forced by seepage and by rainfall which varies as a function of time. The processes are first investigated for a onedimensional (1D) stream tube perpendicular to the interface concerning salt and major cation composition changes. The complex sequence of changes is explained with basic cation exchange theory. It is also possible to show that the sequence of changes is maintained when a two-dimensional field is considered where the upward saline seepage flows to drains. This illustrates that for cation exchange, the horizontal component (dominant for flow of water) has a small impact on the chemical changes in the vertical direction. The flow's horizontal orientation, parallel to the interface, leads to changes in concentration that are insignificant compared with those that are found perpendicular to the interface, and are accounted for in the 1D flow tube. Near the drains, differences with the 1D considerations are visible, especially in the longer term, exceeding 100 years. The simulations are compared with field data from the Netherlands which reveal similar patterns.

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“…Trabalhos que tratam deste assunto determinam a permeabilidade a partir de um parâmetro denominado de porosidade efetiva, que é a relação entre vazios interconectados (por onde passa o fluxo) e o volume total do material e que pode ser determinada com traçadores por ensaios de campo ou de laboratório (HALL; LUFTRELL; CRONIN, 2001;STEPHENS et al, 1998;VERMA, 2011). Dessa forma, os autores sugerem para trabalhos futuros o estudo da porosidade efetiva do solo do CEEG e da relação desta com a permeabilidade saturada de solo.…”

Section: Quadro 3-resultados Dos Ensaios De Laboratóriounclassified

Permeabilidade de Solo Laterítico por Diferentes Métodos

et al. 2015

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Permeabilidade é uma propriedade de extrema importância para dimensionamento de diferentes tipos de obras de engenharia e é quantificada através do coeficiente de permeabilidade. Apesar do grande uso, ainda existem questionamentos sobre a melhor forma de determinação do coeficiente de permeabilidade. As principais questões são: (1) o tipo de método a ser utilizado e (2) a representatividade de amostras em solos tropicais. Neste contexto, objetivou-se neste trabalho a avaliação da permeabilidade de um solo laterítico, através da comparação de valores de coeficiente de permeabilidade determinados por ensaios in situ e em laboratório. Para tanto, escolheu-se o solo laterítico do Campo Experimental de Engenharia Geotécnica (CEEG) da Universidade Estadual de Londrina (UEL) e quatro equipamentos: permeâmetro de Carga Constante, permeâmetro de Carga Variável, permeâmetro de Guelph e Infiltrômetro. Os resultados mostram que, com exceção do permeâmetro de Carga Constante, todos os métodos apresentaram valor médio de coeficiente de permeabilidade da ordem de 10 -3 cm/s para coeficientes de variação de 37% a 92%. A heterogeneidade da estrutura do solo laterítico (em macro e microporos) é o provável condicionante da variabilidade encontrada. ResumoSoil Permeability is an important property of soil used to dimension several types of engineering works, and it can be quantified by the permeability rates. Despite of the great use, the type of the re doubts about the best way to determine de permeability rates. The main questions are: (1) the type of the method and (2) the reproducibility of samples in tropical soils. So, the objective of this work is to evaluate the permeability of a lateritic soil by comparing values of permeability coefficient determined for laboratory and in situ testing. For this, it was chosen the lateritic soil of Campo Experimental de Engenharia Geotécncia (CEEG) of the Universidade Estadual de Londrina (UEL) and four equipments: constant and variable head permeameters, Guelph permeameter and infiltrometer. The results show that all the methods present mean value of permeability coefficient on the order of 10 -3 cm/s whit variation coefficient in range of 37% to 92% , except the constant permeameter. The heterogeneous structure of lateritic soil (in macro and micro pores) is the probably determinant of the variability observed.

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A comparison of estimated and calculated effective porosity

Cited by 93 publications

References 15 publications

Push-pull tests for estimating effective porosity: expanded analytical solution and in situ application

Push-pull tests for estimating effective porosity: expanded analytical solution and in situ application

Cation exchange in a temporally fluctuating thin freshwater lens on top of saline groundwater

Permeabilidade de Solo Laterítico por Diferentes Métodos

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