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  • Soils and Foundations
  • 1
    Language: English
    In: Soils and Foundations, August 2016, Vol.56(4), pp.676-690
    Description: Mass transport in soils occurs through pore networks that are highly affected by basic physical properties such as the degree of compaction, and particle size and shape. In this study, micro-focus X-ray computed tomography (CT) was used to obtain information on the pore network structure at different compaction levels for repacked columns of sands and glass beads representing different size fractions and particle shapes. Mass transport parameters, including gas diffusion coefficient ( ) and air permeability ( ) at variably saturated conditions, were measured on the same columns using standard methods, and literature data on saturated hydraulic conductivity ( ) for the same materials were analyzed. A comparison of X-ray CT derived pore network structure and physical parameters showed that the round sands and glass beads exhibited larger pores, a higher pore coordination number, and a lower volumetric surface area than that of angular sands at the same particle size, resulting in higher as well as higher and under relatively dry conditions. The X-ray CT derived the mean pore diameter ( ), and the pore coordination number ( ) for each material correlated well with key gas transport properties such as percolation thresholds and pore network connectivity. A predictive model from wet to dry conditions based fully on X-ray CT derived parameters ( and ) was developed and showed good agreement with measured for both round and angular sands.
    Keywords: Micro-Focus X-Ray CT ; Pore Structure ; Mass Transport Parameters ; Engineering
    ISSN: 0038-0806
    Source: ScienceDirect Journals (Elsevier)
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  • 2
  • 3
    Language: English
    In: SOILS AND FOUNDATIONS, 2011, Vol.51(1), pp.123-132
    Description: Colloid-facilitated transport enhances migration of strongly sorbing compounds (e.g., radionuclides, phosphorus, heavy metals) in soil and groundwater. Mobilization, transport and deposition of soil colloids are the underlying processes governing colloid-facilitated contaminant transport. Although significant progress has been made in simulating mobilization and transport/deposition of model colloids in different collector systems, it may be inadequate for the prediction of natural colloidal behavior in the subsurface. This study quantifies the leaching of natural volcanic ash soil colloids (NC) as well as the simultaneous transport of applied water dispersible soil colloids (WDC) in aggregated volcanic ash soil columns. Two water-saturated soil columns were irrigated with artificial irrigation water (AIW) at an intensity of 80 mm/hr for 60 hours. Two additional columns were irrigated at the same intensity, but a colloidal suspension of 5 mg/L was applied after 20 hours for a period of 20 hours. Effluent colloid concentrations were measured in each experiment. HYDRUS-1D was used for the simulation and estimation of colloid transport parameters. The results clearly showed different kinetics for applied colloid transport and natural colloid leaching. Transport of applied WDC followed first-order attachment kinetics, while the two-site equilibrium/kinetic model with equal fractions of equilibrium and kinetic sites best described the leaching of NC. Coupling these best model approaches well predicted the simultaneous leaching of natural and applied colloids, hereby providing a useful tool for the design of colloid-based in-situ soil remediation systems.〈br〉
    Keywords: Chemical Non-Equlibrium ; Column Experiment ; Leaching ; Soil Colloids ; Two-Site Equilibrium/Kinetic Model ; Volcanic Ash Soil ; Water Dispersible Colloids ; (≪B≫Igc≪/B≫: D4/E7)
    ISSN: 0038-0806
    E-ISSN: 18811418
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  • 4
    Language: English
    In: Soils and Foundations, 04/2014, Vol.54(2), pp.116-125
    Description: The subsurface of the Earth is facing evermore thermal impact due to global warming, urban heat islands, and the widespread use of ground source heat pump (GSHP) systems. This potentially causes changes in its physical, mechanical, microbiological, and chemical properties, and in the subsurface water quality. To predict and evaluate this thermal impact (or thermal pollution), a better understanding and improved models for the thermal properties governing heat transport in subsurface sediments are needed. Also, data acquisition in high spatial resolution for the thermal properties and basic physical properties of the subsurface sediments are essential. In this study, the main thermal properties (the thermal conductivity, heat capacity, and thermal diffusivity) together with the basic physical properties (the soil texture, water content, and dry bulk density) were measured on boring core samples representing depths from 0 to 50 or 80 m, at three study sites in the Kanto area of Japan. Based on the measured data, models for thermal conductivity as functions of gravimetric water content, dry bulk density, and volumetric sand content were developed. The new models performed markedly better than presently available models from the literature and, in combination with a modified de Vries type model for heat capacity, the resulting model for thermal diffusivity was capable of describing the measured data well. The usefulness of the newly developed models were validated and illustrated by using data from a two-day thermal response test (TRT) performed at one of the three study sites. The new predictive models for the thermal properties used in a numerical heat transport simulation accurately predicted subsurface (5–50 m) temperature changes during the TRT.
    Keywords: Engineering;
    ISSN: 00380806
    Source: Elsevier (via CrossRef)
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  • 5
    Language: English
    In: SOILS AND FOUNDATIONS, 2008, Vol.48(3), pp.397-406
    Description: Risk assessment and design of remediation methods at soil sites polluted with gaseous phase contaminant require an accurate description of soil-gas diffusion coefficient (〈i〉D〈/i〉〈sub〉p〈/sub〉) which is typically governed by the variations in soil air-filled porosity (〈i〉v〈/i〉〈sub〉a〈/sub〉). For undisturbed volcanic ash soils, recent studies have shown that a linear 〈i〉D〈/i〉〈sub〉p〈/sub〉(〈i〉v〈/i〉〈sub〉a〈/sub〉) model, taking into account inactive air-filled pore space (threshold soil-air content, 〈i〉v〈/i〉〈sub〉a, th〈/sub〉), captured the 〈i〉D〈/i〉〈sub〉p〈/sub〉 data across the total soil moisture range from wet to completely dry conditions. In this study, we developed a simple, easy to apply, and still accurate linear 〈i〉D〈/i〉〈sub〉p〈/sub〉(〈i〉v〈/i〉〈sub〉a〈/sub〉) model for undisturbed volcanic ash soils. The model slope 〈i〉C〈/i〉 and intercept (interpreted as 〈i〉v〈/i〉〈sub〉a, th〈/sub〉) were derived using the classical Buckingham (1904) 〈i〉D〈/i〉〈sub〉p〈/sub〉(〈i〉v〈/i〉〈sub〉a〈/sub〉) power-law model, 〈i〉v〈/i〉〈sub〉a〈/sub〉〈sup〉〈i〉X〈/i〉〈/sup〉, at two soil-water matric potentials of pF 2 (near field capacity condition) and pF 4.1 (near wilting point condition), and assuming the same value for the Buckingham exponent (〈i〉X〈/i〉=2.3) in agreement with measured data. This linear 〈i〉D〈/i〉〈sub〉p〈/sub〉(〈i〉v〈/i〉〈sub〉a〈/sub〉) prediction model performed better than the traditionally-used non-linear 〈i〉D〈/i〉〈sub〉p〈/sub〉(〈i〉v〈/i〉〈sub〉a〈/sub〉) models, especially at dry soil conditions, when tested against several independent data sets from literature. Model parameter sensitivity analysis on soil compaction effects showed that a decrease in slope 〈i〉C〈/i〉 and 〈i〉v〈/i〉〈sub〉a, th〈/sub〉 due to uniaxial reduction of air-filled pore space in between aggregates markedly affects the magnitude of soil-gas diffusivity. We recommend the new 〈i〉D〈/i〉〈sub〉p〈/sub〉(〈i〉v〈/i〉〈sub〉a〈/sub〉) model using only the soil-air contents at two soil-water matric potential conditions (field capacity and wilting point) for a rapid assessment of the entire 〈i〉D〈/i〉〈sub〉p〈/sub〉-〈i〉v〈/i〉〈sub〉a〈/sub〉 function.〈br〉
    Keywords: Air-Filled Porosity ; Soil-Gas Diffusion Coefficient ; Soil-Gas Diffusivity ; Soil-Water Retention ; Volcanic Ash Soil ; (≪B≫Igc≪/B≫: D4/E14)
    ISSN: 0038-0806
    E-ISSN: 18811418
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  • 6
    Language: English
    In: 地盤工学会論文報告集 / 地盤工学会論文報告集編集委員会 編, 2003-06, Vol.43(3), pp.105~114
    Description: Title Transcription: Soil Constituent Facilitated Transport of Phosphorus from a High P Surface Soil
    Description: Material Type: 記事・論文
    Keywords: Colloidal Matter ; Colloidal Phosphorus ; Dissolved Organic Matter ; Dom ; Dissolved Phosphorus ; Dom-Facilitated Transport ; Phosphorus Sorption Coefficient (Kpsc)
    ISSN: 13417452
    ISSN: 00380806
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