scholarly journals Unified Packing Model for Improved Prediction of Porosity and Hydraulic Conductivity of Binary Mixed Soils

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 455
Author(s):  
Ammar El-Husseiny
Keyword(s):  
Hydraulic Conductivity ◽  
Current Model ◽  
Fine Sand ◽  
Coarse Sand ◽  
Published Data ◽  
Soil Mixing ◽  
Packing Model ◽  
Wide Range ◽  
The Impact ◽  
Mixed Soils

Binary mixed soils, containing coarse sand particles mixed with variable content of fines (fine sand, silt, or clay) are important for several environmental and engineering applications. The packing state (or porosity) of such sand-fines mixtures controls several important physical properties such as hydraulic conductivity. Therefore, developing an analytical packing model to predict porosity of binary mixed soils, based on properties of pure unmixed sand and fines (endmembers), can contribute to predicting hydraulic conductivity for the mixtures without the need for extensive laboratory measurements. Toward this goal, this study presents a unified packing model for the purpose of predicting the porosity and hydraulic conductivity of binary mixed soils as function of fines fraction. The current model modifies an existing packing model developed for coarse binary mixed soils to achieve three main improvements: (1) being inclusive of wide range of binary mixed soils covering the whole range particle sizes, (2) incorporating the impact of cohesive packing behavior of the fines on binary mixture porosity, and (3) accounting for the impact of clay swelling. The presented model is the first of its kind incorporating the combined impact of all three factors: particle size ratio, fines cohesive packing and swelling, on binary mixtures porosity. The predictions of the modified model are validated using experimental published data for the porosity of sand-fines mixtures from 24 different studies. The model shows significant improvement in predicting porosity compared to existing packing models that frequently underestimate the porosity. By using the predicted porosity as an input in Kozeny–Carman formulation, the absolute mean error in predicting hydraulic conductivity, as function of fines fraction for 16 different binary mixed soils, is reduced by 50% when compared to the use of the previous packing model. The current model provides insights about the endmembers properties (porosity, hydraulic conductivity, and grain size) and fines content required to achieve a certain target desirable porosity and hydraulic conductivity of the mixed soils. This can assist the optimization of soil mixing design for various applications.

scholarly journals Improved Packing Model for Functionally Graded Sand-Fines Mixtures—Incorporation of Fines Cohesive Packing Behavior

2020 ◽  
Vol 10 (2) ◽  
pp. 562
Author(s):  
Ammar El-Husseiny
Keyword(s):  
Fine Particles ◽  
Current Model ◽  
Functionally Graded ◽  
Analytical Models ◽  
Dry Density ◽  
Published Data ◽  
Fine Silt ◽  
Packing Model ◽  
Cohesive Particles ◽  
Mixed Soils

Binary soil mixture, containing large silica particles (sand) mixed with variable content of very fine silt or clay, is an example of a functionally graded material that is important for several science and engineering applications. Predicting the porosity (or void ratio), which is a fundamental quantity that affects other physical properties, of such material as function of fines (clay or silt) fraction can be significant for sediment research and material design optimization. Existing analytical models for porosity prediction work well for binary mixed soils containing multi-sized non-cohesive particles with no clay, while such models frequently underestimate the porosity of sand-clay mixtures. This study aims to present an analytical model that accurately predicts the porosity of mixed granular materials or soils containing sand and very fine silt or clay (cohesive particles). It is demonstrated that accounting for the cohesive nature of very fine particles, which exists due to the effect of inter-particle forces, is a major missing aspect in existing packing models for mixed soils. Consequently, a previously developed linear packing model is modified so that it accounts for fines cohesive packing in sand-fines mixtures. The model prediction is validated using various experimental published data sets for the porosity of sand-fines mixtures. Improvement in the prediction of permeability and maximum packing dry density when incorporating cohesive packing behavior is discussed. The current model also provides important insights on the conditions under which, the lowest permeability and maximum packing state are expected.

Sand type influences the energetics of nest escape in Brisbane river turtle hatchlings

2018 ◽  
Vol 66 (1) ◽  
pp. 27 ◽  
Author(s):  
Mohd Uzair Rusli ◽  
David T. Booth
Keyword(s):  
Fine Sand ◽  
Coarse Sand ◽  
Soil Types ◽  
Energetic Cost ◽  
Energy Reserves ◽  
Freshwater Turtles ◽  
Cohort Size ◽  
Substrate Type ◽  
Wide Range ◽  
Influence Of Substrate

Freshwater turtles can construct their nest in a wide range of soil types, and because different soil types have different physical characteristics such as particle size distribution and compactness, soil type presumably affects digging performance and the energetics of nest escape of turtle hatchlings. Previous studies have reported how cohort size affects the energetic cost of nest escape in turtle hatchlings, but no studies have reported the influence of substrate type on the energetic cost of nest escape. The time taken and the energy required by the same number of hatchlings to dig through two different sand types were quantified by open-flow respirometry. Brisbane river turtle hatchlings digging through fine sand escaped faster and spent less energy than hatchlings digging through coarse sand, and a larger cohort size provided a clear energetic advantage while digging in both sand types. Across all group sizes, hatchlings digging through fine sand spent 33.8% less energy compared with hatchlings digging through coarse sand. We conclude that hatchlings emerging from nests constructed in fine sand have an energetic advantage over hatchlings emerging from nests constructed in course sand because they would have greater energy reserves upon reaching the nest’s surface.

scholarly journals Modeling 3-D permeability distribution in alluvial fans using facies architecture and geophysical acquisitions

2017 ◽  
Vol 21 (2) ◽  
pp. 721-733 ◽  
Author(s):  
Lin Zhu ◽  
Huili Gong ◽  
Zhenxue Dai ◽  
Gaoxuan Guo ◽  
Pietro Teatini
Keyword(s):  
Spatial Distribution ◽  
Hydraulic Conductivity ◽  
Flow Direction ◽  
Three Dimensional ◽  
Fine Sand ◽  
Coarse Sand ◽  
Alluvial Fan ◽  
Alluvial Fans ◽  
Statistical Parameters ◽  
Depositional Processes

Abstract. Alluvial fans are highly heterogeneous in hydraulic properties due to complex depositional processes, which make it difficult to characterize the spatial distribution of the hydraulic conductivity (K). An original methodology is developed to identify the spatial statistical parameters (mean, variance, correlation range) of the hydraulic conductivity in a three-dimensional (3-D) setting by using geological and geophysical data. More specifically, a large number of inexpensive vertical electric soundings are integrated with a facies model developed from borehole lithologic data to simulate the log10(K) continuous distributions in multiple-zone heterogeneous alluvial megafans. The Chaobai River alluvial fan in the Beijing Plain, China, is used as an example to test the proposed approach. Due to the non-stationary property of the K distribution in the alluvial fan, a multiple-zone parameterization approach is applied to analyze the conductivity statistical properties of different hydrofacies in the various zones. The composite variance in each zone is computed to describe the evolution of the conductivity along the flow direction. Consistently with the scales of the sedimentary transport energy, the results show that conductivity variances of fine sand, medium-coarse sand, and gravel decrease from the upper (zone 1) to the lower (zone 3) portion along the flow direction. In zone 1, sediments were moved by higher-energy flooding, which induces poor sorting and larger conductivity variances. The composite variance confirms this feature with statistically different facies from zone 1 to zone 3. The results of this study provide insights to improve our understanding on conductivity heterogeneity and a method for characterizing the spatial distribution of K in alluvial fans.

scholarly journals Experimental study on filter media using locally available materials in bioretention

2019 ◽  
Vol 68 (8) ◽  
pp. 757-768 ◽  
Author(s):  
Feikai Yang ◽  
Rajendra Prasad Singh ◽  
Dangfang Fu
Keyword(s):  
Hydraulic Conductivity ◽  
Filter Material ◽  
Fine Sand ◽  
Yangtze River Delta ◽  
Coarse Sand ◽  
Easy Access ◽  
Filter Media ◽  
Local Climate ◽  
Yangtze River Delta Region ◽  
Selection Of

Abstract Bioretention systems and selection of effective filter media are very important in implementation of sponge cities. The current study was carried out to find proper composition of filter media using locally available materials, which acclimate to the special/local climate, environmental and geographical conditions in Yangtze River Delta region. Results revealed that sand with discontinuous gradation and containing a certain amount of clay led to unsatisfactory hydraulic performance (hydraulic conductivity ranged from 423 mm/h to 1,054 mm/h, and 1,500 mm/h to 29 mm/h). In contrast, a mixture of locally available sand, which consisted of continuous gradation of coarse sand (40–70%, by mass), fine sand (0–40%, by mass), very fine sand (10–60%, by mass) and nutrient soil (0–3%, by mass), had a hydraulic conductivity ranging from 200 to 400 mm/h and relatively stable structure. During the 70 days' flooding test, the hydraulic conductivity changed in the first 20 days due to the migration of particles (mainly <0.6 mm) and then became stable; the stable value was close to the initial. Moreover, easy access and simple production processes made it easier to promote. Findings could be used as a guideline for implementation of bioretention systems and selection of locally available and effective filter material.

Effects of different dispersion and fine fraction determination methods on the results of routine particle size analysis

Soil Research ◽  
1987 ◽  
Vol 25 (4) ◽  
pp. 347 ◽  
Author(s):  
PJ Thorburn ◽  
RJ Shaw
Keyword(s):  
Particle Size ◽  
Fine Fraction ◽  
Fine Sand ◽  
Particle Size Analysis ◽  
Coarse Sand ◽  
Size Analysis ◽  
Wide Range ◽  
Effective Dispersion ◽  
Determination Methods ◽  
Fraction Determination

Particle-size analysis (PSA) methods to be used in routine situations need to be rapid, require no prior information about the sample and give precise results over a wide range of soil textures. Effects of three physical dispersion and two fine-fraction determination methods on PSA results were investigated over a wide range of soil textures to find the most appropriate technique for routine PSA. Interactions between physical dispersion and fine-fraction determination methods were also investigated. The reciprocating shaker produced significantly lower silt and fine sand and higher coarse sand (and clay, although not significant) values than either drink mixer or end-over-end shaker dispersions. This result was interpreted as the reciprocating shaker giving the most effective dispersion, with aggregated clay being dispersed to primary particles while coarse sand was not fragmented to fine sand or silt. The end-over-end shaker did not reliably disperse a heavy clay soil, and so cannot be recommended for routine use where similar soils may be encountered. When considered over all soils and dispersion methods, hydrometer clay and clay + silt values were higher than pipette values. These results were due to the effective depth of the hydrometer being greater, on average, than the depth of the pipette. However, there were interactions between dispersion and fine-fraction determination methods for the clay and clay +silt classes. Hydrometer values were greater than pipette values with drink mixer and end-over-end shaker dispersion, but were similar with reciprocating shaker dispersion. For the clay fraction, inferior dispersion given by the drink mixer and end-over-end shaker resulted in a significant mass of particles between the sampling depths of the pipette and hydrometer, causing the higher hydrometer values. For the clay +silt fraction, both drink mixer and end-over-end dispersion methods fragmented sands to a size which was recorded by the hydrometer but not the pipette. These interactions highlighted the requirement for effective dispersion where clay and silt are determined by the hydrometer, and may explain some of the conflicting observations of the precision of the hydrometer compared with the pipette. Reciprocating shaker physical dispersion combined with the hydrometer fine-fraction determination method was found the most appropriate PSA method combination for use in a routine situation.

Saturated Hydraulic Conductivity of Scandinavian Tills

1990 ◽  
Vol 21 (2) ◽  
pp. 107-118 ◽  
Author(s):  
Bo B. Lind ◽  
Lars Lundin
Keyword(s):  
Grain Size ◽  
Hydraulic Conductivity ◽  
Hydraulic Properties ◽  
Flow Direction ◽  
Published Data ◽  
Soil Horizons ◽  
Wide Range ◽  
Mean Grain Size ◽  
Distinctive Difference ◽  
The Relationship

There is a distinctive difference in hydraulic properties between the upper horizons of Scandinavian till soil and the deeper C-horizon. The hydraulic conductivity has been studied in different soil profile types, mainly Podzolic variants. In the topsoil there are correlations from grain size and porosity to hydraulic conductivity. Both porosity and hydraulic conductivity are stratified with depth. Often high conductivity appears in the upper soil horizons decreasing with depth to low values at about one metre. This pattern varies with soil type. The soils vary with topographic location as does the groundwater level. Published data on hydraulic conductivity in the C-horizon of sandy-silty tills in Scandinavia covers a wide range, from about 5 × 10−9 m/s to 5 × 10−4 m/s, with a mean of 3 × 10−6 m/s. The correlation between porosity and hydraulic conductivity, as well as between mean grain size and hydraulic conductivity, is weak in the C-horizon. It is concluded that the sediment structure has a decisive influence on the hydraulic conductivity of till. A model of the relationship between fabric (in relation to water flow direction), the porosity in the poresize interval 30-95 μm and the hydraulic conductivity is presented.

scholarly journals The Impact of Hemodynamic Reflex Compensation Following Myocardial Infarction on Subsequent Ventricular Remodeling

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Colleen M. Witzenburg ◽  
Jeffrey W. Holmes
Keyword(s):  
Myocardial Infarction ◽  
Ventricular Remodeling ◽  
Experimental Studies ◽  
Left Ventricular ◽  
Published Data ◽  
Compensatory Mechanisms ◽  
Compensatory Response ◽  
Wide Range ◽  
Reflex Compensation ◽  
The Impact

Patients who survive a myocardial infarction (MI) are at high risk for ventricular dilation and heart failure. While infarct size is an important determinant of post-MI remodeling, different patients with the same size infarct often display different levels of left ventricular (LV) dilation. The acute physiologic response to MI involves reflex compensation, whereby increases in heart rate (HR), arterial resistance, venoconstriction, and contractility of the surviving myocardium act to maintain mean arterial pressure (MAP). We hypothesized that variability in reflex compensation might underlie some of the reported variability in post-MI remodeling, a hypothesis that is difficult to test using experimental data alone because some reflex responses are difficult or impossible to measure directly. We, therefore, employed a computational model to estimate the balance of compensatory mechanisms from experimentally reported hemodynamic data. We found a strikingly wide range of compensatory reflex profiles in response to MI in dogs and verified that pharmacologic blockade of sympathetic and parasympathetic reflexes nearly abolished this variability. Then, using a previously published model of postinfarction remodeling, we showed that observed variability in compensation translated to variability in predicted LV dilation consistent with published data. Treatment with a vasodilator shifted the compensatory response away from arterial and venous vasoconstriction and toward increased HR and myocardial contractility. Importantly, this shift reduced predicted dilation, a prediction that matched prior experimental studies. Thus, postinfarction reflex compensation could represent both a source of individual variability in the extent of LV remodeling and a target for therapies aimed at reducing that remodeling.

scholarly journals Modelling 3D permeability distribution in alluvial fans using facies architecture and geophysical acquisitions

2016 ◽  
Author(s):  
Lin Zhu ◽  
Huili Gong ◽  
Zhenxue Dai ◽  
Gaoxuan Guo ◽  
Pietro Teatini
Keyword(s):  
Spatial Distribution ◽  
Hydraulic Conductivity ◽  
Flow Direction ◽  
Three Dimensional ◽  
Fine Sand ◽  
Coarse Sand ◽  
Alluvial Fan ◽  
Alluvial Fans ◽  
Statistical Parameters ◽  
Depositional Processes

Abstract. Alluvial fans are highly heterogeneous due to complex depositional processes, which make difficult to characterize the spatial distribution of the hydraulic conductivity K. An original methodology is developed to identify the spatial statistical parameters (mean, variance, correlation range) of the hydraulic conductivity in a three-dimensional setting by using geological and geophysical data. The Chaobai River alluvial fan in the Beijing Plain, China, is used as an example to test the proposed approach. Due to the non-stationary property of the K distribution in the alluvial fan, a multi-zone parameterization approach is applied to analyze the conductivity statistical properties of different hydrofacies in the various zones. The composite variance in each zone is computed to describe the evolution of the conductivity along the flow direction. Consistently with the scales of the sedimentary transport energy, the results show that conductivity variances of fine sand, medium-coarse sand, and gravel decrease from the upper (Zone 1) to the lower (Zone 3) portion along the flow direction. In Zone 1, sediments were moved by higher-energy flooding, which induces bad sorting and larger conductivity variances. The composite variance confirms this feature with statistically different facies from Zone 1 to Zone 3. The results of this study provide insights to improve our understanding on conductivity heterogeneity and a method for characterizing the spatial distribution of K in alluvial fans.

scholarly journals Fabrication of Permeameter for Determination of Hydraulic Conductivity of Earth Materials

2020 ◽  
Vol 9 (4) ◽  
pp. 1204-1210
Keyword(s):  
Hydraulic Conductivity ◽  
Engineering Design ◽  
Low Cost ◽  
Pressure Head ◽  
Fine Sand ◽  
Coarse Sand ◽  
Silty Clay ◽  
Earth Dams ◽  
Soil Hydraulic Conductivity

Laboratory investigation is one of the major ways of assessing soil hydraulic conductivity. Determination of hydraulic conductivity aids in engineering design of well pumping, prediction concerning spread of polluting fluids, embankment of canal bank affected by seepage, flooding solutions and stability of earth dams. However, different studies have shown that there are alternative models to Darcy’s law which governs the widely use of laboratory measurement of hydraulic conductivity. The deficiencies accustomed to the conventional permeameter such as the time wastage and cost-intensivehas led to different research modification. A low-cost permeameter was fabricated using a plastic column, hose pipe, to serve as water inlet and outlet connected to two manometer tubes to measure the pressure head difference. The hydraulic conductivities measured using the lowcost were 4.31 cm/s, 8.14 cm/s, 6.12 cm/s, 5.86 cm/s for 0.3 mm coarse sand, 0.85-1 mm fine sand, sandy clay and silty clay respectively. In comparison of the fabricated permeameter with conventional permeameter and other fabricated laboratory permeameters, it was observed that the hydraulic conductivity obtained is consistent with the typical permeability range for each soil type.

scholarly journals Sediment type and breeding strategy of the Bank Swallow Riparia riparia in western Sweden

Ornis Svecica ◽  
2002 ◽  
Vol 12 (3) ◽  
pp. 157-163
Author(s):  
Bo-Bertil Lind ◽  
Jimmy Stigh ◽  
Lars Larsson
Keyword(s):  
Hydraulic Conductivity ◽  
Bulk Density ◽  
Fine Sand ◽  
Coarse Sand ◽  
Breeding Strategy ◽  
Sediment Type ◽  
Medium Sand ◽  
Riparia Riparia ◽  
Bank Swallow ◽  
Sand Pits

This paper presents an investigation of the sediment used by the Bank Swallow (Sand Martin) Riparia riparia for the construction of breeding tunnels. Grain-size distribution, bulk density and hydraulic conductivity of breeding-tunnel sediment were investigated at four localities in western Sweden. The investigation shows that the Bank Swallow was consistent in using layers composed of a narrow range of fine and medium sand. Ninety percent of the investigated breeding burrows were located in fine to medium sand (0.125–0.5 mm) and 10% in coarse sand (0.5–1.0 mm). No breeding tunnels were found in sediment finer than fine sand or coarser than coarse sand. The fine to medium sand fraction has the properties to hold stable walls and keep dry tunnels even during rainy periods with heavy infiltration. The hydraulic conductivity of the sediment was in the range of 10–4 to 10–3 m/s and the bulk density 1,510–1,575 kg/m3. In Sweden, artificially excavated slopes in gravel and sand pits have long been the dominating breeding locality for the Bank Swallow. However, during the last two decades, four major factors have led to the decrease of breeding localities: (1) a decreasing demand of aggregate resources, (2) landscaping of gravel and sand pits and stabilization of eroding slopes, including river banks and shorelines, (3) a change to quarries as a source for aggregate production, and (4) concentrating gravel and sand exploitation to fewer and larger pits. It is concluded that these factors are important for the decline of the Bank Swallow population in Sweden and possibly elsewhere in Europe and North America.

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