Hydraulic properties for soils that undergo volume change as soil suction is increased

2015 ◽  
pp. 383-392
Author(s):  
F Zhang ◽  
D Fredlund ◽  
G Wilson
Keyword(s):  
Volume Change ◽  
Hydraulic Properties ◽  
Soil Suction

Equations for the entire soil-water characteristic curve of a volume change soil

2008 ◽  
Vol 45 (4) ◽  
pp. 443-453 ◽  
Author(s):  
Hung Q. Pham ◽  
Delwyn G. Fredlund
Keyword(s):  
Soil Water ◽  
Volume Change ◽  
Curve Fitting ◽  
Characteristic Curve ◽  
Engineering Practice ◽  
Soil Suction ◽  
Residual Soil ◽  
Soil Water Characteristic Curve ◽  
Geoenvironmental Engineering ◽  
Type Studies

Numerous curve-fitting equations have been proposed for soil-water characteristic curves. While these equations have been of considerable value in geotechnical and geoenvironmental engineering, the equations are not able to adequately fit gravimetric soil-water characteristic curve data over the entire range of soil suction for a soil that changes volume when suction is changed. Two new equations for the soil-water characteristic curve are presented in this paper. One equation has curve-fitting parameters that bear a meaningful relationship to conventional physical soil properties (e.g., air-entry value and residual soil suction), but the equation is somewhat complex. The equation is particularly useful for sensitivity type studies when undertaking computer modeling. The other equation is relatively simple to use and is developed as a conventional curve-fitting equation. The two equations are used to best-fit several soil datasets. Both equations perform well and can be used in research and engineering practice to define the gravimetric water content versus soil suction relationship for a soil exhibiting volume change.

scholarly journals Soil cracking propagation due to dryness and its relation to suction

2021 ◽  
Vol 337 ◽  
pp. 01021
Author(s):  
Elisangela do Prado Oliveira ◽  
Karoline Soecki ◽  
Vitor Pereira Faro ◽  
Alessander Christopher Morales Kormann
Keyword(s):  
Intensity Factor ◽  
Water Content ◽  
Soil Water ◽  
Hydraulic Properties ◽  
Clay Content ◽  
Water Infiltration ◽  
Soil Suction ◽  
Weather Variables ◽  
Hydraulic Behaviour ◽  
Soil Cracks

Investigation of Crack Intensity Factor is essential as it affects the mechanical and hydraulic behaviour of soils. Soil water coming from the wet seasons or from the water table, is removed by evaporation during the driest season. The loss of water provokes a significant increase in suction. When it exceeds the tensile strength of the soil, cracks occur that can modify the mechanical and mainly hydraulic properties of the soil, creating preferred paths for water infiltration. Little research is conducted on quantifying cracking in soil relating it to its hydraulic properties. This research aims to investigate the cracking of soils with focus on analysing its relation to water content and soil suction. Soils from a specific region in Brazil with clay predominance are collected and characterized. Unsaturated soil specimens are prepared and subjected to environmental real conditions in order to progressively check the consequences caused by the environment in soils with different clay content during four weeks. The Crack Intensity Factor is measured along the time through image processing. The water content is monitored through volume water content sensors. The measured results are evaluated to correlate crack intensity factor as function of weather variables and soil water content.

scholarly journals Using inverse analysis to estimate hydraulic properties for unsaturated layered sand

2020 ◽  
Vol 4 (2) ◽  
pp. First
Author(s):  
Tô Viết Nam ◽  
Nguyễn Việt Kỳ
Keyword(s):  
Inverse Analysis ◽  
Hydraulic Properties ◽  
Numerical Study ◽  
Characteristic Curve ◽  
Soil Column ◽  
Fine Sand ◽  
Soil Suction ◽  
Medium Sand ◽  
Sand Column ◽  
Inverse Simulation

In order to better evaluate the applicability of the inverse analysis method for calculation and evaluation of hydraulic properties of unsaturated soil in more realistic conditions, a transient one – step outflow experiment for layered sands was applied in the desaturation process with the purpose to attain the profiles of suction, saturation and flow rate with time. In this study, the fine sand and medium sand were used with the same thickness of 40cm for each layer. The sand grains were mixed under water and scooped into the plexiglas column (H = 80cm, D = 28cm, wall thickness = 1cm) to prepare a fully saturated sample. For homogeneity within each sand layer, the density of two sands must be controlled during soil column construction. For numerical study, the inverse simulation and one straightforward calculation were carried out to determine the unsaturated hydraulic properties of sands. Unsaturated hydraulic parameters in the van Genuchten model were estimated using soil suction measurements at 10cm intervals and an outflow rate at the bottom of a layered sand column. To reduce the quantity of data for analysis and simulation but still keep enough typical information for the experiment, four data sets of soil suction and saturation at four locations (L2, L4, L5 and L8) were selected out of eight to compile the Soil Water Characteristic Curve. The comparison between predicted unsaturated hydraulic properties and the experimental unsaturated hydraulic properties shows good agreement in the case of the fine sand was overlaid with medium sand. The results concluded that besides the homogeneous sand, the inverse analysis based on the 1-D outflow experiment promises to be a useful method in determining the hydraulic properties for unsaturated heterogeneous sand.

scholarly journals Permeability function for oil sands tailings undergoing volume change during drying

2018 ◽  
Vol 55 (2) ◽  
pp. 191-207 ◽  
Author(s):  
Feixia Zhang ◽  
G. Ward Wilson ◽  
D.G. Fredlund
Keyword(s):  
Volume Change ◽  
Oil Sands ◽  
Void Ratio ◽  
Characteristic Curve ◽  
Laboratory Data ◽  
Degree Of Saturation ◽  
Soil Suction ◽  
Volume Changes ◽  
Permeability Function ◽  
Oil Sands Tailings

The coefficient of permeability function is an important unsaturated soil property required when modeling seepage and contaminant transport phenomena. Inaccuracies in the estimation of the permeability function can lead to significant errors in numerical modeling results. Changes in void ratio and degree of saturation are factors that influence the permeability function. Presently available methodologies for estimating the unsaturated permeability function make the assumption that there is no volume change as soil suction is changed. As a result, volume changes are interpreted as changes in degree of saturation. The commonly used estimation techniques for the permeability function are reasonable for soils such as sands that experience little volume change as soil suction is changed. On the other hand, inaccurate results are generated when soils undergo volume change as is the case with oil sands tailings. Revisions to previous methodologies are proposed to render the estimation of the permeability function more suitable for simulating the drying process associated with soils that undergo high volume changes. The revised methodology independently analyzes the effect of volume changes (i.e., changes in void ratio) and degree of saturation changes (i.e., changes in S-SWCC (degree of saturation - soil-water characteristic curve)). Laboratory data on thickened oil sands tailings are presented and interpreted within the context of the proposed methodology.

Artifacts caused by dehydration and epoxy embedding in TEM

1991 ◽  
Vol 49 ◽  
pp. 338-339
Author(s):  
Hilton H. Mollenhauer
Keyword(s):  
Electron Microscopy ◽  
Electron Beam ◽  
Volume Change ◽  
Tissue Damage ◽  
Beam Specimen ◽  
Chemical Fixation ◽  
Resin Impregnation ◽  
Storage Vesicles ◽  
A Cell ◽  
Tissue Shrinkage

Various means have been devised to preserve biological specimens for electron microscopy, the most common being chemical fixation followed by dehydration and resin impregnation. It is intuitive, and has been amply demonstrated, that these manipulations lead to aberrations of many tissue elements. This report deals with three parts of this problem: specimen dehydration, epoxy embedding resins, and electron beam-specimen interactions. However, because of limited space, only a few points can be summarized.Dehydration: Tissue damage, or at least some molecular transitions within the tissue, must occur during passage of a cell or tissue to a nonaqueous state. Most obvious, perhaps, is a loss of lipid, both that which is in the form of storage vesicles and that associated with tissue elements, particularly membranes. Loss of water during dehydration may also lead to tissue shrinkage of 5-70% (volume change) depending on the tissue and dehydrating agent.

Short-term volume and turgor regulation in yeast

2008 ◽  
Vol 45 ◽  
pp. 147-160 ◽  
Author(s):  
Jörg Schaber ◽  
Edda Klipp
Keyword(s):  
Dynamic Model ◽  
Volume Change ◽  
Volume Regulation ◽  
Time Course ◽  
Osmotic Shock ◽  
Intracellular Concentration ◽  
Short Term ◽  
Hydrodynamic Property ◽  
Turgor Regulation ◽  
Thermodynamic Framework

Volume is a highly regulated property of cells, because it critically affects intracellular concentration. In the present chapter, we focus on the short-term volume regulation in yeast as a consequence of a shift in extracellular osmotic conditions. We review a basic thermodynamic framework to model volume and solute flows. In addition, we try to select a model for turgor, which is an important hydrodynamic property, especially in walled cells. Finally, we demonstrate the validity of the presented approach by fitting the dynamic model to a time course of volume change upon osmotic shock in yeast.

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