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.

Development and verification of a coefficient of permeability function for a deformable unsaturated soil

1998 ◽  
Vol 35 (3) ◽  
pp. 411-425 ◽  
Author(s):  
Shangyan Huang ◽  
S L Barbour ◽  
D G Fredlund
Keyword(s):  
Porous Medium ◽  
Unsaturated Soil ◽  
Void Ratio ◽  
Constant Volume ◽  
Saturated Soil ◽  
Silty Sand ◽  
Degree Of Saturation ◽  
Experimental Program ◽  
Coefficient Of Permeability ◽  
Permeability Function

The modelling of flow through saturated/unsaturated soils has become routine in geotechnical and geo-environmental engineering. The analysis requires that the coefficient of permeability for an unsaturated soil be defined. The coefficient of permeability can be estimated based on currently available procedures. However, each procedure has limitations and consequently cares should be taken in the selection of a proper procedure. The coefficient of permeability of a saturated soil is a function of void ratio. The coefficient of permeability of an unsaturated soil of constant volume, is a function of the degree of saturation. However, soil is deformable and both the degree of saturation and the void-ratio influence the coefficient of permeability of a compressible, unsaturated soil. In this paper, the literature pertaining to the coefficient of permeability function for an unsaturated soil of constant volume and the coefficient of permeability for a deformable saturated soil are reviewed. A new coefficient of permeability function for a deformable unsaturated porous medium is then developed. A series of triaxial permeameter tests on unsaturated silty sand are described and the results from the experimental program are analyzed using the general form of the newly developed permeability function. The results show good agreement between the experimental data and the proposed model for a deformable unsaturated porous medium.Key words: unsaturated soil, coefficient of permeability, permeability function, soil-water characteristic curve, triaxial permeameter, deformable porous medium.

Predicting the permeability function for unsaturated soils using the soil-water characteristic curve

1994 ◽  
Vol 31 (4) ◽  
pp. 533-546 ◽  
Author(s):  
D.G. Fredlund ◽  
Anqing Xing ◽  
Shangyan Huang
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Characteristic Curve ◽  
Degree Of Saturation ◽  
Residual Water ◽  
Soil Water Characteristic Curve ◽  
Coefficient Of Permeability ◽  
Permeability Function

The coefficient of permeability for an unsaturated soil is primarily determined by the pore-size distribution of the soil and can be predicted from the soil-water characteristic curve. A general equation, which describes the soil-water characteristic curve over the entire suction range (i.e., from 0 to 106 kPa), was proposed by the first two authors in another paper. This equation is used to predict the coefficient of permeability for unsaturated soils. By using this equation, an evaluation of the residual water content is no longer required in the prediction of the coefficient of permeability. The proposed permeability function is an integration form of the suction versus water content relationship. The proposed equation has been best fit with example data from the literature where both the soil-water characteristic curve and the coefficient of permeability were measured. The fit between the data and the theory was excellent. It was found that the integration can be done from zero water content to the saturated water content. Therefore, it is possible to use the normalized water content (volumetric or gravimetric) or the degree of saturation data versus suction in the prediction of the permeability function. Key words : coefficient of permeability, soil-water characteristic curve, unsaturated soil, water content, 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.

Soil-water characteristic curve and permeability function for unsaturated cracked soil

2011 ◽  
Vol 48 (7) ◽  
pp. 1010-1031 ◽  
Author(s):  
J.H. Li ◽  
L.M. Zhang ◽  
X. Li
Keyword(s):  
Soil Water ◽  
Characteristic Curve ◽  
Crack Development ◽  
Volume Changes ◽  
Soil Matrix ◽  
Soil Water Characteristic Curve ◽  
Permeability Function ◽  
Pore Size Distributions ◽  
Crack Volume ◽  
Cracked Soil

Cracks are widely present in natural and engineered soils. As water infiltration into a cracked soil often starts from unsaturated conditions, the soil-water characteristic curve (SWCC) and permeability function for the cracked soil are required when conducting seepage analysis. This paper presents a method to predict the SWCC and permeability function for cracked soil considering crack volume changes during drying–wetting processes. The cracked soil is viewed as an overlapping continuum of a crack network system and a soil matrix system. The pore-size distributions for the two pore systems at a particular state can be determined and used to estimate the SWCCs and permeability functions. The estimated SWCCs and permeability functions for the two pore systems can be combined to give the SWCC and the permeability function for the cracked soil at that state. Then, the SWCC and permeability function for the cracked soil at different states along a crack development path can be obtained and combined to give the SWCC or permeability function for the cracked soil considering crack volume changes. Examples are presented to illustrate the prediction of the SWCCs and permeability functions for a cracked soil along five crack development paths.

Research on the Retention Capacity of Ruins Soil under Drying Condition

2014 ◽  
Vol 580-583 ◽  
pp. 705-710
Author(s):  
Ping Liu ◽  
Hu Yuan Zhang ◽  
Yi Chen ◽  
Xian Xian Shao ◽  
Xin Yuan Fu
Keyword(s):  
Water Content ◽  
Void Ratio ◽  
Characteristic Curve ◽  
Matric Suction ◽  
Soil Samples ◽  
Degree Of Saturation ◽  
Drying Process ◽  
Retention Capacity ◽  
Pore Water Pressures ◽  
The Relationship

The soil water characteristic curve (SWCC) has been tested during the drying process. In order to define the relationship between suction, degree of saturation and void ratio, fitting models of SWCC was established. Studies have shown that the shape of SWCC of three kinds of samples (taken from Jiaohe, Gaochang and Jiuzhoutai) was similar to the inverted “S”, the relationship between water content and matric suction was inversely proportional. Under the condition of the same moisture, the matric suction of the Jiaohe and Gaochang samples were greater than the Jiuzhoutai samples, and the changes of pore water pressures showed the same trend. The degree of saturation began to decrease when the water content reduced to the air entry value. When the degree of saturation was greater than 90%, the volume of soil samples contracted significantly, and when saturation is below 80%, volume shrinkage stopped.

Freezing Shrinkage in Compacted Clays

1966 ◽  
Vol 3 (1) ◽  
pp. 1-17 ◽  
Author(s):  
A B Hamilton
Keyword(s):  
Volume Change ◽  
Field Data ◽  
Degree Of Saturation ◽  
Volume Changes ◽  
Cement Pastes ◽  
Unidirectional Freezing ◽  
Observed Behaviour ◽  
Lacustrine Clay ◽  
Compactive Effort ◽  
Compacted Clays

This paper presents the results of volume change measurements on laboratory-compacted samples of five Alberta clay soils which have been subjected to closed-system, unidirectional freezing. It was found that for Standard AASHO compaction effort, maximum shrinkage occurred at degrees of saturation between 60 and 70 per cent. The compacted degree of saturation required for 0 per cent total volume change ranged from 86 to 90 per cent. Maximum freezing shrinkage was found to increase with an increase in plasticity of the soil. Increasing the compactive effort from Standard to Modified AASHO caused a reduction in the maximum measured shrinkage in a highly plastic, lacustrine clay. A hypothesis, based on Powers' and Helmuth's theory of volume changes in cement pastes on freezing, is suggested as a simplified explanation of the observed behaviour. Field data are presented showing the effects of subgrade freezing on the changes in surface elevation of an asphalt-surfaced highway.

scholarly journals An estimation of the soil water characteristics curves of Trinidad's expansive clays

2020 ◽  
Vol 195 ◽  
pp. 03009
Author(s):  
Damian V A Alexander ◽  
Kyung Ho Park ◽  
Derek Anthony Gay
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Volume Change ◽  
Characteristic Curve ◽  
Degree Of Saturation ◽  
Expansive Clay ◽  
Contributing Factors ◽  
Wet Season ◽  
Potential Measurement ◽  
Expansive Clays

Volume change behaviour of expansive clays has been one of the leading causes of damage to civil infrastructures worldwide. Contributing factors that lead to failures relate to changes in water content within the soil. Variations of water content can vary significantly based on an area’s climate regime. Trinidad has two seasons, the dry season (January to June) and the wet season (July to December). This variation leads to volume changes of expansive clay, where they exist mainly within the central and south regions of Trinidad. These areas are densely populated by residential and commercial buildings, which can be susceptible to damages from unsaturated expansive clays. The Soil Water Characteristic Curve (SWCC) for expansive clays is critical to estimate their unsaturated properties for the analysis of water flow movement. This study investigates the SWCCs for two expansive clay soil types in Trinidad. A WP4-T (Water Potential Measurement) is used to measure soil suction. The shrinkage curve (SC) test is conducted to consider the volume change of soil. The Fredlund and Xing (1994) SWCC equation and Fredlund and Zhang (2013) SC equation are used to fit the measured data. The SWCCs in terms of gravimetric and volumetric water contents and degree of saturation are compared. It is found that the normalised degree of saturation SWCC can provide a better display of the SWCC and estimation of the air-entry value.

scholarly journals A methodology for the formulation of water retention models in deformable soils

2021 ◽  
Author(s):  
Domenico Gallipoli ◽  
Agostino Walter Bruno
Keyword(s):  
Water Retention ◽  
Void Ratio ◽  
Laboratory Data ◽  
Degree Of Saturation ◽  
Integration Constant ◽  
Soil Water Retention ◽  
Retention Models ◽  
Two Parameters ◽  
Differential Coupling ◽  
Water Ratio

AbstractThis paper presents a novel approach to soil–water retention modelling that is based on the analysis of the material pore network. The approach postulates the existence of a differential coupling function, which relates the variation of water ratio to the variation of void ratio at constant suction. Distinct differential coupling functions have been considered, and the most general option has been integrated in a closed-form relationship between water ratio and void ratio with a suction-dependent integration constant, whose expression describes the isochoric retention behaviour. Four alternative expressions of the suction-dependent integration constant have been proposed resulting in four different, but equivalent, models linking degree of saturation, void ratio and suction. Each model predicts the variation of degree of saturation by means of four parameters, namely two parameters accounting for the effect of void ratio and two parameters accounting for the effect of suction. The models have been calibrated against laboratory data from soils with distinct particle size distributions and have shown accurate predictions of degree of saturation at different levels of suction and void ratio. Validation against additional data has also indicated that the models can extrapolate the soil behaviour to stress paths and suction levels beyond those considered during calibration.

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