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.

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.

Using time domain reflectometry in triaxial testing

2000 ◽  
Vol 37 (6) ◽  
pp. 1325-1331
Author(s):  
J LH Grozic ◽  
M E Lefebvre ◽  
P K Robertson ◽  
N R Morgenstern
Keyword(s):  
Cyclic Loading ◽  
Water Content ◽  
Time Domain ◽  
Void Ratio ◽  
Time Domain Reflectometry ◽  
Volumetric Water Content ◽  
Degree Of Saturation ◽  
Triaxial Testing ◽  
Empirical Correlations ◽  
Static And Cyclic Loading

Time domain reflectometry (TDR) can be used to determine the volumetric water content of soils. This note describes the utilization of a TDR miniprobe in triaxial testing. The TDR performance was examined with a series of tests that not only proved its reliability but also resulted in two empirical correlations. Using these correlations, the degree of saturation and volumetric water content during triaxial testing could be determined. The TDR was then put to use in a laboratory program designed to investigate the response of loose gassy sand under static and cyclic loading. Because of the TDR measurements it was possible to determine the degree of saturation and void ratio of the gassy specimens. The TDR miniprobe proved to be accurate, simple to use, and inexpensive to build.Key words: time domain reflectometry, TDR, triaxial testing, gassy, unsaturated.

The Primary and Secondary Analysis of Uncertain Factors in Soil Thermal Properties for GSHP

2012 ◽  
Vol 614-615 ◽  
pp. 688-694 ◽  
Author(s):  
Yi Wang ◽  
Guo Min Shen
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Water Table ◽  
Unsaturated Soil ◽  
Solid Phase ◽  
Saturated Soil ◽  
Soil Thermal Conductivity ◽  
Saturation Degree ◽  
Soil Thermal Properties ◽  
Soil Solid Phase

In this paper, at first, an effective soil thermal conductivity model was established. Single factor regression analysis for 6 uncertain factors contained in the model was then conducted respectively. Finally, the primary and secondary characters of these uncertain factors were analyzed by using the orthogonal test. The analysis results show that the effective soil thermal conductivity has linear relationships with the saturation degree of unsaturated soil and the depth of water table and has power function relationships with other 4 uncertain factors; the porosity of unsaturated soil has the greatest effect on the effective soil thermal properties, followed by saturation degree of unsaturated soil, porosity of saturated soil, solid phase thermal conductivity of unsaturated soil, solid phase thermal conductivity of saturated soil and the depth of water table.

Permeability function for unsaturated soil

2018 ◽  
Vol 25 (1) ◽  
pp. 60-72 ◽  
Author(s):  
Tiande Wen ◽  
Longtan Shao ◽  
Xiaoxia Guo
Keyword(s):  
Unsaturated Soil ◽  
Permeability Function

TO DETERMINE THE PHYSICAL AND MECHANICAL PROPERTIES OF THE SOIL OF LANDSLIDE SLOPES FROM THE DEGREE OF POROSITY AND HUMIDITY

InterConf ◽  
2021 ◽  
pp. 917-933
Author(s):  
Аkbota Serikkyzy ◽  
A. Baimakhan ◽  
A. Makhanova ◽  
Baimakhan Baimakhan ◽  
G. Baimakhanova
Keyword(s):  
Mechanical Properties ◽  
Physical And Mechanical Properties ◽  
Local Stress ◽  
Saturated Soil ◽  
Degree Of Saturation ◽  
Stress Concentrations ◽  
Mountain Slope ◽  
Experimental Works ◽  
Water Saturated

The results of theoretical and experimental works devoted to the determination of the physical and mechanical properties of water–saturated soil are analyzed. On the basis of a comprehensive analysis, conclusions are formulated, and a method is proposed for determining the Young’s modulus and Poisson’s ratio for water-saturated soil, depending on humidity (degree of saturation) and porosity. Tables of data on the physical and mechanical properties of water–saturated soil are proposed. The study established the places of formation of local stress concentrations along the inclined layer. The values of dangerous stress concentrations found in various areas of the mountain slope that are vulnerable to collapse are shown in the tables.

Conservation of Mass

1997 ◽  
Author(s):  
David Jon Furbish
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Fluid Flow ◽  
Unsaturated Flow ◽  
Flow In Porous Media ◽  
Degree Of Saturation ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Conservation Of Mass ◽  
Special Case

The concept of conservation of mass holds a fundamental role in most problems in fluid physics. For a given problem this concept is cast in the form of an equation of continuity. Such an equation describes a condition—conservation of mass—that must be satisfied in any formal analysis of a problem. Thus an equation of continuity often is one of several complementary equations that are solved simultaneously to arrive at a solution to a flow problem, for example, the flow velocity as a function of coordinate position in a flow field. (Typically these complementary equations, as we will see in later chapters, involve conservation of momentum or energy, or both.) Although we did not explicitly use this idea in analyzing the one-dimensional flow problems at the end of Chapter 3, it turns out that continuity was implicitly satisfied in setting up each problem. We will return to these problems to illustrate this point. We will develop equations of continuity for three general cases: purely fluid flow, saturated single-phase flow in porous media, and unsaturated flow in porous media. The most general of the three equations is that for unsaturated flow, where pores are partially filled with the fluid phase of interest, such that the degree of saturation with respect to that phase is less than one. We will then show that this equation reduces, in the special case in which the degree of saturation equals one, to a simpler form appropriate for saturated single-phase flow. Then, this equation for saturated flow could be reduced further, in the special case in which the porosity equals one, to a form appropriate for purely fluid flow. For pedagogical reasons, however, we shall reverse this order and consider purely fluid flow first. In addition we will consider conservation of a solid or gas dissolved in a liquid, and take this opportunity to introduce Fick’s law for molecular diffusion. For simplicity we will consider only species that do not react chemically with the liquid, nor with the solid phases of a porous medium. Most of the derivations below are based on the idea of a small control volume of specified dimensions embedded within a fluid or porous medium.

An elasto-plastic model of unsaturated soil with an explicit degree of saturation-dependent CSL

2019 ◽  
Vol 260 ◽  
pp. 105240 ◽  
Author(s):  
Jian Li ◽  
Zhen-Yu Yin ◽  
Yu-Jun Cui ◽  
Kai Liu ◽  
Jian-Hua Yin
Keyword(s):  
Unsaturated Soil ◽  
Degree Of Saturation ◽  
Plastic Model

scholarly journals Experimental Investigation on Small-Strain Stiffness of Marine Silty Sand

2020 ◽  
Vol 8 (5) ◽  
pp. 360 ◽  
Author(s):  
Qi Wu ◽  
Qingrui Lu ◽  
Qizhou Guo ◽  
Kai Zhao ◽  
Pen Chen ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Void Ratio ◽  
Reduction Rate ◽  
Confining Pressure ◽  
Small Strain ◽  
Silty Sand ◽  
Bender Element ◽  
Small Strain Stiffness ◽  
Alternative State ◽  
State Index

The significance of small-strain stiffness (Gmax) of saturated composite soils are still of great concern in practice, due to the complex influence of fines on soil fabric. This paper presents an experimental investigation conducted through comprehensive bender element tests on Gmax of marine silty sand. Special attention is paid to the influence of initial effective confining pressure ( σ c 0 ′ ), global void ratio (e) and fines content (FC) on Gmax of a marine silty sand. The results indicate that under otherwise similar conditions, Gmax decreases with decreasing e or FC, but decreases with increasing FC. In addition, the reduction rate of Gmax with e increasing is not sensitive to σ c 0 ′ , but obviously sensitive to changes in FC. The equivalent skeleton void ratio (e*) is introduced as an alternative state index for silty sand with various FC, based on the concept of binary packing material. Remarkably, the Hardin model is modified with the new state index e*, allowing unified characterization of Gmax values for silty sand with various FC, e, and σ c 0 ′ . Independent test data for different silty sand published in the literature calibrate the applicability of this proposed model.

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