Role of unsaturated permeability function in seepage analyses

2015 ◽  
pp. 393-399
Author(s):  
A Rahimi ◽  
H Rahardjo ◽  
E Leong
Keyword(s):  
Permeability Function ◽  
Unsaturated Permeability ◽  
Seepage Analyses

scholarly journals Examination of the estimation of relative permeability for unsaturated soils

2015 ◽  
Vol 52 (12) ◽  
pp. 2077-2087 ◽  
Author(s):  
Feixia Zhang ◽  
D.G. Fredlund
Keyword(s):  
Lower Limit ◽  
Unsaturated Soils ◽  
Integral Formula ◽  
Characteristic Curve ◽  
Soil Conditions ◽  
Mathematical Algorithm ◽  
Soil Systems ◽  
Permeability Function ◽  
Unsaturated Permeability ◽  
Flexible Integration

The unsaturated permeability function is an important soil property function used in the numerical modeling of saturated–unsaturated soil systems. The permeability function is generally predicted by integrating along the soil-water characteristic curve (SWCC) starting at saturated soil conditions. The integration is based on a particular integral formula. The Fredlund–Xing–Huang permeability function is a flexible integration technique used for calculating the unsaturated permeability function. The original permeability theory published by Fredlund, Xing, and Huang in 1994 specified that the air-entry value (AEV), ψaev, be used as the lower limit of the integration when calculating the permeability function. However, as there was no analytical procedure available for the calculation of the AEV on the SWCC, it became common practice to start the integration procedure from a value near zero. The assumption was made that the error associated with starting the integration from an arbitrary low value was minimal. While this might be the case in some situations, the error can be quite substantial in other situations. This paper undertakes a study of the effect of the lower limit of integration on the calculation of the permeability function. Comparisons are made between starting the integration from various values below the AEV and starting the integration from the calculated AEV, ψaev. A mathematical algorithm is also proposed for the calculation of the AEV for integration purposes. The results show that the relative coefficient of permeability can be significantly underestimated when the lower limit of integration is smaller than the AEV. The recommendation is that the AEV always be used as the lower limit of integration in the Fredlund–Xing–Huang permeability equation.

scholarly journals New approach to improve soil-water characteristic curve to reduce variation in estimation of unsaturated permeability function

2016 ◽  
Vol 53 (4) ◽  
pp. 717-725 ◽  
Author(s):  
Arezoo Rahimi ◽  
Harianto Rahardjo
Keyword(s):  
Soil Water ◽  
Distribution Curve ◽  
Characteristic Curve ◽  
New Approach ◽  
Soil Water Characteristic Curve ◽  
Permeability Function ◽  
Wide Range ◽  
Unsaturated Permeability ◽  
Complete Measurement ◽  
Data Points

The unsaturated permeability function is often estimated from the soil-water characteristic curve (SWCC) of a soil. A complete SWCC measurement can improve the estimation of the unsaturated permeability function. In most laboratories, the SWCC can be measured up to a suction of 100 kPa using a Tempe cell. However, complete measurement of the SWCC is an expensive and time-consuming task. Therefore, this paper presents a new approach to estimate SWCC data points beyond 100 kPa suction to complement the SWCC measured up to a suction of 100 kPa. The new SWCC is then used to estimate the unsaturated permeability function. The proposed approach uses knowledge of the grain-size distribution curve and measured SWCC data at 100 kPa suction to estimate the SWCC data points beyond 100 kPa suction. To verify the proposed procedure, SWCC tests were conducted over a wide range of suctions for coarse kaolin and a triaxial permeameter system was used to directly measure unsaturated permeability of the coarse kaolin. The proposed procedure is found to reduce the variation between unsaturated permeability functions estimated by various estimation models.

Prediction and modeling of permeability function and its application to the evaluation of breakthrough suction of a two-layer capillary barrier

2017 ◽  
Vol 54 (6) ◽  
pp. 778-788 ◽  
Author(s):  
W.M. Yan ◽  
C.F. Chiu ◽  
Ka-Veng Yuen
Keyword(s):  
Joint Probability ◽  
Water Retention Curve ◽  
Capillary Barrier ◽  
Empirical Formulas ◽  
Deterministic Method ◽  
Retention Curve ◽  
Permeability Function ◽  
Unsaturated Permeability ◽  
Silty Loam ◽  
Joint Probability Density

Different empirical formulas have been proposed to describe the water retention curve (WRC) and relative permeability (kr) of soils. This paper presents a Bayesian framework that evaluates not only the most probable empirical fitting constants, but also their joint probability density function. A dataset containing two soil classes — sand and silty loam — compiled from the UNSODA database is used for illustration. First, model constants of the van Genuchten’s WRC formula are calibrated and subsequently used to predict kr of the studied soils using two existing formulas based on Mualem’s and Burdine’s models. The best estimated kr in both formulas is found to skew towards the lower side of the measurement. Then, a new three-parameter empirical formula is proposed to describe kr with suction while the model constants are calibrated from the permeability data. Using the proposed framework, the statistical distribution of kr and subsequently the unsaturated permeability (kunsat), as a function of suction, can be obtained. The results are then applied to a hypothetical two-layer capillary barrier composed of soils of the compiled dataset to determine the breakthrough suction (ψBT) of the barrier. The proposed Bayesian approach gives a probabilistic distribution of ψBT instead of a single value in the traditional deterministic method.

scholarly journals Influence of Degree of Compaction on Unsaturated Hydraulic Properties of a Compacted Completely Decomposed Granite

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-9 ◽  
Author(s):  
Rui Chen ◽  
Runqiang Tan ◽  
Zhongkui Chen ◽  
Yang Ping ◽  
Zhen Mei
Keyword(s):  
Hydraulic Properties ◽  
Prediction Models ◽  
Mercury Intrusion Porosimetry ◽  
Characteristic Curve ◽  
Southeastern China ◽  
Permeability Function ◽  
Unsaturated Permeability ◽  
Decomposed Granite ◽  
Engineering Projects ◽  
Completely Decomposed Granite

It is crucial to understand hydraulic properties, i.e., soil-water characteristic curve (SWCC) and unsaturated permeability function (UPF), of completely decomposed granite (CDG) for relevant engineering projects in southeastern China. Previous studies mainly focused on SWCCs of CDG, whereas UPFs of CDG have not yet been well understood. In this study, the effects of the degree of compaction (DOC) on SWCCs and UPFs of CDG were investigated based on experiments where suction range was from 0 to 500 kPa. The microstructure of soil specimens was then analyzed by mercury intrusion porosimetry (MIP). Furthermore, the UPFs of CDG under different values of DOC were calculated using four prediction models and compared with experimental data. Results showed that the pore volume of specimens at higher DOC was smaller than that at lower DOC, and there were more macropores observed in specimens at lower DOC. Meanwhile, it was found that increasing compaction effort produced negligible influence on the volume of micropores. When the suction was less than 100 kPa, the permeability was reduced with the increase in DOC, due to the decrease of macropore volume. However, the influence of DOC on SWCCs and UPFs became marginal when the suction exceeded 100 kPa. The Fredlund and Xing model provided the best prediction of UPF among the four models when suction was smaller than air entry value (AEV). It is suggested that these models could be improved to capture UPFs at higher suctions than AEV by considering suction-induced volume contraction.

Role of dactinomycin in the improved survival of children with Wilms' tumor

JAMA ◽  
1966 ◽  
Vol 195 (12) ◽  
pp. 1005-1009 ◽  
Author(s):  
D. J. Fernbach
Keyword(s):  
Wilms Tumor

Role of the allergist in diagnosis and management of patients with uveitis

JAMA ◽  
1966 ◽  
Vol 195 (3) ◽  
pp. 167-172 ◽  
Author(s):  
T. E. Van Metre
Keyword(s):  
Diagnosis And Management

The power of norms to sway fused group members

2018 ◽  
Vol 41 ◽  
Author(s):  
Winnifred R. Louis ◽  
Craig McGarty ◽  
Emma F. Thomas ◽  
Catherine E. Amiot ◽  
Fathali M. Moghaddam
Keyword(s):  
Evolutionary Anthropology ◽  
Normative Systems ◽  
Violent Extremism ◽  
Identity Fusion ◽  
Group Members

AbstractWhitehouse adapts insights from evolutionary anthropology to interpret extreme self-sacrifice through the concept of identity fusion. The model neglects the role of normative systems in shaping behaviors, especially in relation to violent extremism. In peaceful groups, increasing fusion will actually decrease extremism. Groups collectively appraise threats and opportunities, actively debate action options, and rarely choose violence toward self or others.

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