Statistical assessment of soil-water characteristic curve models for geotechnical engineering

2001 ◽  
Vol 38 (6) ◽  
pp. 1297-1313 ◽  
Author(s):  
W Scott Sillers ◽  
Delwyn G Fredlund
Keyword(s):  
Soil Water ◽  
Akaike Information Criterion ◽  
Characteristic Curve ◽  
Information Criterion ◽  
Soil Suction ◽  
Data Sets ◽  
Empirical Equations ◽  
Soil Water Characteristic Curve ◽  
The Relationship ◽  
Best Fit

A number of empirical equations have been proposed for the soil-water characteristic curve. A nonlinear, least squares method was used to determine best-fit parameters for several empirical equations that were best-fit to 230 water content versus soil suction data sets. In addition, two proposed correction methods to accommodate high soil suctions up to 1 000 000 kPa were applied to the various soil-water characteristic curve equations. The data sets of water content versus soil suction were arranged into one of the USDA soil classifications based on their relative amounts of sand, silt, and clay (only eight soil classifications had sufficient data for later analysis). The quality of fit for each model was compared using the Akaike Information Criterion. A series of conclusions were arrived at regarding (i) the relationship between two- and three-parameter equations, (ii) the relationship between exponential and sigmoidal type equations, and (iii) the value of correction factors for the high soil suction range.Key words: soil-water characteristic curve, unsaturated soil, soil suction, regression analysis, SWCC models, Akaike Information Criterion.

Soil Water Characteristic Curve and its Applications in Tunnel

2011 ◽  
Vol 261-263 ◽  
pp. 1039-1043
Author(s):  
Yu You Yang ◽  
Qin Xi Zhang ◽  
Gui He Wang ◽  
Jia Xing Yu
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Land Subsidence ◽  
Unsaturated Soil ◽  
Characteristic Curve ◽  
Tunnel Construction ◽  
Coupling Theory ◽  
Engineering Analysis ◽  
Soil Water Characteristic Curve ◽  
The Relationship

A soil water characteristic curve (SWCC) can describe the relationship between unsaturated soil matric suction and water content. By analyzing and researching the test data of the soil water characteristic curve researchers can initially establish the SWCC equation and apply this equation to the actual engineering analysis. In another words, this article is based on the fluid-solid coupling theory of unsaturated soil used to analyze and study the problem of land subsidence caused by tunnel construction. Numerical calculations show that the coupling results agree well with the measured curve works.

scholarly journals Performance Evaluation of Four-Parameter Models of the Soil-Water Characteristic Curve

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Siti Jahara Matlan ◽  
Muhammad Mukhlisin ◽  
Mohd Raihan Taha
Keyword(s):  
Soil Water ◽  
Characteristic Curve ◽  
Data Sets ◽  
Modified Model ◽  
Soil Water Characteristic Curve ◽  
Geoenvironmental Engineering ◽  
Wide Range ◽  
Soil Water Characteristic Curves ◽  
Model Equations ◽  
Exponential Variable

Soil-water characteristic curves (SWCCs) are important in terms of groundwater recharge, agriculture, and soil chemistry. These relationships are also of considerable value in geotechnical and geoenvironmental engineering. Their measurement, however, is difficult, expensive, and time-consuming. Many empirical models have been developed to describe the SWCC. Statistical assessment of soil-water characteristic curve models found that exponential-based model equations were the most difficult to fit and generally provided the poorest fit to the soil-water characteristic data. In this paper, an exponential-based model is devised to describe the SWCC. The modified equation is similar to those previously reported by Gardner (1956) but includes exponential variable. Verification was performed with 24 independent data sets for a wide range of soil textures. Prediction results were compared with the most widely used models to assess the model’s performance. It was proven that the exponential-based equation of the modified model provided greater flexibility and a better fit to data on various types of soil.

Model for the prediction of shear strength with respect to soil suction

1996 ◽  
Vol 33 (3) ◽  
pp. 379-392 ◽  
Author(s):  
S K Vanapalli ◽  
D G Fredlund ◽  
D E Pufahl ◽  
A W Clifton
Keyword(s):  
Shear Strength ◽  
Soil Water ◽  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Characteristic Curve ◽  
Experimental Studies ◽  
Matric Suction ◽  
Glacial Till ◽  
Soil Suction ◽  
Soil Water Characteristic Curve

Experimental studies on unsaturated soils are generally costly, time-consuming, and difficult to conduct. Shear strength data from the research literature suggests that there is a nonlinear increase in strength as the soil desaturates as a result of an increase in matric suction. Since the shear strength of an unsaturated soil is strongly related to the amount of water in the voids of the soil, and therefore to matric suction, it is postulated that the shear strength of an unsaturated soil should also bear a relationship to the soil-water characteristic curve. This paper describes the relationship between the soil-water characteristic curve and the shear strength of an unsaturated soil with respect to matric suction. Am empirical, analytical model is developed to predict the shear strength in terms of soil suction. The formulation makes use of the soil-water characteristic curve and the saturated shear strength parameters. The results of the model developed for predicting the shear strength are compared with experimental results for a glacial till. The shear strength of statically compacted glacial till specimens was measured using a modified direct shear apparatus. Specimens were prepared at three different water contents and densities (i.e., corresponding to dry of optimum, and wet of optimum conditions). Various net normal stresses and matric suctions were applied to the specimens. There is a good correlation between the predicted and measured values of shear strength for the unsaturated soil. Key words: soil-water characteristic curve, shear strength, unsaturated soil, soil suction, matric 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.

The Development of a One-Parameter Model for the Soil-Water Characteristic Curve in Loess Gully Regions

2012 ◽  
Vol 256-259 ◽  
pp. 488-493
Author(s):  
Xiao Yu Song ◽  
Huai You Li ◽  
Wen Juan Shi
Keyword(s):  
Soil Water ◽  
Hydraulic Properties ◽  
Characteristic Curve ◽  
Soil Samples ◽  
Soil Hydraulic Properties ◽  
Logarithmic Model ◽  
Soil Water Characteristic Curve ◽  
Soil Water Characteristic Curves ◽  
Best Fit ◽  
Gardner Model

It is important to understand soil hydraulic properties in order to predict the movement of water and solutes such as pollutants. To this end, 55 soil samples were collected from different areas of the Nanxiaohegou basin and used to generate soil-water characteristic curves. These were then fitted using the power-, exponential-, and logarithmic versions of the Gardner model; the logarithmic model yielded the best fit overall. The logarithmic model was further simplified to yield a one-parameter model for estimating the soil-water characteristic curve within the basin, and it was demonstrated that the value of the single parameter is dependent on the topography and usage of the land.

Significance of Soil Suction and Soil Water Characteristic Curve Parameters

2005 ◽  
Vol 28 (1) ◽  
pp. 11845 ◽  
Author(s):  
L David Suits ◽  
TC Sheahan ◽  
GL Sivakumar Babu ◽  
J Peter ◽  
MD Mukesh ◽  
...  
Keyword(s):  
Soil Water ◽  
Characteristic Curve ◽  
Soil Suction ◽  
Soil Water Characteristic Curve

scholarly journals A New Soil-Water Characteristic Curve Model for Unsaturated Loess Based on Wetting-Induced Pore Deformation

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Yuwei Zhang ◽  
Zhanping Song ◽  
Xiaolin Weng ◽  
Yongli Xie
Keyword(s):  
Soil Water ◽  
Characteristic Curve ◽  
Shift Factor ◽  
Model Parameters ◽  
Average Pore ◽  
Average Pore Radius ◽  
New Model ◽  
Soil Water Characteristic Curve ◽  
Unsaturated Loess ◽  
The Relationship

The soil-water characteristic curve (SWCC) is the basis for describing seepage, strength, and constitutive model of unsaturated soil. The existing SWCC models do not work accurately for evaluating loess, because they do not consider the pore deformation that is induced by wetting. The present study develops a new SWCC model for unsaturated loess. The model considers the effect of wetting-induced pore deformation (WIPD) on the SWCC. The new model includes 6 parameters, which could be confirmed by laboratory tests. The pore volume function (PVF) was described by the WIPD. The shift factor ξ1i and the compression factor ξ2i were introduced into the model. The relationship between the void ratio e and ξ1i and ξ2i was established using the average pore radius. The new SWCC model for saturated loess was improved based on the classical van Genuchten (V-G) model. If the WIPD had not been considered, the new model would regress into the classical V-G model. SWCC tests of unsaturated loess with different void ratios were carried out to verify the new model. The model parameters were calibrated in the original state, and the SWCCs of different void ratios were predicted by the new model and found to be in good agreement with the test results.

Study on the Test of Soil Water Characteristic Curve

2011 ◽  
Vol 261-263 ◽  
pp. 1094-1098
Author(s):  
Yu You Yang ◽  
Qin Xi Zhang ◽  
Gui He Wang ◽  
Chen Liu
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Unsaturated Soil ◽  
Characteristic Curve ◽  
Mathematic Model ◽  
Matric Suction ◽  
Engineering Properties ◽  
Soil Water Characteristic Curve ◽  
Van Genuchten Model ◽  
The Relationship

The test of soil water characteristic curve (SWCC) and its mathematic model are present. The SWCC can describe the relationship between unsaturated soil matric suction and water content. Matric suction is an important parameter to address when studying the engineering properties of unsaturated soil. And while the measurement of substrate attraction is a very difficult issue, it is also one of the biggest obstacles in the engineering applications of unsaturated soil. By analyzing and researching the test data of SWCC researchers can initially establish the mathematic model which is the SWCC equation. The Van Genuchten model and the Fredlund and Xing model were used to simulate better the changes between the volume water content and the matric suction. Predictions were compared with experimental results to determine the simulation capability of the model for the soil of Beijing.

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