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.

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.

scholarly journals Estimation of air permeability function from soil-water characteristic curve

2019 ◽  
Vol 56 (4) ◽  
pp. 505-513
Author(s):  
Qian Zhai ◽  
Harianto Rahardjo ◽  
Alfrendo Satyanaga
Keyword(s):  
Distribution Function ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Soil Water ◽  
Unsaturated Soil ◽  
Characteristic Curve ◽  
Air Permeability ◽  
Size Distribution Function ◽  
Soil Water Characteristic Curve ◽  
Permeability Function

The multiphase flow (including liquid flow and air flow) in unsaturated soil is related to many engineering problems such as contaminant transport, rainwater infiltration, and soil-water evaporation. It is proven that water flow in unsaturated soil can be estimated using the concept of the pore-size distribution function. Many models have been proposed to estimate the water flow or water permeability function, kw, from the soil-water characteristic curve (SWCC). On the other hand, a limited model has been proposed to estimate the air flow or air permeability function, ka, from the SWCC. Most of the models used for the estimation of the air permeability functions are empirical, and they are dependent on the empirical parameters. In this paper, the relative air coefficient of permeability was estimated using the concept of the pore-size distribution function. In the method proposed in this paper, no empirical parameters were adopted, and the estimation results purely depended on the soil-water characteristic curve. The proposed method was verified against experimental data from published literature.

scholarly journals Prediction of soil water characteristic curve using artificial neural network: a new approach

2018 ◽  
Vol 162 ◽  
pp. 01014
Author(s):  
Abdul-Kareem Esmat Zainal ◽  
Shaimaa Hasan Fadhil
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Soil Properties ◽  
Soil Water ◽  
Unsaturated Soil ◽  
Characteristic Curve ◽  
New Approach ◽  
Soil Water Characteristic Curve ◽  
Important Relationship ◽  
Artificial Neural

Soil-Water Characteristic Curve (SWCC) is an important relationship between matric suction and volumetric water content of soils especially when dealing with unsaturated soil problems, these problems may include seepage, bearing capacity, volume change, etc. where the matric or total suction may have a considerable effect on unsaturated soil properties. Obtaining an accurate SWCC for a soil could be cumbersome and sometimes it is time consuming and needs effort for some soils, either through laboratory tests or through field tests. Accurate prediction of this curve can give more precise expectations in design or analysis that include some unsaturated soil properties, which can save more effort and time. This work will concentrate on proposing a new approach for determining the SWCC using Artificial Neural Network (ANN) depending on some soil properties (air-entry point and residual degree of saturation) through computer software MatLab as a tool for ANN. The new approach is to plot the SWCC curve points instead of obtaining the parameters used in Brooks and Corey (BC) Model (1964), van Genuchten (VG) Model (1980), or Fredlund and Xing (FX) Model (1994). Results showed close agreement in determination of the SWCC by verification of the ANN results with an additional curve sample.

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.

Effect of bimodal soil-water characteristic curve on the estimation of permeability function

2017 ◽  
Vol 230 ◽  
pp. 142-151 ◽  
Author(s):  
Qian Zhai ◽  
Harianto Rahardjo ◽  
Alfrendo Satyanaga ◽  
Priono
Keyword(s):  
Soil Water ◽  
Characteristic Curve ◽  
Soil Water Characteristic Curve ◽  
Permeability Function

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.

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