American Society of Civil Engineers

New Soil-Water Characteristic Curve and Its Performance in the Finite-Element Simulation of Unsaturated Soils

by Shada H. Krishnapillai, M.ASCE, (Graduate Student, Dept. of Civil Engineering, Clemson Univ., Clemson, SC 29634 E-mail: and Nadarajah Ravichandran, Ph.D., (corresponding author), M.ASCE, (Assistant Professor, Dept. of Civil Engineering, Clemson Univ., Clemson, SC 29634 E-mail:

International Journal of Geomechanics, Vol. 12, No. 3, May/June 2012, pp. 209-219, (doi:

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Document type: Journal Paper
Abstract: Among the many constitutive equations, the moisture-suction relationship, also known as the soil-water characteristic curve (SWCC), is one of the important relationships needed for modeling the dynamics of unsaturated soils using the finite-element method. In this study, a new SWCC equation is developed that uses four fitting parameters including the maximum possible suction. The new model predicts the experimental data of various soils well for a wide range of degrees of saturation (DOS), especially in high suction (above 10,000 kPa). Predicting the higher suction at low DOS is one of the deficiencies of the widely used Brooks and Corey, van Genuchten, and Fredlund and Xing models. The numerical stability and performance of the proposed, and other widely used models, are investigated by implementing these models within in a simplified finite-element program for the dynamics of unsaturated soil and simulating static and dynamic problems. For the midrange DOS, all of the aforementioned models predict similar responses. However, at low DOS the new model predicts the suction variations well compared with the other models.

ASCE Subject Headings:
Finite element method
Unsaturated soils
Soil water

Author Keywords:
Soil-water characteristic curve
Unsaturated soils
SWCC for low degree of saturation
General equation for soil-water characteristic curve
Comparison of soil-water characteristic curves