American Society of Civil Engineers


Coupled Hydro-Mechanical Elastoplastic Constitutive Model for Unsaturated Sands and Silts. I: Formulation


by Chunyang Liu, Ph.D., (corresponding author), M.ASCE, (Assistant Professor, Dept. of Civil and Environmental Engineering, Univ. of South Carolina, 300 Main St., Columbia, SC 29208; formerly, Research Associate, School of Civil Engineering and Environmental Science, Univ. of Oklahoma, 202 W. Boyd St., Room 334, Norman, OK 73019 E-mail: liuch@cec.sc.edu) and Kanthasamy K. Muraleetharan, Ph.D., M.ASCE, (Kimmell-Bernard Chair in Engineering and David Ross Boyd and Presidential Professor, School of Civil Engineering and Environmental Science, Univ. of Oklahoma, 202 W. Boyd St., Room 334, Norman, OK 73019 E-mail: muralee@ou.edu)

International Journal of Geomechanics, Vol. 12, No. 3, May/June 2012, pp. 239-247, (doi:  http://dx.doi.org/10.1061/(ASCE)GM.1943-5622.0000146)

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Document type: Journal Paper
Abstract: Unsaturated soils are three-phase porous media consisting of a solid skeleton, pore water, and pore air. The behavior of unsaturated soils is strongly influenced by the matric suction (pore air pressure minus the pore water pressure). Soil water characteristic curves (SWCCs) describe the relationship between matric suction and water content in unsaturated soils and, therefore, capture the hydro-behavior of soils. SWCCs show hysteretic behavior that not only depends on the wetting or drying history of the soil, but also on the stress-strain history (mechanical behavior) of a soil. The hydro-behavior of unsaturated soils, on the other hand, influences the mechanical behavior through matric suction. To predict the behavior of unsaturated soils, a hysteretic SWCC model is proposed based on the bounding surface plasticity concept. The model for hysteretic SWCCs is then incorporated into a constitutive model for unsaturated sands and silts in the general stress space. The resulting model is a comprehensive constitutive model that accounts for the coupling effects between hydro- and mechanical behavior of unsaturated sands and silts in the general stress space. The numerical integration of the constitutive equations and model calibration and validation are presented in a companion paper.


ASCE Subject Headings:
Unsaturated soils
Constitutive models
Elastoplasticity
Coupling
Soil water
Silts

Author Keywords:
Unsaturated soils
Constitutive model
Elastoplasticity
Hydro-mechanical coupling
Soil water characteristic curves