Abstract
This paper proposes a new water retention model for unsaturated soils, which takes into account capillary condensation of adsorbed water. In the proposed water retention model, the degree of saturation of a soil is separated into that based on capillary water and that based on adsorbed water. Through the analysis of a partially saturated two-cylinder system, a new shear strength criterion for unsaturated soils is proposed, in which only the degree of saturation based on capillary water contributes to the variation of shear strength with suction. The proposed shear strength criterion is justified against thermodynamic principles. The proposed strength criterion is compared against existing criteria in the literature, which shows that it provides a much improved prediction of the experimental data, for a wide range of suction values.
Highlights
A number of shear strength criteria for unsaturated soils have been proposed in the literature during past three decades or so
The degree of saturation that can be obtained from the water retention curve for a given suction has been widely embedded into strength criteria for unsaturated soils, such as [1]; [2]; [3] and [4]; etc
Capillary water exists among soil particles and the pressure of capillary water affects the contact stress ( ') among soil particles [3], [5]
Summary
A number of shear strength criteria for unsaturated soils have been proposed in the literature during past three decades or so. The contribution from adsorbed water to the shear strength of the soil is very limited [6,7,8,9]. In principle, this is because adsorbed water wraps the surface of each soil particle and the pressure of adsorbed water almost does not affect the contact stress ( ') among soil particles. The objective of this study is to derive the shear strength criterion for unsaturated soils by considering that pore water consists of capillary water and adsorbed water. The proposed model is compared with existing shear strength criteria, against experimental data in the literature
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