Experimental Study of Small Strain Stiffness of Unsaturated Silty Clay

Abstract

The small strain stiffness of saturated soils has been extensively studied in the past decades, and therefore the literature database of small strain stiffness of different soils is vast and contains the necessary information for development and calibration of numerical models. However, there is a lack of data of small strain stiffness in case of unsaturated soils. This paper presents the stiffness of unsaturated silty clay in both small and very small strain regions.

The laboratory tests were carried out in the double-walled cell triaxial apparatus with HAEV (high air entry value) ceramic disk mounted in the base pedestal, and the axis translation technique was used. The reconstituted specimens of 70 mm in diameter were tested and the very small strain stiffness was measured by bender elements, while in the case of the small strain stiffness measurement, the submersible LVDTs were used. Different stress paths were applied, and every stress change was followed by an equalization period. Subsequently, the very small strain shear modulus (G₀) was determined by bender elements, and its decay in the small strain range was determined using short shear probes of up to 30 kPa.