Multi-scale characterization of swelling behaviour of compacted Maryland clay

Abstract

This paper presents a comprehensive experimental investigation on time-dependent swelling behaviour at both macroscale and microscale of a natural Australian expansive soil in compacted state. A number of one-dimensional swelling tests under different vertical pressures, different initial void ratios and initial water contents were performed. The characterization at macroscale was complemented by extensive microstructural investigations through mercury intrusion porosimetry and scanning electron microscope observation on both as-compacted and swollen specimens. The results were discussed at two different scales within a framework of double-porosity, which was finalized by linking the macrostructural–microstructural strains ratio with secondary swelling/compression coefficients. The multi-scale correlation appears to be largely independent of the specimen initial conditions. The study showed that the secondary swelling and primary swelling are governed by the same factors and that secondary swelling takes place mainly in macropores, of which the change magnitude depends on the level of confinement applied. The microstructural investigations show that swelling is accompanied by significant microfabric changes.