ABSTRACT
The presence of two pore fluids in unsaturated soils leads to substantial behavioural differences between unsaturated and saturated soils. Many researchers have examined unsaturated soil behaviour in laboratory experiments (Sivakumar 1993), field studies (Springman et al. 2003), numerical analysis (Georgiadis et al. 2003) and constitutive modelling work (Wheeler & Sivakumar 1995). Previous work has shown a bimodal structure in unsaturated compacted clays consisting of groups of individual particles forming aggregates and these aggregates form an overall structure (Lloret et al. 2003). Wetting of unsaturated soils produces a combination of aggregate swelling, loss of frictional resistance at aggregate contacts and aggregate deformation (Thom et al. 2007). Sivakumar (2005) showed that swelling of heavily compacted clay was significantly influenced by the initial density. Figure 1 shows the increase in specific volume plotted against suction for samples with different initial densities. The graph shows that under wetting heavily compacted soil produced greater swelling than lightly compacted kaolin. This work shows the importance of the initial compaction effort on the volume change behaviour of compacted fills.
