Field and laboratory investigation of an expansive soil site in Melbourne

Expansive soils undergo heave and settlement due to soil moisture changes, causing differential movement to light weight structures built on them. These movements may be significant when extreme weather conditions such as prolonged droughts are encountered. Indeed, there have been major concerns regarding footing movements and cracks in houses in Victoria following the breaking of the last prolonged drought experienced in the late 90s to early 2000s.

As part of an ongoing research project at Swinburne University of Technology on damage to residential structures due to ground movements, a field site was established in a western suburb of Melbourne. In situ soil moisture variation and corresponding ground movements are monitored using a neutron moisture probe and magnetic extensometers respectively. In addition, various laboratory experiments including soil classification, suction, swell and shrinkage were carried out on both disturbed and undisturbed soil samples collected from the field site. Suction variations of undisturbed soil along with moisture content have been measured using miniature tensiometers and a Chilled Mirror Hygrometer to develop the Soil Water Characteristic Curve (SWCC). Atterberg limit tests and particle size distribution tests have also been carried out at different depths to classify the soil.

This paper discusses results from both the field and the laboratory investigations. In addition, it presents mechanical and hydraulic properties of the field soil that can be used in numerical analyses.