Unsaturated Soil Analysis in Bendigo

Bendigo sits on ancient, deeply weathered profiles. The clays here are stiff when dry but soften fast with rain. That shift from dry to wet changes everything. Unsaturated soil analysis captures that behavior. It measures suction, moisture content, and how the ground holds together when it is not fully saturated. For a block of townhouses on the northern slopes, we paired this with a permeability field test to map drainage paths. The results told us where the ground would swell and where it would settle. In Bendigo, assuming saturated conditions is a shortcut to trouble. The real soil lives in that in-between state.

In Bendigo, assuming saturated conditions is a shortcut to trouble. The real soil lives in that in-between state.

Methodology and scope

Local considerations

A two-story commercial building in the Bendigo CBD had a slab that heaved 80 mm after three wet winters. The original design used saturated soil parameters. The unsaturated analysis showed the clay had a high collapse potential on wetting. The slab was under-reinforced. We now recommend unsaturated analysis for any site with reactive clay. The cost of a retrofit is ten times the cost of the test. In Bendigo, ignoring the unsaturated state means accepting differential movement.

Technical parameters

Applicable standards

AS 1726 – Geotechnical Site Investigations, AS 1289 – Determination of the Soil Water Characteristic Curve, AS/NZS 1170.0 – Structural Design Actions

Frequently asked questions