Melbourne sits on a mix of Quaternary basalts, Silurian mudstones and Quaternary alluvium, so slope behaviour varies block by block. In our lab, we apply AS 4678-2002 (Earth Retaining Structures) and AS 1726-2017 (Geotechnical Site Investigations) as the baseline for every stability assessment. For a deep cut in the Yarra Valley clays, for instance, we first run a resistivity survey to map subsurface layering — that data feeds directly into our limit-equilibrium models. The same approach applies to the steep coastal bluffs around the Mornington Peninsula, where we combine field mapping with laboratory shear-strength testing to define realistic failure surfaces. Every Melbourne project gets a city-specific factor of safety, never a generic default.
In Melbourne, the clay crust can lose 40% of its undrained strength when saturated — seasonal moisture is the real trigger for slope failure.