The coastal plain geology of Adelaide presents a unique set of challenges for tunnelling. Unlike the hard rock you find in the eastern states, much of the city’s subsurface is dominated by the stiff, highly reactive Hindmarsh Clay and saturated Quaternary alluvium along the River Torrens corridor. This means a standard tunnel design approach rarely works here—you need a soft ground tunnel analysis that accounts for low stand-up times, swelling pressures, and groundwater inflows before the first cut is made. Our team has been involved in ground characterisation for infrastructure projects across the Adelaide metropolitan area, from the southern suburbs near Hallett Cove to the inner-north renewal zones, where the Keswick Clay transitions into more variable alluvial deposits. Understanding how these materials behave under unloading is the difference between a controlled excavation and a costly collapse.
A Su of 25 kPa in the Adelaide alluvium means your tunnel face needs active support within hours—there is no room for conservative, slow excavation cycles.
