Geotechnical Engineering Aspects of the Construction of the Barcoo Outlet

Dr. Peter Mitchell

The Barcoo stormwater outlet project involved the construction of a cut-and-cover concrete culvert from the waters of the Patawalonga, through the sand dunes at West Beach, to a distance of around 200 m out into the Gulf St Vincent. The precast concrete culvert allows the movement of stormwater from the Patawalonga out to the Gulf. The project represented a major civil engineering undertaking involving the construction of the 6 m high culvert under a public road, under 10 m high sand dunes, and about 8 m under the sea bed. Geotechnical issues faced by the construction included dewatering the highly permeable sand deposits, slope stability of deep cuts through loose, clean sand, bearing capacity and settlement issues for the culvert, sheet piling stability, piping of groundwater, grouting issues, and stabilisation using geotextiles. In his talk, Peter described the geotechnical conditions encountered along the alignment of the culvert and the implications of the ground conditions on the construction. Dr Mitchell will be well known to most AGS members, having presented more than 30 talks to the South Australian Chapter over many years.

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