25 years of Geovert: Shotcrete Retaining Walls on the Seaford Rail Extension

Rail work is an important part of Geovert’s history, and the Seaford Rail Extension in Adelaide is one worth remembering as we reflect on 25 years in business. In 2013 Geovert built 13 retaining walls along the new 5.5-kilometre rail cutting and two stations, for the Thiess and McConnell Dowell joint venture.

Before construction began, Geovert spent several months in early contractor involvement with the project’s design engineers, Parsons Brinckerhoff, reworking the soil nail design using detailed quality records from Geovert’s recently completed ANZAC Highway/South Road underpass project. That data allowed the team to reduce the quantity of soil nailing necessary, improving the programme and driving down cost.

The retaining walls were built using a top-down method of soil nailing and shotcrete placement, and included complex vertical and inclined concave and convex panels at Seaford and Seaford Meadows stations, covering about 4,000 square metres with retained heights over 15 metres. The specification called for a stringent U3 steel trowel finish on the exposed slabs, a tight surface tolerance that is straightforward to achieve on a flat, formed slab but considerably harder on a sloped, curved shotcrete face built in three dimensions. Up to four drilling rigs and several shotcrete and steel fixing crews worked across multiple sites to deliver it.

The finish achieved was precise enough that it looks like precast concrete panelling rather than sprayed shotcrete, an outcome that earned Geovert an Award for Excellence in Concrete, Engineering Projects Category 2013, from the Concrete Institute of Australia’s South Australian branch.