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Piling to the Swakopmund River Bridge

The piling to the Swakopmund River Bridge (that formed part of the upgrade of the railway line running between Walvis Bay and Kranzberg) was undertaken by the Stefanutti Stocks Geotechnical Discipline for China Gezhouba Investment Group (Namibia) in 17 working days during the month of June 2021

Background: The Swakopmund River Bridge piling project formed part of the upgrade of a 210km long rail link in Namibia. To accommodate the replacement of the existing forty-metre-long steel-structure bridge (that would be lifted off its position and replaced by a new upgraded steel structure) an additional pier was introduced mid-way.

The Project Scope

The scope included the piling for the new bridge pier, founded on bed-rock to an average depth of 7,5m below ground.

The new pier consisted of six piles – three either side of the current structure as the overhead room under the existing steel bridge made it impossible to drill and build a foundation right beneath it. The new pier was centred below the current bridge, with the three piles one one side linked to the three on the other side via a pile cap.

All six piles were founded by oscillating a temporary casing to rock level, which would hold back the very loose river sand and alluvium material present in the Namib Desert. Once the temporary casing was seated in the bedrock, the team were able to form rock sockets of up to 2.5m in Pegmatite, classified as Very Hard Rock Class R5. Once the sockets were cleaned, a permanent galvanised 1.6mm liner was installed along with the reinforcing.

The river was diverted for the duration of the project, however, due to the river flowing through the sands below, the concrete was cast underwater via the tremie method. Once the concrete pile shafts were cast and formed, the temporary casings were extracted to reveal the complete pile. Finally, to ensure a good quality product with no anomalies, all six piles were sonic logged.

The project was successfully completed, delivered to specifications, and achieved a Lost Time Injury Frequency of zero.

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Stefanutti Stocks: Geotechnical Discipline

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