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Saturday, October 31, 2009 |
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Piling for Brickmakerskloof Bridge, Bakens Valley – Port Elizabeth
:: News
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Source: Petrus van Straten
In August 2009 Stefanutti Stocks Geotechnical (Pty) Ltd was appointed to carry out the piling which provided founding for the new proposed road-over-river bridge, spanning across the Sharks River in the Brickmakerskloof area, Port Elizabeth. The three-month project is being undertaken for the Nelson Mandela Bay Municipality.
The existing bridge was closed for traffic in 2006, due to severe flood damage, with the new proposed bridge and access road replacing the existing infrastructure.
A total of 48 piles (14 at each of the two abutments and ten at each of the two piers) are currently being installed.
To complicate matters 70% of the piles are being installed as 1:8 raking piles.The piles are formed by means of augering and coring through alluvium, medium hard rock (25MPa) and hard rock (100 MPa). This combined with severe groundwater seepage and the occurrence of alluvium gravels and boulders, results in severe sidewall collapse.
“In order to address the challenging geological aspects of the project,” says Petrus van Straten, contracts director, “we priced the works with an alternative for the installation of 750mm diameter temporary-cased auger cast in-situ piles with an average pile drilled length of 9m”.The bottom of the pile holes are cleaned thoroughly by a cleaning bucket, followed by airlifting. Concrete is placed by means of a tremie whilst the temporary casings are being extracted.
Shear dowels are being installed through pre-placed steel tubes to provide additional scour resistance.
Quality control measures include carrying out two compressive load tests, load testing the piles to 1.5 times the design working load. In addition, integrity testing by means of the CSL method is being carried out to confirm concrete shaft integrity.
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