Construction World July 2017

Pier 2 piles trimmed in preparation for pile cap construction.

Franki Africa is part of the Keller group, the largest independent geotechnical contractor in the world.

Conclusion With several lengthy work stoppages due to flooding of the access causeway, the piling is expected to be completed in mid- July 2017. Following on, the main contractor will complete the abutments and bridge piers and place the precast beams supporting the new deck providing a safe, dual lane link between the north and south banks of the Tugela River and helping to uplift Tugela Ferry and the entire surrounding area. 

Another disadvantage has been that when forming the socket with the cluster drill, the rock in which the socket is created is reduced to small chips and dust. This means that the rock quality is more difficult to assess post-drilling and a thorough geotechnical investigation is essential prior to construction. “As with most geotechnical works, the cost of a thorough geotechnical investigation is easily recovered during construction through design and construction cost savings, for the ultimate clien,” Pearce says.

90 tons and is ideally suited for the Tugela Ferry piling solution. “We owe a lot to the BG28 which has enabled Franki to implement many cost- efficient solutions to a wide range of clients since it first arrived in this country from Germany in 2012,” Pearce says. Another time-saving solution used by Franki was the construction of a movable ramp to create the required 1 in 6 rake, meaning that it is not necessary to modify the platform earthworks for each pile. “With all six pier piles raking in different directions this represents a major cost and time saving solution,” Pearce says. Dealing with the unexpected The necessary raised platform and variable rock levels, resulted in suitable founding rock only being encountered at depths of over 25 m for some piles – 10 m deeper than the average expected – but piling production has still met expectations. “The BG28 has comfortably dealt with deep boulder layers and, as expected, the cluster drill has formed sockets in vastly reduced time,” Pearce says. It was not all plain sailing, however, and one operational disadvantage has been that the hard boulders and rock have caused extreme wear on cutting teeth and bits, which have required regular maintenance and replacement.

Piling for the bridge piers on the new Tugela Ferry River Bridge.

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CONSTRUCTION WORLD JULY 2017