Plain sailing with Franki …
The Yacht Club: a testament to Franki’s Foreshore experience
Due to the past successful working partnerships between Franki and AMDEC, Franki was the preferred contractor for this challenging geotechnical work
AMDEC Property Development’s (AMDEC) The Yacht Club development is a picturesque, nautically inspired design, located on the Cape Town Foreshore in the Roggebaai Canal Tourism Precinct near to the Cape Town International Convention Centre (CTICC) and directly south of the new multi million Rand cruise liner terminal.
The Yacht Club, a multi-use development including commercial and residential space, is destined to become one of Cape Town’s most sought after destinations and is yet another prestigious AMDEC/Franki Africa partnership.
The site is situated on the Malmesbury group deposition of the Cape Peninsula, Cape Supergroup in the Foreshore area of the harbour reclamation development of the 1920’s and 1940’s. The shale bedrock is overlain by very stiff residual material followed by marine deposits and fill comprising of old harbour facilities, general tipped rubble and dredged sands.
The ground water table was intersected at an average depth of 0.86 m with the bedrock falling from around -0.84 m in the west to -2.9 m in the east (elevation levels in ASML).
Special attention was required to an existing sub-surface canal running south to north which intersects the eastern portion of the site with both the lateral support and piled foundation design modified to accommodate and maintain the integrity of this structure.
Some of the existing live services which required special attention to maintain supply to neighbours
“It is evident that from a geotechnical perspective the Cape Town Foreshore is not the easiest area in which to operate. The varying ground conditions with old rock-filled docks and piers and the high water table described above present a significant challenge,” says Franki’s Rod Schultz. “But our previous experience on the neighbouring Harbour Bridge and Canal Quays projects has given us a thorough understanding of the prevailing ground conditions in the area and enabled us to quickly offer our client the most cost-effective solution,” he says.
Schultz continued saying that it took some years of on-and-off development proposals by all concerned before AMDEC succeeded in producing a workable solution by securing the land and obtaining the necessary partnerships to go ahead.
Site overview showing the phased construction sequence and restricted access.
Due to the past successful working partnerships between Franki and AMDEC, Franki was the preferred contractor for this challenging geotechnical work. “We know Franki’s exceptional capabilities in the Foreshore area, which requires a special understanding of its complex geological conditions. We had no hesitation in awarding Franki this contract and their performance certainly lived up to expectations,” says AMDEC’s Project Manager Arnon van As.
Franki’s scope of works included the design and installation of the lateral support and foundation piling to this multi-storeyed, double-basement project, the excavation and disposal of some 65 000 mᶟ of bulk earthworks, 508 lm of lateral support and 271 no. foundation piles.
The soldier piles for the lateral support were a combination of 400 mmØ Continuous Flight Auger (CFA) piles and 325 mmØ Rotapiles tied back with a single row of anchors and gunite arches. The anchors had to be carefully positioned and inclined sufficiently to not intersect with the canal, which runs very close to the site.
Piling and bulk earthworks operations at peak with upwards of 5 piling rigs, 2 excavators and more than 200 tipper truck loads per day
CFA piling is a fast and economical system with no vibration and limited noise levels associated with it. “This was particularly advantageous on a site which is close to live canals and railway lines, contains a labyrinth of existing services and has neighbours who are particularly sensitive to noise,” says Schultz.
The main feature of the Rotapile system is its ability to penetrate boulders and rock formations. Socketing into hard rock is effected rapidly using the ‘Down The Hole Hammer’ (DTH) percussion drilling technique. As with CFA, noise levels are low and vibration limited.
Schultz says that the foundation piles were designed with flexibility in mind to meet the varying and sometimes unpredictable ground conditions. Three pile types were used: the Franki Driven Cast-in-Situ piles, Temporary Cased Augers and Oscillator piles with individual load bearing capacities from 2 300 kN to 10 000 kN.
To say that the Franki Pile is the most well known piling system in southern Africa is certainly no exaggeration. Developed circa 70 years ago it is still one of the most popular pile types in this region. Its main feature is the large base formed at the toe of the pile and, in forming it, the end-bearing area is considerably increased. It is generally a very economical system, has an extensive range of pile sizes and, like the other piling systems used on The Yacht Club site, its noise levels are relatively low.
Another significant challenge on this project was the very demanding schedule. “This meant that the works not only had to be very carefully planned but also executed to perfection,” says Schultz.
He explains that AMDEC required a phased handover to the main building contractor so that the critical-path tower cores and basement sections could be started whilst Franki were still busy on site. “We started operations during the latter half of 2016 and completed everything on time and within budget by mid-March 2017,” he says.
Schultz paid tribute to Franki’s client, AMDEC, and to bulk earthworks contractor, Ross Demolition. “To have successfully completed this project on time we needed it to run like clockwork. This was facilitated by these two professional companies which pulled out all the stops to ensure that we could do it,” Schultz concluded.