From the Ground Up
Arup director Philip Lai explains the shaft-grouted barrette foundations of the International Commerce Centre.
Harbor View The ICC looms above the West Kowloon Station's levels of retail and mass transit. Views from within the shaft overlooking Victoria Harbor are expansive, especially from the Ritz-Carlton Hotel rooms at the top.
Photo courtesy Ritz-Carlton Hotel, Hong Kong
Tailored Tower The ICC’s elongated, glass-paneled shaft tapers gently toward the roof. Floors in the tower are typically 32,000 square feet, gradually shrinking to 29,000 square feet above the 78th floor. As the tower inclines inward 1 degree toward the top, the four glass facades seem to lift away from the shaft. In the crevasses, the reentrant corners gradually widen to mitigate wind turbulence, one of the major challenges for the supertall structure.
Photo courtesy Ritz-Carlton Hotel, Hong Kong
Tailored Tower The ICC’s elongated, glass-paneled shaft tapers gently toward the roof. Floors in the tower are typically 32,000 square feet, gradually shrinking to 29,000 square feet above the 78th floor. As the tower inclines inward 1 degree toward the top, the four glass facades seem to lift away from the shaft. In the crevasses, the reentrant corners gradually widen to mitigate wind turbulence, one of the major challenges for the supertall structure.
Photo © Grischa Rüschendorf
When the four facades reach the top, they form parapet walls at the roof level. At the base, angular glass-paneled canopies for offices and the hotel shelter visitors arriving by car on the top of the station roof.
Photo © Tim Griffith
On the north side, the glass forms a scooped canopy over the atrium connecting the tower to retail and mass transit below.
Photo © Grischa Rüschendorf
On the north side, the glass forms a scooped canopy over the atrium connecting the tower to retail and mass transit below.
Photo © Takuya Watanabe
Sleek Surround KPF designed the public lobbies and circulation spaces for the tower’s offices, using a corporate-posh palette. Cove lighting articulates the horizontal strips of travertine marble cladding the walls. The Ritz-Carlton Hotel has two lobbies, with the main one on the 103rd floor.
Photo © Tim Griffith
A smaller “street” lobby at “Level 9” is reached by driving up a curving road to the hotel entrance atop the station roof. The Singapore-based LTW Design Works designed the rectangular hotel lobby, which includes a pastry café, in a softly hued contemporary-luxe manner.
Photo © Chris Cypert
LTW Design Works (rooms, public spaces); Spin Design Studio (restaurants); Wonderwall (bar)
Image courtesy Ritz-Carlton
LTW Design Works (rooms, public spaces); Spin Design Studio (restaurants); Wonderwall (bar)
Image courtesy Ritz-Carlton
LTW Design Works (rooms, public spaces); Spin Design Studio (restaurants); Wonderwall (bar)
Image courtesy Ritz-Carlton
LTW Design Works (rooms, public spaces); Spin Design Studio (restaurants); Wonderwall (bar)
Image courtesy Ritz-Carlton
International Commerce Centre
LTW Design Works (rooms, public spaces); Spin Design Studio (restaurants); Wonderwall (bar)
Image courtesy Ritz-Carlton
International Commerce Centre
LTW Design Works (rooms, public spaces); Spin Design Studio (restaurants); Wonderwall (bar)
Image courtesy Ritz-Carlton
International Commerce Centre
LTW Design Works (rooms, public spaces); Spin Design Studio (restaurants); Wonderwall (bar)
Image courtesy Ritz-Carlton
International Commerce Centre
LTW Design Works (rooms, public spaces); Spin Design Studio (restaurants); Wonderwall (bar)
Image courtesy Ritz-Carlton
International Commerce Centre
Image courtesy Ritz-Carlton
International Commerce Centre
Image courtesy Ritz-Carlton
International Commerce Centre
Image courtesy Ritz-Carlton
International Commerce Centre
Image courtesy Ritz-Carlton
International Commerce Centre
Image courtesy Ritz-Carlton
International Commerce Centre
Image courtesy Kohn Pedersen Fox Architects
International Commerce Centre
Image courtesy Kohn Pedersen Fox Architects
International Commerce Centre
Image courtesy Kohn Pedersen Fox Architects
The tower is located above a cliff-like bedrock profile varying from about 70m to 130m in depth, which posed uncertainties in the use of traditional pile types. A tower of this height would require large concrete piles to support its enormous weight if the ground immediately under the building could not provide the required bearing capacity. For piles deeper than 90m below ground, there is increasing risk of collapse during excavation and also defective concreting.
In designing the foundations, we talked to good foundation contractors in Hong Kong to understand the difficulty imposed by technology of their equipment and thus the risks they would be taking. At the end we worked with a French contractor who was a specialist in construction diaphragm walls and barrette piles.
After elaborate studies being carried out, we decided to go for shaft-grouted barrette as the foundation system. The barrettes are rectangular reinforced concrete piles. To avoid construction risk at great depth as well as differential settlement, we adopted a friction mechanism for the piles to transfer the tower loads to the ground rather than a bearing mechanism. The piles transfer the loads through friction on their four sides to the adjacent soil instead of their bottom face as they would in the bearing mechanism.
The excavation for each pile employs the diaphragm wall method, which basically uses a machine to grab the soil out of the ground in a bentonite solution. The excavation is not carried down to the bedrock. Upon completion of excavation to the required depth, the pile is concreted while the bentonite solution is simultaneously pumped out to a collection tank. After the concrete sets, the concrete and soil interface of the barrette is injected with pressured grout. This grout creates an approximately 35mm cementitious layer between the barrette and adjacent soil, enhancing the friction between the barrette and adjacent soil and thus the load capacity of the barrette. The foundations consist of 241 barrettes with an average depth of 70m. Two sizes of barrettes are used – 2.8m x 1.0m and 2.8m x 1.5m.
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