On December 8, 2011, the massive eight-hammer vibratory pile driver hammer dubbed the "Octakong" drove the last of 120, 72-ft.-diameter steel piles into place in front of a crowd of over 200 people who came to witness the world's largest pile drive to grade. The final record breaking pile completed construction of two circular seabound walls in the South China Sea for the Hong Kong-Zhuhai-Macau Seaway project.
The enclosed sea-bound walls are to form bulkheads for two artificial islands under construction for the Hong Kong-Zhuhai-Macau Seaway project due to be finished 2016. The two islands will form transition structures between the project’s 4.2-mile tunnel section, built to allow deep water ship access to the Pearl River Delta from the South China Sea, and three cable-stayed bridge spans linking Hong Kong in the east to Macau and the mainland Chinese city of Zhuhai to the west.
An Experiment in Innovation
The artificial islands’ seawalls comprise 60 individual adjoining cells, each adjoined by wingwalls, in order to form to perimeter of the island. Traditional construction methods of the bulkheads would have taken years. Each cell would have to be fabricated individually by driving one interlocking sheet pile at a time to form each cell, and each cell constructed to adjoin the next until the island wall perimeter was closed.
A construction method driving the cells as individual massive steel piles had never been tried on this scale in these conditions. The pile driving equipment capable to supply the force to drive the piles had been conceived but not yet constructed.
Allnamics Pile Testing Experts of the Netherlands helped convince Chinese contractor First Harbor Marine Group China that a massive multi-vibro hammer could be used to drive the 130-ft.-long, 72-ft.-diameter steel pipe piles, weighing 600 metric tons each, into the sea bed to the required depth.
The Octakong hammer was made in the U.S. by American Piledriving Equipment, Inc. (APE), Kent, WA, and shipped to China, where it was assembled and put to work. Specially designed, engineered and manufactured for the project, the Octakong consists of eight synchronized vibratory pile drivers powered by eight 1,200-hp CAT engines. By using the innovative pile driver to drive the piles, the construction schedule was reduced to less than 7 months.
Commenting on the project, John White, APE President, said, “The completion of the circumference of each island’s wall marks major advancements in the field of sea-bound construction, land reclamation technology and pile driving – at 72 ft. these are the largest diameter steel piles ever installed.”