The first steel boxed cofferdam for the west cable tower of Lingdingyang Bridge of Shenzhen-Zhongshan Bridge was successfully placed on November 6. [Photo provided to Zhongshan Daily] 

Based on sources from the Management Center of Shenzhen-Zhongshan Bridge, the installation of the steel boxed cofferdam marked the official start of the construction of the main pier cap of the west cable tower of Lingdingyang Bridge.

The Lingdingyang Bridge is a three-span floating suspension bridge with a main hole span of 1,666 meters and a height of 91 meters from the deck to the water surface, which is equivalent to a height of 30 floors. 

The west cable tower is the key project of the whole bridge, which is undertaken by Poly Changda Engineering Co Ltd. The west cable tower is a separate cap, which comprises of two cylinders with a diameter of 36 meters and a height of 8 meters. The double-walled bottomed steel boxed cofferdam serves as the water retaining and formwork structure for the cap construction. 

"After the steel boxed cofferdam is lowered to the water, it would be like placing a giant box in the sea. The bottom of the steel boxed cofferdam is connected to the pile foundation and fixed together to isolate the seawater. After the bottom of the steel boxed cofferdam is sealed and the seawater in the box is drained, a small 'artificial island' can be formed in the sea for the next step of the cap construction." Zhang Yutao, deputy production manager, gave a detailed introduction. "As a permanent anti-collision facility of the bridge, the steel boxed coferdam can minimize the damage to the pier caused by ships, and provide a good safety guarantee for the bridge. In addition, it can also effectively prevent seawater from corroding the cap," he added. 

It has been reported that the steel boxed cofferdam is 17.6 meters in height, 2.5 meters in thickness and 41.1 meters in outer diameter. It is a 6-storey, 1,800-ton "iron giant" that is as large as two basketball courts.