Installation of all 33 undersea tunnel immersed tubes of the Hong Kong-Zhuhai-Macao Bridge complex was completed on Dec 26 after the last cubic meter of concrete was cast at the prefabrication factory on Niutou Island. 

A single standard immersed tube is 180 m long and weighs 80,000 tons, equivalent to a mid-sized aircraft carrier. Over a period of six years, China Communications Construction Co Ltd (CCCC) constructed 33 of them to create a watertight feat at more than 40 m under the sea with zero cracks in one million cubic meters of concrete. This resulted in a solid foundation for the 120-year lifespan of the bridge’s undersea tunnel.   

Niutou Island Immersed Tube Prefabrication Factory [Photo courtesy Zhuhai Daily]

As the world’s largest modern immersed tube prefabrication factory, the Niutou Island plant was established in February 2012. The 560,000 sq m super factory took only 14 months to build on the deserted island with no water or electricity. It has two flow production lines with a length of more than 300 m, integrating reinforcement steel processing and cage colligation, concrete casting, pipeline junction one-time fitting-out, impounding and drainage, and pipeline junction floating and traversing. Without any malfunction in equipment, the factory is also the first in the world to have realized 200 m-incremental launchings for the huge immersed tubes. 

As the dominant engineering of the HZM Bridge, the island-tunnel project includes eastern and western created islands, the undersea tunnel, and non-navigable bridges. The 6.7 km tunnel is the world’s longest immersed roadway and the only deeply buried one. It is also China’s first open sea immersed tunnel. The tubes were all produced in assembly line under the Factory Act. They were towed by more than 10 large tugs to areas 13 km away from the factory and installed in undersea foundation trenches within centimeter-level errors. 

A milestone in the development of Chinese bridge construction, the Hong Kong-Zhuhai-Macao Bridge was honored as the Mount Everest of bridges and regarded as one of the “Seven Wonders of the Modern World” by The Guardian newspaper in the UK. It is scheduled for final completion and opening in 2018. At a combined length of approximately 35.6 km, it is the world's longest sea bridge. Travel time by roadway between Hong Kong and Zhuhai or Macao will be reduced to 40 minutes from the current 4.5 hours.