Construction of Largest, Heaviest Immersed Tube of HKZM Bridge Revealed in Detail
The undersea tunnel of the Hong Kong-Zhuhai-Macao (HKZM) Bridge is composed of segments of giant immersed tubes. Currently the tube is the largest and heaviest building unit for an underwater tunnel in the world, so how was such a jumbo constructed? To ensure its service life originally designed to last for 120 years, it has been prefabricated in a manageable length in modular structures since 2012. The modular prefabrication design makes its debut in China and is only the second case across the world. Each standard immersed tube is 180 meters long, 37.95 meters wide and 11.4 meters high, and is made of steel bars and reinforced concrete. It uses more steel than the Eiffel Tower did. With cast concrete, its weight exceeds 80,000 tons, equivalent to a colossal aircraft carrier. With its primitive form being a reinforcement cage made up of numerous steel bars, the tube is composed of eight segments with more than 400,000 steel bars in aggregation. How to keep these bars in normal shape under an overwhelming weight is an intractable problem. "The reinforcement cage used to be flexible. So we need to add some light-weight frames to it, which will then form a framework after being connected," said Zhang Hong, engineer with the Island and Tunnel Project of HKZM Bridge Joint Venture of China Communications Construction Co., Ltd.. If the framework of the immersed tube takes shape from colligation of the reinforcement cage, then its flesh is the cast concrete. During this process, ice cubes are used to keep the temperature of the concrete at around 25 degrees Celsius. Meanwhile, more than 100 workers need to start the job simultaneously. "Around 100 workers must keep casting concrete in the framework for more than 30 hours without intervals. No accident is allowed because once it happens, delamination, another expression of cracks, will occur in the concrete, making it prone to seawater erosion or leakage that will affect the life span of the immersed tube," said Chen Weibin, another engineer with the grand project. It takes approximately two months to produce an immersed tube which will then be equipped with a range of sealing parts. It will be towed to the final location with the help of buoyancy and aligned correctly with other tubes to form the undersea tunnel. More on:http://www.cctvplus.com/news/20161005... Subscribe us on Youtube: / cctvplus CCTV+ official website: http://www.cctvplus.com/ LinkedIn: / cctv-news-content Facebook: / newscontent.cctvplus Twitter: / cctv_plus
