On October 10, construction officially began on the upstream and downstream cofferdams for the Gezhouba navigation capacity expansion project, a key component of the Three Gorges new waterway project, marking the expansion project’s full entry into the main construction phase.
Together with the riverbank slopes, the two cofferdams will enclose the work area, creating the preconditions for dry-land construction of the new 10,000-ton ship locks.
An aerial photo of the Gezhouba hub. [Photo/sasac.gov.cn]
The navigation capacity expansion project, on the left bank of the Gezhouba hub, will remove the existing No 3 ship lock and build two new 10,000-ton locks on its original site, each measuring 280 meters in length, 40 meters in width and 8 meters in height. Upon completion, single 10,000-ton vessels will be able to navigate smoothly through the Gezhouba hub.
The cofferdams are the first critical engineering step for the Gezhouba navigation capacity expansion project. A cofferdam is a water-retaining structure in the river that can cordon off the lock construction site from surrounding waters. Once the foundation pit is drained, construction crews can demolish the old lock and excavate and lay concrete for the new locks, just as they would do on dry land.
The upstream cofferdam is a Grade I temporary hydraulic structure, with flood control standards in compliance with those of the Gezhouba main dam. The 835.94-meter-long and up to 28-meter-high structure is expected to be completed within 24 months. Its construction involves a dredging volume of around 518,000 cubic meters and a filling volume of approximately 1,015,200 cubic meters. The downstream cofferdam has four segments -- respectively made of concrete, steel piles, earth-rock and gabion, with an overall length of 960.85 meters.
“The cofferdam construction zone lies within the core navigable waters of the Gezhouba hub. We must make the most of the low-water window to ensure timely closure of the cofferdams while coordinating navigation security and other related work,” said a senior official of the subsidiary of China Three Gorges Corporation, which is responsible for the Gezhouba expansion project.
He also said that the project team will strengthen whole-process safety and quality control and advance cofferdam construction to high standards, so as to lay a solid foundation for subsequent main construction of the ship locks.
(Executive editor: Zuo Shihan)
