Overcoming the gigantic 113-meter height difference created by the Three Gorges Dam on the Yangtze River used to require navigating a complex system of five stepped locks, a journey that delayed ships between three and four hours. To streamline naval traffic, engineers designed an unprecedented machine: the Three Gorges boat lift, the largest and heaviest vertical lifting structure on the planet.
The heart of this engineering work is a watertight concrete and steel chamber 120 meters long, 18 meters wide, and with a 3.5-meter draft. When filled with water to accommodate a vessel of up to 3,000 tons displacement, the total suspended weight reaches an enormous 15,500 tons, the equivalent of two and a half times the mass of the Eiffel Tower.
To lift such a massive load without astronomical energy consumption, engineering relied on an elementary physical principle pushed to the extreme: counterweights. The weight of the chamber is precisely offset by four groups of concrete blocks suspended by 256 high-strength steel cables.
The biggest challenge was not hoisting the mass, but preventing the chamber from swaying or becoming misaligned. Even a millimeter of tilt would cause the water inside to shift violently, unbalancing the structure. To solve this, four gigantic pinion and gear rack mechanisms guide the ascent along four 169-meter-high concrete towers, ensuring that the basin remains perfectly horizontal, immune to wind and seismic shocks.
Source: China Three Gorges Corporation / International Commission on Large Dams (ICOLD)
