Five-Step Ship Locks


China Yangtze Three Gorges Project, as one of the biggest hydropower-complex project in the world, ranks as the
key project for improvement and development of Yangtze River. The dam is located in the areas of Xiling gorge, one
of the three gorges of the river, which will control a drainage area of 1 million km2 , with an average annual runoff of
451 billion m3. The open valley at the dam site, with hard and complete granite as the bedrock, has provided the
favorable topographical and geological conditions for dam construction.

The following indices are the biggest in the world: total water head of 113 m, inland river ship lock of five stages, a
lock chamber's effective dimension of 280 m×34 m×5 m (length × width × minimum water depth on the sill), inland
river ship lock with capacity to accommodate 10000-tonnage fleets, maximum operating water head 49.5 m for a
gate of its water exchange system, maximum water fill/discharge amount of 260000 m3, maximum side slope
excavation of 170 m, in height and etc. The operating water head exceeds the world record.

Double-way and five-step ship lock was excavated through the ridge to the left of the hydropower complex, with
upstream and downstream approach channels connecting to the Yangtze main channel. The total length is 6442 m including 1607 m for main
body section. Continuous high slopes lie on both sides of the ship lock, with maximum height of 170 m, the area of more-than-120 m-high slope
extends for about 460 m long.

Considering the characteristics and the importance of the side slope, the engineers took the following measures: drainage from inside the ridge,
elimination of ground water, installation of pre-stressed steel-cords and high-strength steel anchors.

During the construction, the engineers strictly followed construction procedure, applied a whole set of
controlled blasting, strengthened prototype monitoring and feedback analysis, and carried out dynamic
analysis. According to synthesis and analysis on the data collected from 3,268 monitoring devices
embedded in every corner of the ship lock, the rock deformation became stable after excavation
completed in April 1999. When the ship lock was put into operation, the shift in ship lock chamber is
less than 0.5 mm during filling the lock chamber, fully meeting the normal operation requirement of
miter gates.