Chinese engineers have completed the world’s first tunnel specialized for ultra-high-voltage power transmission lines, designed to cross the Yangtze River in East China’s Jiangsu province.
The tunnel is a key section of the 1,000-kilovolt UHV power transmission project linking Huainan, Nanjing and Shanghai, which aims to help ease power shortages in the Yangtze River Delta region.
The tunnel is 5,468.5 meters long and 12.07 meters in diameter, crossing the Yangtze River from Nantong in the north to Suzhou in the south. The lowest point of the tunnel is 74.83 meters below the water level of Yangtze River.
A specially designed 140-meter shield tunneling machine started excavation work on June 28. The machine was modified to adapt to high water pressure and complex geological conditions on the riverbed.
The machine excavated 14.12 meters per day, setting a new record compared to the average 11.6 meters of similar projects in China.
Experts investigated local conditions and realized building towers in the Yangtze River for overhead power lines would block shipping traffic in the river, and the foundations would need frequent maintenance.
All things considered, the tunnel was built so the power lines could be laid beneath the river, which has the advantages of lower construction and maintenance cost and avoids environmental destruction.
The transmission lines in the tunnel would be gas-insulated metal enclosed ones, bringing many benefits such as good transmission performance, outstanding safety, less space and lower maintenance cost compared to normal cable lines.
With an investment of 4.763 billion yuan ($696.8 million), the Suzhou-Nantong section is projected to be put into use in the next year.