(August 31, 1999) Two rows of ‘bubble curtains,’ resembling car air-bags, will be set in an effort to protect the main dam wall by absorbing 50 to 70 per cent of the energy from the huge blast that will demolish the top of the cofferdam Tuesday afternoon, Xinhua reports.

Measures have been taken to keep the just-completed main wall of the Three Gorges Dam, the world’s largest, safe and sound against the demolition of the project’s last cofferdam, which is due for Tuesday afternoon. Yu Ying, a technical expert with the Gezhouba Dam Group that is accountable for the demolition effort, said the main dam can stand the shock the blast would produce. The demolition will be operated by segments and will make fragments of the cofferdam tumble upstream like building bricks, according to Yu. Two arrays of “bubble curtains”, resembling air-filled bags for the protection of drivers and passengers in car accidents, will be set to absorb tremendous shock waves and surge pressure from the blast, in a bid to reduce their energy by 50 to 70 percent before they arrive at the main dam, Yu explained. The cofferdam, with its southern connection section joining the main dam, is measured 580 meters long, 140 meters in maximum height and eight meters in top width. The upper 30 meters of it, involving nearly 180,000 cubic meters of concrete, will be removed by using 192 tons of dynamite, with the under-water part of 110 meters in height to be retained as a protective structure for the main dam. After the demolition, the main dam will formally begin holding water and contribute to flood control.

Xinhua, August 31, 1999