A tunnel running under China's longest river, the Yangtze, in Jiangsu Province opened on Friday, a 5,853-meter-long engineering feat that will ease traffic congestion.

Eighty Chinese and foreign experts together with construction workers took more than four years to build the 4.12 billion yuan (US$603 million) six-lane project which includes a 3,790-meter-long tunnel.

The project encountered many difficulties in the underwater geological environment, and various technical problems had to be overcome.

"An area as big as a nail has to bear about 6.5 kg of pressure at a depth of 65 meters. That is a lot of pressure for a tunnel to bear," said the project's chief engineer Han Xiangyang.

The designers performed many world-class technological feats during the project, he added.

The tunnel is able to handle double the traffic-flow the Nanjing Yangtze River Bridge, a trunk road spanning the river, currently does.

It is the third traffic tunnel built under the Yangtze River coming after one in Wuhan, capital of central China's Hubei Province, and another in Shanghai.

(Xinhua News Agency May 29, 2010)