The world's widest tunnel with an inner diameter of 13.7 meters completed its excavation in Shanghai under the Yangtze River on Friday.

A minivan runs through the Yangtze River Tunnel in Shanghai, September 5, 2008. The world's widest tunnel with an inner diameter of 13.7 meters completed its excavation in Shanghai under the Yangtze River on Friday. The 8.9-km tunnel is part of a 12.6 billion yuan (US$1.84 billion) bridge and tunnel project to link Shanghai with Chongming Island, the country's third largest after Taiwan and Hainan.(Xinhua Photo)

The 8.9-km tunnel is part of a 12.6 billion yuan (US$1.84 billion) bridge and tunnel project to link Shanghai with Chongming Island, the country's third largest after Taiwan and Hainan.

The tunnel will accommodate a six-lane expressway and a rail line. When operational in 2010, travel to Chongming from urban Shanghai will take 20 minutes, according to Yu Xuanping, vice general manager of the Shanghai Tunnel Engineering Co., Ltd, builder of the tunnel.

The company used a tunnel boring machine with a diameter of 15.43 meters, the largest of its kind, to excavate under the Yangtze.

The tunnel and bridge project would make the transport networkson the southern and northern sides of the river more closely connected, said Wu Liangyong, a Chinese Academy of Sciences academician.

The tunnel connects Shanghai's vast Pudong District with Changxing Island in the Yangtze, while the bridge connects Changxing and Chongming.

Currently, Chongming is connected with Jiangsu Province to its north.

Located at the Yangtze River mouth, Chongming covers an area of1,200 sq. km, equal to about 20 percent of Shanghai's total land area.

China's central government plans to turn the island into a model of an eco-friendly town in the country. Shanghai municipal government is also paying great attention, with infrastructure projects being built within the island.

Experts said the inconvenient traffic between Shanghai and Chongming once blocked the development of the island. The construction of the bridge and tunnel would help attract overseas investment and make the suburb a major channel of the Yangtze River Delta area.