Yangtze underwater rail tunnel reaches milestone

The world's largest shield machine for railway construction reached the halfway point of its underwater journey beneath the Yangtze River on Wednesday, marking a major milestone for the high-speed rail tunnel linking Shanghai's Chongming Island with Taicang, Jiangsu province.

Developed in China, the 148-meter-long machine — with a diameter of 15.4 meters — is edging closer to the most technically challenging section of the tunnel, according to China Railway Tunnel Group Co, the project's contractor.

"With a gradual downward slope, the pressure from the surrounding water on the construction project is rising," said Wang Yi, the project's deputy equipment manager.