China has become the second nation in the world to master double-tube drilling technology while excavating a 2,668-meter-long tunnel for a Metro project in Shanghai.

Japan is the world's leader in the drilling process, known as the shield-excavation method, which can dig two tracks of a tunnel at the same time.

In traditional subway excavations, only enough space for a single track can be drilled out -- just a little more than 6 meters in width.

It is the first time Shanghai or China has adopted this double-tube technology. The tunnel being constructed is part of a metro line, M8, that goes from Yangpu District to Pudong via the Huangpu River.

Started less than one month ago, the tunnel has already been advanced 80 meters ahead. Engineers have been making steady progress, moving forward by 5-6 meters daily.

"Everything is going smoothly," said Tsutomu Tomisawa, an expert with the Daiho Corporation. Daiho is the Japanese company serving as technical partner for Shanghai Tunnel Engineering Co Ltd (STEC), which is constructing the tunnel.

"The double-tube shield, seemingly like connected twins, enjoys very promising prospects in Shanghai because even the underground space is increasingly limited," said Zhu Wenchan, STEC spokesman.

Since the two tubes of the tunnel can be completed at the same time, the new technology significantly saves time, Zhu said.

(China Daily September 10, 2003)