Multi-Purpose

CHINA’S
POWER LINE

It is a project of superlatives: a tunnel borer 12.07 meters in diameter cuts its way down to a depth of 74.83 meters beneath the Yangtze River with ground conditions characterized by high water permeability, high compactness and high quartz content. Maximum external pressure: 9.8 bar. And as if that were not enough: Methane deposits. “We have built plenty of tunnels before, but this one sets new standards in many respects,” says Chen Peng, Project Manager at China Railway 14th Bureau Group Co., Ltd. So it was all the more important that everything went right from the very first day: in only seven and a half months the experts from Herrenknecht and the 14th Bureau Group Co., Ltd. designed and built a machine that could meet the complex specifications of this contract.

THE TBM WAS DESIGNED AND BUILT IN RECORD TIME, THANKS TO PERFECT TEAMWORK BETWEEN HERRENKNECHT AND OUR PEOPLE.”

Chen Peng, Project Manager, China Railway 14th Bureau Group Co., Ltd

After the machine was transported from the Herrenknecht subsidiary in Nansha, Guangzhou to the launch shaft it only took another 45 days until it was fully assembled. “That was only possible because we and Herrenknecht worked together perfectly as a team.” On July 15, 2017 the tunnel boring machine began its almost 5.5 kilometer long mission under Asia’s largest river.

The Sutong GIL Cable Tunnel is part of the Huainan-Nanjing-Shanghai UHV AC project, which is designed to further increase the share of renewables in China. The problem: large amounts of green power are generated in huge hydropower plants in the mountainous west of the country. The electricity, however, is needed primarily in the metropolitan areas on the east coast. The solution: gas insulated transmission lines (GIL), i.e. tubes filled with sulfur hexafluoride in which a voltage of 1,000 kilovolts can be transmitted with minimum transmission losses. That is more voltage than any other line in the world can transmit. “We are building this tunnel primarily for the GIL network,” says Chen Peng. “But it also has room for additional lines.” The tunnel integrates six GIL cable lines at the upper layer. At the lower layer, there are two 500 kilovolts cable lines at the side as well as a service way in the middle. “As a 'multipurpose tunnel' it will ultimately fulfill multiple functions.”

Assembly in the launch shaft: a TBM with a diameter of 12.07 meters bores the multipurpose tunnel under the Yangtse.

  • Project: Sutong GIL Cable Tunnel; Changshu (China)
  • Client: State Grid Corporation of China
  • Contractor: China Railway 14th Bureau Group Co., Ltd.
  • TBM diameter: 12,070 mm
  • Tunnel length: 5,468.5 m