World's First Large-Diameter Shield Tunnel to Work Beneath an Operating High-Speed Railway Starts Excavation

The Tongjing Road Tunnel in Suzhou, East China's Jiangsu province, is being excavated by the world's first large-diameter shield tunnel to work beneath an operating high-speed railway. The excavation started on Oct 26.

Designed by China Railway Fifth Survey and Design Institute Group Co., Ltd. and contracted by China Railway 14th Bureau Group Co., Ltd., both subsidiaries of China Railway Construction Corporation Limited (CRCC), the tunnel construction is a typical solution of CRCC in urban development integrating design, engineering and equipment manufacturing.

Located in Huqiu district, Tongjing Road was separated into two disconnected parts by the Shanghai-Nanjing Intercity Railway.

The separation restricted development of the Huqiu Mountain Scenic Spot and Shantang Street – a historical and cultural protection zone.

With a designed speed of 60 kilometers per hour, the double-holed six-lane tunnel will be 490 meters long and feature two layers, the carriageway on the top and the escape route and pipeline passage at the bottom.

In addition to the busy railways and subways, the tunnel will also pass under some popular tourism spots like the Wanshunlou Hotel and the Bao'en Temple, which adds difficulty to the engineering.

Some innovative technologies and systems were developed for the project, including a visual smart engineering system that can realize real-time control of the shielding parameters and a smart monitoring and alerting system that collects sediment data around the structures. The low clearance full casing piling machine and its related technologies as well as the intelligent accurate penetrating control technology of large-scale slurry shielding are being used in such projects for the first time in China.

The 13.67-meter diameter slurry balanced tunnel boring machine used in the construction was jointly developed by China Railway Construction Heavy Industry Corporation Limited and China Railway 14th Bureau Group Co., Ltd.

Limiting any environmental impact is also highly valued during construction. The modular mud treatment system releases zero pollutants and the project's treated water can be directly discharged to the urban rainwater drainage pipe or used in slurrying.

According to Wang Xiaoqiong, head of the project, the underground tunnel will expand the Tongjing Road to the north to link the two separated parts.

The 2,490-meter expansion project is a main support for the seven main north-to-south arteries in Suzhou and a key passage to be constructed during the 13th Five-Year Plan (2016-20).

It is expected to open to traffic in 2022 and will improve the traffic condition of the city.

The tunnel boring machine starts operation at the Tongjing Road Tunnel project in Suzhou on Oct 26. [Photo/sasac.gov.cn]

A map of the risk points the Tongjing Road Tunnel will go under [Photo/sasac.gov.cn]

Managers of the project inspect the tunnel boring machine before its operation. [Photo/sasac.gov.cn]

(Executive editor: Wang Ruoting)