Creating a construction pioneer! Super shield of Beiheng Tunnel passed through Line 11 in operation.!

2019-02-19

A few days ago, with the support of Shanghai Shentong Metro Group Company, the new project section II of Beiheng Tunnel which is invested by Shanghai Chengtou Group Corporation and built by Shanghai Tunnel Engineering Company, completed the crossing of rail transit Line 11 in operation. This means that engineering construction of Beiheng Tunnel has overcome difficulties, and the team of Shanghai Tunnel Engineering Company since establishment has firstly completed construction of the shield for super large diameter of 15m which is crossing the rail transit in operation at close range.
The “Zongheng” Shield has a diameter of 15.56m and a height of 6-floor building. The shield, situated in the intersection between Changning Road and North Jiangsu Road, is crossing rail transit Line 11 “Longde Road Station~ Jiangsu Road Station”. Minimum vertical clearance from Line 11 Tunnel is about 7.06m, and the cutterhead area and tunnel crossing area are 1.8 times of previous project cases, so the risk is quite high.

At the same time, the passenger flow of Line 11 is too large to be suspended, and safe operation must be guaranteed during the construction period. After the comparison and selection of a variety of schemes, the scheme of “limiting the train speed and making the shield cross at constant speed” was determined. On the one hand, it brings many difficulties for control of vibration and sedimentation, and keeping stability of the excavation face. On the other hand, the “Zongheng” Shield makes a sharp turn with a radius of 500 meters during the undercrossing process, and the “perfect arc” makes the undercrossing task extremely difficult. It is the first time in the history of Chinese and foreign shield tunneling that the crossing is of extremely high difficulty.
Before and after shield crossing, municipal government, municipal Beiheng Tunnel headquarters, municipal transport administration commission, Shanghai Shentong Metro Group, Shanghai Chengtou Group and leaders of owner unit pay high attention to the project and give guidance to the work on the site for many times. Zhang yan, Party Secretary and Chairman of STEC, Zhou Wenbo, Deputy Party Secretary and President, Yang Lei, vice president, and other leaders of STEC provide the whole-process guidance and promotion and ensure safe and efficient engineering.

Fully guaranteed construction scheme and expert team
The construction team of Shanghai Tunnel Engineering Company carried out investigation and analysis for the crossing case with same type, conducted evaluation for tunneling data at pre-construction of “Zongheng” Shield, and formulated the crossing plan after simulating various scenarios. Communicated with Shanghai Shentong Metro Company actively to limit the speed of trains during formal crossing of the shield, so as to reduce vibration effect; meanwhile, prepared detailed planning for emergency, maintenance, emergency personnel evacuation, and subway tunnel rescue. In the control center of on-site shield, all parameters of “Zongheng” Shield and ground settlement monitoring data in the crossing area are shown on the monitor screen. Top shield experts gather in front of the screen all day long and prepare for “group consultation” at random.

All the preparation and guarantee work have been ready. At 10:00 am on November 16, under the deployment and guidance of municipal Beiheng Tunnel headquarters and municipal transport administration commission, the cutter head of “Zongheng” shield has put right below of Line 11 tunnel, and started the “ultimate trip”.

Correct and safe crossing
The shield cutterhead experienced 22 rings from entering the projective plane of Line 11 to leaving the projective plane, and the whole length is 44m. The “Zongheng” shield completed 7 rings every day, and construction units were on 24-hour duty. After 70-hour construction, at 9:00 am on November 19, the shield completed left the projective plane of the tunnel, which means that the shield has completed crossing of Line 11. Through monitoring, Line 11 tunnel deformation is controlled in the prescribed limit and the subway operation is uninfluenced.

The “encyclopaedia” of shield crossing
This is another difficult construction for “Zongheng” shield after the crossing of Zhaofeng villa group - protective historical building in Shanghai. During west-section construction of overall Beiheng Tunnel, the main shield will pass through 3 districts and 6 streets, over 100 various buildings, 3 transit stations (two stations are under operation, and one station is under construction), and various urban lifelines; in the future, 5 rail transit tunnels will be traversed in the eastern section.

Due to various risks such as sharp curve turning, shallow overburden and worse stratum, this crossing is of high comprehensive difficulty, complicated technology and accumulated risk, which is known as "the encyclopedia of shield crossing". The successful crossing of the rail transit Line 11 provides reference for safe promotion of Beiheng Tunnel shield.