At 4:30 pm on January 15, amid the rumbling excavation of a shield tunneling machine, the first underground rail transit cross passage constructed using the shield tunneling method broke through on the section from Yinzhou District Government Station to South Business District Station of Ningbo Rail Transit Line 3. The cross passage has a diameter of 3.15 meters and a length of 17 meters. It is understood that this is the world's first underground cross passage constructed using the shield tunneling method.
A cross passage is an escape passage in the middle of a tunnel, generally used for the evacuation of firefighters and passengers in emergencies. In rail transit construction, a cross passage is required every 600 meters of tunnel. The better method in China is manual excavation using the freezing method, while the more popular international method is mechanical pipe jacking. Manual excavation is inefficient, and the jacking distance of the pipe jacking method is limited, so this has long been a major technical pain point in cross passage construction at home and abroad. Ningbo Rail Transit Group used its independently developed third-generation quasi-rectangular shield tunneling machine to complete the excavation of the cross passage using the shield tunneling method. The excavation distance is long, and equipment attitude adjustment is easy, making up for the shortcomings of manual excavation and mechanical pipe jacking operations, and offering advantages such as safety, high quality, high efficiency, and environmental protection.
According to reports, if the conventional manual excavation method were used, this short 17-meter tunnel would take three to four months, while the shield tunneling method took only 18 days.
From launch to success, the project team led by Ningbo Rail Transit spent more than a year on the shield tunneling method project. The project applied for more than 10 national invention patents and overcame nearly 10 major technical challenges, including built-in pump room technology within shield tunnel sections, research and development of integrated shield tunneling equipment sets, and segment structure cutting. A complete set of shield tunneling equipment for cross passages was successfully developed, and a construction process plan meeting the requirements of rail transit shield tunnels was formed. On December 9 last year, the shield tunneling method project successfully passed review.
Sun Jun, an academician of the Chinese Academy of Sciences, said that the success of this project will open up a new construction method for underground cross passages internationally and has very broad application prospects.
According to relevant data from the China Association of Metros, the mileage of underground rail transit lines to be built nationwide last year was about 5,000 kilometers, including several thousand such cross passages. Shield tunneling cross passage technology can be applied not only to cross passages of urban rail shield tunnels, but also widely in municipal utility tunnel branch shafts and maintenance shafts, deep tunnel connection lines, and underground space connection projects, and has extremely high promotion value. At the same time, this technology has taken an important and solid step toward non-excavation and full mechanization in urban underground engineering.