Why did it take more than 8 years to cross the core area? The second east-west transportation artery main tunnel in Shanghai will be opened to traffic next year

With the slow entry of the 15 meter diameter super large shield tunnel "Jiangong Hao" today, the eastern section of the North Cross Passage tunnel is fully connected. "This means that the main tunnel of the new construction project of the North Cross Passage is officially connected, laying the foundation for its opening next year," said Huang Guobin, Chairman of Shanghai Urban Investment Highway Investment Group and Commander of the North Cross Passage Project Site Command.

Plan schematic diagram of the North Cross Passage project

The North Cross Passage, with a total length of about 19.1 kilometers, is known as the "second east-west transportation artery in Shanghai" and was once hailed as the "Shencheng No.1 Transportation Project" in the industry, demonstrating its importance. Since the start of construction in December 2014, the progress of the construction of the North Cross Passage has accompanied Shanghai citizens for more than 8 years. Why has it taken so long?

Produced by Qi Yingpu

30 years of preparation prior to commencement of construction

Compared to the construction period of the North Cross Passage, its planning has been brewing for a longer time.

Today, at the construction site located at the intersection of Zhoujiazui Road and Anguo Road, 10 meters underground, the reporter saw the excavation tool "Jiangong" with slowly rotating blades. In the preliminary plan, the terms "underground", "tunnel", and "shield tunneling" almost never appeared.

According to historical data, the North Cross Passage had already been reserved for planning as early as the 1980s. The earliest design concept was a full line elevated road, but there are still many differences from the final plan of some elevated roads and some tunnels today. The initial plan has not been implemented yet, mainly due to technical constraints. If underground construction was adopted, the engineering technology at that time could not yet achieve it; If the entire line is elevated, it will have a significant impact on surrounding residents and traffic.

For the next 30 years, the idea of building the North Cross Passage was temporarily put on hold, and urban development and technological progress brought possibilities for its implementation.

Plan diagram of the eastern section of the North Cross Passage project

In late June and early July 2013, the North Cross Passage was officially unveiled to the public. According to a 2013 report by the Liberation Daily, the special plan for the North Cross Passage, which runs through the six districts, was publicly announced on the official website of the Shanghai Planning and Land Resources Management Bureau. The announcement emphasizes that the North Cross Passage is a component of the "Three Horizontals and Three Verticals" backbone road network within the Inner Ring Road of Shanghai.

From a transportation perspective, a major function of the North Cross Passage is to solve the "urban disease" - congestion problems. The Tianmu Road interchange was particularly typical at that time, as it was a major obstacle to traffic congestion. Relevant parties had been seeking solutions to alleviate traffic congestion, but the results were minimal. In the long run, as the second east-west transportation artery, the North Cross Passage also needs to alleviate the problem of uneven regional development.

According to the 2013 Liberation Daily, due to factors such as geographical environment, railway channels, and long-term accumulation of unbalanced development, the development of Putuo, Hongkou, Yangpu, and the former Zhabei in the four areas north of Suzhou River is relatively lagging behind. The report mentioned that during the 12th Five Year Plan period, major urban infrastructure projects that need to be further promoted include the North Cross Passage.

Today, the truly established North Cross Passage starts from the middle ring road of Beihong Road in the west and ends at Neijiang Road in Zhoujiazui Road in the east, spanning six administrative regions in Shanghai: Changning, Putuo, Jing'an, Huangpu, Hongkou, and Yangpu, involving 17 streets, 2 towns, and 67 household committees. The underground tunnel section is about 14.7 kilometers long, with the western section being 7.8 kilometers long and the eastern section being 6.9 kilometers long. Its direction is based on the direction of Shanghai's economic development, constantly adjusting the linear direction, in order to better adapt to local conditions and assist in the economic development along the route.

The West East Line has not yet been officially connected

In June 2021, the western section of the North Cross Passage tunnel was officially opened to traffic. When can the eastern section of the tunnel be fully connected to the western section after it is completed today? Why does the construction period last for over 8 years?

Huang Guobin told reporters that in terms of the main structure, the western and eastern sections are already connected, and the construction team will continue to focus on promoting the construction of the internal structure of the tunnel. For example, ancillary projects such as mainline electromechanical, decoration, asphalt, and traffic safety facilities, as well as acceptance work for fire protection and transportation, will not be fully opened until next year.

"It is very difficult to promote such a large-scale underground project in the urban areas of super large cities," he said. Although the progress of the western and eastern sections has been sequential, they both face great difficulties. This is also the main reason for the long construction period.

Although the North Cross Passage and Yan'an Elevated Road are both east-west arteries, as the city develops to this day, the North Cross Passage faces larger building volumes and denser pipelines when crossing. Taking the eastern section as an example, Cai Yunfei, Deputy Commander of the New North Cross Passage Project of the Urban Investment Highway Group, said that the construction work of the eastern section is mostly located below the road, facing problems such as dense pipelines, narrow work areas, and difficult traffic organization. "Moreover, the underground section of the eastern section is composed of sandy silt and silty clay, which are unevenly distributed, have poor self-sufficiency, and are rich in water content, just like crossing in a rice jar, which further increases the difficulty of construction," he said.

On September 29 and December 10, 2021, two super large shield tunneling machines, the "Jiangong" and "Zongheng", participated in the construction of the eastern section of the North Cross Passage. They started from different working wells, headed towards each other, and after more than a year of twists and turns, they finally "met" at the Anguo Road Well. Even during the Spring Festival and important holidays, the project team and builders did not stop work and continued construction sprints.

Photo by Qi Yingpu

The Shanghai Construction Engineering project team responsible for the excavation of the "Jiangong" project introduced that the first difficult crossing construction in construction was successfully crossing the rail transit line 10 in January 2022, with a vertical distance of only 8.1 meters and 7.5 meters between the operating line 10 and the down line. In addition to being close, complex soil conditions are also one of the key difficulties in crossing, and there should be no deviation in shield tunneling posture and settlement control. In the process of crossing, the construction team simulates multiple scenarios, hires an expert team and develops a crossing plan, prepares detailed contingency plans, and conducts comparative verification one by one to determine the best construction plan.

One Road Driving Management and Technological Progress

According to the staff, the deepest position of the eastern section of the North Cross Passage is on Zhoujiazui Road and Gaoyang Road. The covering soil above the tunnel is about 30 meters, which is equivalent to the height of a 10 story building. So, will underground excavation disturb the surrounding area?

Yang Mingzhou, a 75 year old man who has been living along Zhoujiazui Road since the age of 4, has been very concerned about the construction progress of the North Cross Passage: "When building the North Cross Passage, the staff brought equipment to monitor our homes multiple times to ensure that our community was not affected."

Photo by Qi Yingpu

During the more than 8-year journey, the North Cross Passage not only drove effective investment and helped optimize the road network, but also comprehensively promoted management and technological progress in the engineering field of Shanghai, known as the "encyclopedia style bridge crossing the city".

The reporter learned from the Urban Investment Highway that the North Cross Passage Project has pioneered a management model in Shanghai that is "owner led, BIM professional consultation, and participation from all parties". It explores integrated BIM+GIS technology for construction, operation, and maintenance, achieving visual comparison of schemes, virtual assembly, design disclosure, and completion handover. Its advantage lies in higher construction efficiency and improved engineering quality.

BIM technology simulates tunnel operation

In the past, when constructing projects, we often encountered problems and thought about how to solve them. In the construction of Beiheng Hengfeng Corridor, this mode has changed from "meeting problems and solving problems" to "actively finding and solving problems". The construction site management platform created based on BIM technology incorporates various indicators such as settlement deformation, water level, dust, noise, and climate, achieving full process automation monitoring. All 28 elements of a "smart construction site" can be intelligently supervised on site. Its advantage lies in strengthening safety production control and further reducing engineering risks.

At the technical level, the comprehensive technology of micro disturbance construction has been developed and applied in the 14.7-kilometer tunnel from the west to the east section of the North Cross Passage, forming a typical case in the history of Chinese architecture where ultra large diameter shield tunneling passes through dense buildings in the central urban area.

The reporter found that as early as in the shield tunneling construction of the western section of the project, several domestic "firsts" were created in the unique soft soil layer of Shanghai. One of them is the "largest" in diameter and length. The diameter and length of the western tunnel section of the North Cross Passage Project are currently the largest among the underground tunnels built in the central urban areas of China; The second is the "most" of crossing buildings, with the North Cross Passage shield tunnel project currently having the most shield tunneling buildings in China; The third is to cross the "most" of subways. The entire North Cross Passage has crossed rail transit lines 13 times, and the western section of the project has completed 9 crossings. Among them, the shield tunneling of the main line of the North Cross Passage under the operating rail transit section tunnels of Line 11 and Line 7 is currently the project with the largest shield tunneling diameter among the underground operating rail transit section tunnels in China.

Remote monitoring and cruise control system for shield tunneling

In addition, the western section of the tunnel has also pioneered multiple processes nationwide, such as the use of plain concrete without decorative concrete technology. Cai Yunfei introduced that the eastern section will continue the design of the western section, and this technology will continue to be applied in the tunnel. The mechanical and electrical equipment will remain exposed and simple, replacing the traditional decoration of the tunnel with a natural texture, which is more low-carbon and energy-saving. Continue to adopt the scheme of stacking up and down lanes to maximize the intensive utilization of limited land resources and environmental friendliness in the central urban area.

The North Cross Passage will be fully completed and opened to traffic in 2024, becoming a fast new channel from the Hongqiao hub to the Pudong New Area, serving medium and long distance arrival and departure transportation in key northern areas, and affecting the intercity transportation network pattern of the Yangtze River Delta region. At that time, citizens can drive from Yangpu to Hongqiao Airport in just 30 minutes without traffic congestion, which greatly saves time compared to using the inner ring road in the past.