As the cutterhead featuring Peking Opera facial makeup patterns slowly rotates, the East 6th Ring Road reconstruction project reaches a key milestone——the domestically largest-diameter shield machine “Jinghua” has completed debugging and started trial operation, creating conditions for the launch of the shield machine on the west line of the tunnel. It is expected that by the end of March, the shield machine will be launched from the north end of the tunnel, and the tunnel of the East 6th Ring Road reconstruction project will officially begin shield tunneling.

At the construction site of the East 6th Ring Road reconstruction project, rows of shield tunnel segments have been stacked on the open ground. Walking to the launch shaft and looking down, the huge shield machine is already lying underground, waiting for the excavation order, with its frontmost cutterhead already drilled into the soil. Entering the launch shaft along the safety stairs, the interior of the shield machine is very spacious, allowing five or six people to walk side by side.

The approximately 7.4-kilometer tunnel section of the East 6th Ring Road reconstruction project will be constructed using the shield method. The tunnel section adopts a separated double-tube layout, with two super-large-diameter composite slurry balance shield machines, “Jinghua” and “Yunhe,” purchased for the left and right lines respectively. The west line will be excavated by “Jinghua,” and the east line by “Yunhe.” At the end of March this year, “Jinghua” on the west line will be launched first. After an interval of one and a half months, “Yunhe” on the east line will also be launched. The two shield machines will be spaced 200 meters apart in the future, tunneling through the two tunnels one after the other.

The diameter of shield machines used for subway tunneling is generally 6 to 7 meters, while “Jinghua” and “Yunhe” use domestically produced 16-meter-class super-large-diameter slurry balance shield machines, which are the largest-diameter shield machines in China to date.

With a larger excavation area, the amount of excavated soil also increases exponentially. According to reports, the shield section of the East 6th Ring Road tunnel produces 202 cubic meters of excavated soil per linear meter, placing higher demands on the stability of the excavation face and the adaptability of the shield machine. To this end, the shield machine adopts overall independent design and system integration technology, equipped with multiple core technologies such as atmospheric cutter replacement, telescopic main drive, efficient transportation and assembly technology for super-large-diameter heavy-duty segments, and a super-high-power slurry circulation system.

In response to the soft soil strata in the Tongzhou area, the tunnel also adopts a synchronous dual-liquid grouting system, reducing the setting time from 8 hours to less than 1 hour, enabling rapid and stable tunnel construction and avoiding surface settlement.

“This tunnel on the East 6th Ring Road is not only the first expressway tunnel in Beijing to use shield construction, but also the first tunnel in China to set up an evacuation and rescue passage below the traffic lane,” introduced the head of the engineering department. The tunnel of the East 6th Ring Road reconstruction project is divided into three levels: the upper level is the smoke exhaust passage, the middle level is the traffic lane, and the lower level is the evacuation and rescue passage. In the future, an escape opening will be set up every 100 meters in the tunnel. In case of danger, drivers and passengers can go down the stairs from the escape passage into the rescue passage. In addition, the rescue passage also has driving conditions, and rescue vehicles can also use the rescue passage to reach designated locations for convenient rescue.

On-site construction personnel introduced that during the Spring Festival this year, more than 100 migrant workers and management personnel will stay at the construction site, and the site will be under closed management. During the Spring Festival, workers will continue to patrol and inspect the site and make minor adjustments to the shield machine as needed. “The project department has also prepared a variety of activities for the retained personnel, such as watching movies and holding entertainment activities on site, so that everyone can spend a warm Spring Festival in Beijing,” introduced the relevant person in charge.

It is understood that the East 6th Ring Road reconstruction project is a key project for implementing the Beijing Master Plan and the Regulatory Detailed Plan for the Beijing Municipal Administrative Center. The East 6th Ring Road reconstruction project starts from the Jingha Expressway Interchange in the south and ends at Luyuan North Street in the north, with a total length of about 16.3 kilometers. The project is divided into two parts: direct widening and underground reconstruction. The widened section is 7.1 kilometers long, and the underground section extends from the south side of Jingjin Highway to the north side of Luyuan Second Street, with a tunnel length of 9.2 kilometers. The tunnel adopts a combination of open-cut and shield methods, with a single shield drive length of 7.4 kilometers.