Schematic diagram of the Phase I route of Qingdao Metro Line 9.

On August 8, as the cutterhead of the "Municipal Iron Army No. 5" shield machine slowly rotated, the left-line shield machine for the section between Huacheng Road Station and Chengzi Station (referred to as the Huacheng section) of Qingdao Metro Line 9 successfully launched, marking that the Huacheng section has officially entered the shield construction stage and embarked on a new journey of tackling key challenges.

It is understood that the "Municipal Iron Army No. 5" shield machine has an overall length of 67.5 meters, an excavation diameter of 6.46 meters, and a total weight of approximately 380 tons. This shield machine undertakes the left-line tunneling task, running east-west along Zhengyang Middle Road, the main artery of Chengyang District. It launches from the small-mileage end of Huacheng Road Station and tunnels to the large-mileage end of Chengzi Station for reception and lifting out. The section has a total length of 883 meters, with a tunneling rate of about 200 meters per month, and is expected to be completed by the end of December. The Huacheng section accounts for only one-twentieth of the total length of the Phase I route of Qingdao Metro Line 9, yet it faces the most difficult challenge in the Phase I construction of Line 9. The shield machine needs to pass beneath the Aimin River Bridge, which is located in a fully water-rich sand layer, and pass alongside the bridge piles of the Qingdao-Yinchuan Expressway at a spacing of 1.9 meters, placing extremely high demands on key technologies such as shield guidance measurement, slag discharge control, pressure maintenance control technology, and simultaneous grouting. Therefore, the turning radius and attitude control of the "Municipal Iron Army No. 5" shield machine can be described as "pushing the limits," with construction difficulty increasing exponentially.

"We invited renowned shield, geology, and equipment experts to demonstrate and review the control measures for launching, tunneling, and under-passing environmental risks, as well as the equipment modification plans, five times in total," it was introduced. At the same time, the project department prepared special emergency plans for risk points during tunneling and strictly conducted safety and technical disclosure training to ensure that the shield plan is safe and controllable.

It is reported that the "Municipal Iron Army No. 5" is the second shield machine on the entire Line 9. As the project progresses, shield equipment will successively enter the site and launch. The entire line plans to deploy 12 shield machines and 2 TBM tunneling machines, which will greatly improve construction efficiency. After the completion and operation of Metro Line 9, it will accelerate the integrated development of Chengyang District and the East Coast Central Urban Area, and is of great significance to improving the network structure of the Qingdao metropolitan area and building a "Qingdao on Rails."