At 20:08 on September 15, the E9 tube section of the Dalian Bay Subsea Tunnel, constructed by CCCC First Harbor Engineering Co., Ltd., was successfully installed, achieving more than half in both the number of tube sections installed and the mileage. According to the plan, three more tube sections, E10 to E12, will be installed in the following two-plus months, and this year's immersed tube installation work for the Dalian Bay Subsea Tunnel is expected to conclude by the end of November.

The E9 tube section installed this time is a standard tube section, 180 meters long, 33.4 meters wide and 9.7 meters high, weighing about 60,000 tonnes. The immersed tube installation is difficult to control and requires high precision; the placement position was entirely in silt geology for the first time, posing challenges to leveling and immersed tube installation construction.

The surplus water depth at the tail end of the E8 tube section was relatively shallow. To prevent the E9 tube section from colliding with the E8 tube section during mooring operations, the project team optimized the construction plan, changing the mooring position from 20 meters to 50 meters from the E8 tube section, minimizing mooring risks to the greatest extent. The floating transport and installation work started at 6:00 that day. After successively completing processes such as tugboat formation, floating transport, mooring and installation, the connection with the E8 tube section was successfully completed at 20:08 that day, taking nearly 14 hours. Measurement and control data show that the installation precision of the E9 tube section meets the design requirements. As of now, 1,575 meters of the subsea section of the Dalian Bay Subsea Tunnel have been completed, and the total length of the immersed tube section is 3,035 meters; 9 tube sections have been installed out of a total of 18.

On the same day, the E12 tube section of the Shenzhen-Zhongshan Link, constructed by CCCC First Harbor Engineering Co., Ltd., was successfully connected with the E11 tube section, bringing the length of the immersed tube tunnel to 2,062.3 meters and breaking through the 2,000-meter mark. This is a new record in the field of world cross-sea corridor construction set by the two cross-sea immersed tube tunnels in the north and south, after the first simultaneous "double tube" operation last December.

From December 9, 2020, when the first immersed tube section was lowered to the seabed and accurately connected with the buried section on the north bank, to September 15, 2021, when the E9 tube section was successfully installed, the Dalian Bay Subsea Tunnel successfully installed 9 immersed tube sections in just over 9 months, setting the shortest record in China for the installation cycle of 9 tube sections.

During the immersed tube connection process, as China's first dedicated construction vessel group for immersed tube floating transport and installation, "Jin'an 2" and "Jin'an 3" played an indispensable role. After the immersed tube installation project of the Hong Kong-Zhuhai-Macao Bridge subsea tunnel ended in 2018, the construction vessel group came to the Dalian Bay Subsea Tunnel after half a year of performance optimization and modification. The construction party achieved unified control of the two professional installation vessels, which on the one hand increased coordination and installation efficiency, and on the other hand increased operational precision, ensuring that the immersed tube installation precision reaches the millimeter level and ensuring that the Dalian Bay Subsea Tunnel is built as a century project.

In addition to "Jin'an 2" and "Jin'an 3", there are also the leveling vessel "Jinping 1" and the supply vessel "Banhe 7". These four vessels form the core vessels of the Dalian Bay Subsea Tunnel immersed tube installation project.