On June 11, the world's longest and widest steel shell concrete immersed tube tunnel, the Shenzhen–Zhongshan Bridge subsea tunnel, successfully launched its final joint, accurately connected with the E24 pipe joint on the east side, officially closed the "Great Wall of the Seabed", and Shenzhen and Zhongshan City "officially joined hands" at the bottom of the Lingdingyang Ocean. The Shenzhen–Zhongshan Bridge is a national "13th Five Year Plan" Megaproject and the world's first two-way eight lane steel shell immersed tube tunnel. Compared with the immersed tunnels of the Hong Kong–Zhuhai–Macau Bridge, the construction of the immersed tunnels of the Shenzhen–Zhongshan Bridge faces many new problems, such as the new structural form of steel shells, the extra wide size, the extra long floating distance, and the long closure time of the channel. The design and construction of the immersed tunnels have created many world firsts again, providing a new "Chinese scheme" for the construction of the immersed tunnels across the sea in the world. The millimeter precision deep to medium channel achieved by aircraft carrier level immersed tubes is a core transportation hub project in the Guangdong Hong Kong Macao Greater Bay Area, with a total length of 24 kilometers. It integrates "bridges, islands, tunnels, and underwater interchanges" and is the most difficult cross sea cluster project to construct in the world today. Among them, the underwater tunnel is about 6.8 kilometers long, including a submerged pipe section of about 5 kilometers, consisting of 32 pipe joints and 1 final joint. The weight of the sunken tube is about 80000 tons, which is equivalent to the weight of a medium-sized aircraft carrier. Such a large and heavy component requires extremely high assembly level and installation accuracy to achieve high pressure and no leakage after being connected to the seabed, and the construction requirements are very strict. After repeated research, judgment and analysis, the final joint of the Shenzhen–Zhongshan Bridge submarine steel shell immersed tube tunnel is a wholly prefabricated underwater tube push out type, which is the world's first new structural device. The final joint weighs approximately 1600 tons and is placed inside the E23 pipe joint expansion section. On June 10th, after the floating installation of E23 pipe joint was completed, it was pushed out from one side to connect with E24 pipe joint. "Previously, the subsea immersed tube tunnel was closed, and the final joints were mostly constructed by hoisting. This innovative push out joint has the advantages of good safety, fast construction, no need for large equipment, and good economy." Ning Jinjin, executive deputy chief engineer of the Shenzhen–Zhongshan Bridge Project Department of CCCC First Harbor Engineering Co., Ltd., said. At 14:00 on the 10th, the final joint pushing operation was ready, and under the world's first "jack pushing+water pressure pushing" dual system, it slowly pushed out at a speed of 5mm to 10mm per minute. At 8:00 am on the 11th, the final joint achieved precise docking of the E24 pipe joint, and the "Underwater Great Wall" was officially closed. "In order to ensure the connection of the final closure section with high accuracy, Shenzhen–Zhongshan Bridge has realized the millimeter level installation accuracy of several pipe joints previously by using the Beidou positioning system and the sinking installation control system, creating a prerequisite." Ning Jinjin introduced that CCCC First Harbor Engineering Co., Ltd. worked with Guangdong Communications Group, design units, maritime and other units to overcome the complicated flow field at the dragon mouth, the limited working space, and the difficulty in floating and installing pipe joints The launch phase poses world-class challenges such as high difficulty in attitude control, and is the world's first to create a new process for the prefabricated underwater final joint of immersed pipes. The Shenzhen–Zhongshan Bridge not only has the seabed part, but also has considerable difficulty in the sea part to create the world record of rapid island formation. As an important transition between a long-span bridge on the sea and an extra long two-way eight lane subsea immersed tunnel, the West Artificial Island is the first project of the entire Shenzhen–Zhongshan Bridge. The area of the island above the sea level is equivalent to 19 standard football fields. Westerners