(shield workers of Zhanjiang Bay Subsea Tunnel are lifting segments.) At 10:00 on September 13, the "Yongxing" shield machine of the Zhanjiang Bay undersea tunnel of Guangzhou Zhanjiang High speed Railway successfully crossed the main channel of Zhanjiang Bay after 19 days, during which there was no impact on the main channel of Zhanjiang Bay. This marks that the Zhanjiang Bay undersea tunnel has successfully overcome new technical difficulties and made breakthrough progress. Entering the Smart Command Center of Zhanjiang Bay Submarine Tunnel through the lowest water depth of the main channel, from the demonstration screen, the "Yongxing" shield machine with a total length of 147 meters is like a "steel dragon" driving toward the seabed, crossing the lowest water depth of the main channel of Zhanjiang Bay. "The main channel of Zhanjiang Bay is the first level risk source in the Zhanjiang Bay undersea tunnel project, and also the deepest crossing." Wang Hao, the shield manager, introduced that the water pressure under the main channel of Zhanjiang Bay is greater, and the pressure bearing performance of the shield machine in long-distance tunneling at the lowest point of the seabed is facing a huge test. At the same time, with the extension of the tunneling mileage, technical problems such as material transportation, tool wear and tool change, mud pipeline explosion-proof, shield tail seal safety, long-distance ventilation and so on need to be solved one by one under the conditions of ultra long-distance seabed tunneling. The main channel of Zhanjiang Bay Subsea Tunnel that passes through this time is 195 meters long. It is the most important marine transportation line in Zhanjiang Bay. The maximum water depth is 20.8 meters, the lowest point is 16.7 meters covered with soil, and the maximum water pressure is 6 bar. It is equivalent to bearing 6 kilograms of pressure on an area the size of a fingernail. The construction is very difficult and risky. In order to successfully realize the "Yongxing" shield machine crossing the main channel of Zhanjiang Bay, the project will strengthen the offshore monitoring and in tunnel monitoring, and invite shield experts to check and discuss the technical scheme, so as to ensure that the shield tunneling task can be completed with the fastest speed and the smallest disturbance. During the crossing of the main channel, a strict construction plan and emergency response plan shall be formulated, and all data and parameters of the "Yongxing" main channel in Zhanjiang Bay shall be monitored in real time through the smart command center to ensure safe and stable crossing. At present, the "Yongxing" shield tunneling machine has accumulated a footage of 2770 meters, completed the assembly of 1385 ring roads, and entered the sea area for more than 1300 meters, successfully crossing the deepest part of Zhanjiang Bay. It is expected to complete the overall excavation of the sea area by the end of the year. Guangzhou Zhanjiang High speed Railway is an important part of the national "eight vertical and eight horizontal" high-speed railway network. The total length of the main line is about 401 kilometers, the total investment is estimated to be 99.8 billion yuan, and the design speed is 350 kilometers per hour. It is the longest and the largest high-speed railway project in Guangdong Province. As a control project of the whole Guangzhou Zhanjiang railway, Zhanjiang Bay Subsea Tunnel has a total length of 9640m and is a single tunnel double track structure, including 7551m shield section, 14.33m shield excavation diameter and 13.8m segment outer diameter. It is the longest sea crossing high-speed railway shield tunnel in China at present. The successful crossing of the Zhanjiang Bay Subsea Tunnel through the main channel marks the "acceleration" of the construction of the Guangzhou Zhanjiang high-speed railway project, and also means that Zhanjiang's access to the national "eight vertical and eight horizontal" high-speed railway network has taken a substantial step forward. After the opening of Guangzhou Zhanjiang High speed Railway, it will realize 90 minutes' mutual access from the central urban area of Guangzhou to the central urban area of Zhanjiang, and become an important part of the high-speed railway corridor connecting the Guangdong Hong Kong Macao Greater Bay Area, Hainan Free Trade Port, and the Beibu Gulf urban agglomeration