On the 31st, the ultra large diameter shield tunneling machine "Jianghai" with a maximum excavation diameter of 16.64 meters, jointly built by China Railway Construction Heavy Industry Group and China Railway 14th Bureau Group, was launched in Changsha, Hunan. This is the largest diameter shield tunneling machine independently developed by Chinese researchers. After going offline, it will be applied to the construction of the world's longest underwater shield tunnel for highways - the Haitai Yangtze River Tunnel. The Haitai Yangtze River Tunnel is located in the estuary area of the Yangtze River in Jiangsu Province. The total length of the project route is 39.07 kilometers, and the length of the cross river tunnel is 11.185 kilometers. It adopts the design standard of a two-way six lane expressway with a design speed of 100 kilometers per hour. Among them, the shield tunnel section is 9315 meters long and has a maximum excavation diameter of 16.64 meters. Along the construction route, it is necessary to cross complex geological zones such as silty clay interbedded with silt and fine sand composite strata. In addition, the maximum burial depth of this section of the tunnel is about 75 meters, with a maximum water pressure of 7.5 bar. It has the characteristics of ultra long distance, ultra large diameter, ultra high water pressure, ultra large burial depth, and complex working conditions. Song Huan, Senior Engineer of the Haitai Yangtze River Tunnel Project of China Railway 14th Bureau, stated that ensuring the continuous excavation of 9315 meters of the entire machine in complex underwater environments while maintaining high performance loads is the main challenge and difficulty faced by the development team. Fan Ruiqiang, a senior engineer at China Railway Construction Heavy Industry Group's TBM Research and Design Institute, introduced that in response to the construction risks and difficulties of the project, the team has carried out targeted design on key components such as the cutterhead, cutting tools, and main drive. The main drive is equipped with a telescopic function and a drive status monitoring system, effectively avoiding overloading of the main bearing caused by abnormal force on the cutterhead in special circumstances, facilitating tool changing operations, and assisting the cutterhead in getting out of trouble. At the same time, the team designed the external dimensions and structural thickness of the shield body according to local conditions, as well as increased the specifications of the oil cylinder, optimized the mud circulation system and grouting system, further strengthened the overall performance of the machine, and configured an intelligent assembly system for pipe connecting components to meet the construction needs of the project. (New Society)