Core Points - The completion of the ballastless track construction for the Shantou Bay underwater tunnel marks a significant milestone for the Shantou-Shenzhen High-Speed Railway, which is part of China's "Eight Vertical and Eight Horizontal" coastal high-speed rail network [1] - The Shantou-Shenzhen High-Speed Railway is a key project in Guangdong Province and will connect with the under-construction Zhangshan High-Speed Railway, enhancing the north-south rapid passenger transport corridor between the Pearl River Delta and the Yangtze River Delta [1] - The project is expected to promote the integration of cities along the route into the Guangdong-Hong Kong-Macao Greater Bay Area and strengthen connections with the East China region [1]