At 10:16 on April 18, at the construction site of the Suzhou East Tunnel beside Yangcheng Lake, as the "launch" command was issued, the cutterhead of the "Tongyong Yuanmeng" shield machine of China Railway 14th Bureau began to rotate slowly, marking the official start of shield tunneling on the Suzhou East Tunnel of the Nantong-Ningbo High-Speed Railway—China's longest urban high-speed railway tunnel—and a major advance in the project's construction.

The Suzhou East Tunnel is one of the controlling works of the Nantong-Ningbo High-Speed Railway. The northern portal is located on the north side of the Beijing-Shanghai High-Speed Railway in Suzhou Industrial Park, and the southern portal is on the south side of Changbang Road in Wuzhong District, Suzhou. With a total length of 15.57 km and a single-tube, double-track design, it is China's urban high-speed railway tunnel with the highest construction standards and the longest mileage for 350 km/h operation.

The shield tunneling is carried out in close proximity to Yangcheng Lake, where the groundwater system is abundant. The super-large-diameter shield construction must successively pass beneath 3 railways, 2 metro lines, 4 rivers and lakes, more than 20 important municipal roads, and numerous structures and buildings, traveling long distances through soft soil and high-water-pressure, highly permeable sandy strata, with a maximum burial depth of 58 m and a maximum water and soil pressure exceeding 8 bar, placing high demands on the overall sealing performance, reliability, and parameter and attitude control of the shield machine.

To ensure long-distance, safe and efficient tunneling, the "Tongyong Yuanmeng" super-large-diameter slurry shield machine—currently the most intelligent of its kind in China—was tailor-made. With an excavation diameter of 14.81 m, a total length of 134 m, a total weight of 4,200 t, and an installed total power of 10,000 kW, the machine adopts a number of China-leading core technologies, including an advanced geological prediction system, a retractable main drive, an automatic cutterhead and cutter monitoring system, simultaneous two-component grouting, a high-pressure-resistant shield tail, an integral fully precast box culvert, and simultaneous pushing and segment erection, and has been specifically improved in cutterhead structure, cutter types, drive sealing, and pressure and corrosion resistance.

Launching a large-diameter shield machine under extremely shallow cover is one of the important risk points of this shield construction; the cover at launch is only 1.39 m thick, less than 0.1 times the tunnel diameter. To ensure launch safety, the project adopted a combination of "high-pressure jet grouting piles + mixing piles + U-shaped plain concrete diaphragm walls" to reinforce the launch portal, and used a "portal frame structure of uplift-resistant piles + reinforced concrete slabs" to control the shield machine's upward movement, ensuring the safe and smooth launch of the "Tongyong Yuanmeng" and accumulating successful experience for extremely shallow-cover launching and anti-uplift construction of super-large-diameter shields in China.

The Nantong-Ningbo High-Speed Railway is an important component of the coastal corridor of China's "Eight Vertical and Eight Horizontal" high-speed railway network and holds a very important position in the network. Once completed, the project will connect with multiple lines including the already operational Yancheng-Nantong High-Speed Railway, Beijing-Shanghai High-Speed Railway, Shanghai-Nanjing Riverside High-Speed Railway, Shanghai-Kunming High-Speed Railway, and Ningbo-Taizhou-Wenzhou High-Speed Railway, further improving the layout of the road network in the Yangtze River Delta region and holding great significance for advancing high-quality integrated development of the Yangtze River Delta.