In the early hours of March 10, as the shield machine's cutterhead broke through the final barrier and emerged safely, the left line of the section from Nanyuan Station to Duantang Station of the TJ8115 bid of Ningbo Metro Line 8 was successfully holed through. At this point, all shield-driven sections of the Ningbo Metro Line 8 TJ8115 bid project, constructed by China Railway Long Engineering Group Co., Ltd., have been fully holed through.

The project comprises a total of 4 shield-driven sections, of which the left line of the Nanduan section was launched on December 6, 2023. This line has a total length of 856.317 meters and successively passes beneath a DN2000 sewage pipe, Huancheng South Road, Shunde Road, the Yin-Feng Road Fire Rescue Station in Haishu District, Yujia River, a 10KV power drag pipe, a 160 gas pipe, and others. There are multiple risk points along the route; in particular, the hydrogeological conditions at the receiving end of Duantang Station are severe, with confined pore water present and close hydraulic connections, making the risk especially prominent. Under such conditions, the slightest carelessness in shield tunneling could lead to water and sand ingress into the tunnel, or even ground collapse and other extreme hazards.

To ensure safe tunneling by the shield machine, the China Railway Long TJ8115 bid project department arranged dedicated personnel for 24-hour duty and maintained high-density monitoring. They closely monitored settlement changes of the ground and surrounding buildings as well as the various parameters of the shield machine, promptly adjusted the tunneling parameters, and ensured the efficiency and quality of shield tunneling. They also sampled and analyzed the muck, while performing simultaneous grouting and secondary grouting inside the tunnel, strictly implementing dual safety and quality control measures. Before the shield machine's reception, China Railway Long specially dispatched a technical team to station on site, and Ningbo Metro Company organized 4 expert review meetings. Through the joint efforts of all parties, the shield reception plan was continuously improved and optimized, and special reinforcement and emergency measures were formulated especially for the formation characteristics at the Duantang Station reception. Owing to appropriate safety measures and effective shield support, the major risk of reception in the confined-water silty sand formation was overcome and resolved, and the line achieved smooth holing-through. Together with the other shield-driven sections previously holed through, the China Railway Long TJ8115 bid project department completed the main construction of the project section efficiently, safely, and with high quality on schedule.