On August 26, as the cutterhead began to rotate slowly, the "Yong'an No. 1" shield machine of China Railway 14th Bureau successfully launched for Section TJ7026 of Ningbo Rail Transit Line 7. This marks the first time China Railway 14th Bureau has entered Ningbo's rail transit sector for shield tunneling construction.

The construction scope of Section TJ7026 of Ningbo Rail Transit Line 7 covers the running tunnel between Minghai Avenue Station and Yufan Road Station. The left line is about 2,884 meters long, and the right line is about 3,284 meters long. The tunnel mainly passes through silt, silty clay, and fine sand strata. During construction, the shield machine is prone to floating and dipping. The tunnel passes alongside multiple high-voltage power towers, beneath three demolished-and-rebuilt bridge areas, four rivers, one box culvert, one ring expressway viaduct, and one East Outer Ring interchange bridge, making construction highly challenging.

According to the construction plan, shield tunneling in this section involves four shield launches and four shield receptions. To ensure smooth shield construction, the construction team configured two brand-new earth pressure balance shield machines specifically for this section, both with an excavation diameter of 6.76 meters. The shield machines are equipped with spare grouting and drilling holes at the bulkhead, enabling advanced drilling and grouting reinforcement. They are also equipped with an automatic shield tail clearance measurement system, an automatic segment layout system, a belt conveyor muck weighing system, and a synchronous grouting slurry weighing system, enabling continuous long-distance tunneling. The overall design is adaptable to the tunneling strata and can address engineering risks under various complex conditions.

▲Cutterhead of "Yong'an No. 1" lowered into the shaft

The "Yong'an No. 1" shield machine launched this time is responsible for the right-line tunneling task between Minghai Avenue Station and Yufan Road Station. To ensure the smooth launch of the shield machine, the construction team advanced construction and production work in an orderly manner, conducted multiple detailed inspections and surveys of the ground around the tunneling route, and invited experts to review and improve the plan. In only 18 days, they completed key procedures such as shield machine hoisting, assembly, and joint commissioning and testing to high standards.

▲Launch ceremony of "Yong'an No. 1"

"Next, we will strictly control shield tunneling parameters, shield tunneling attitude, shield advance speed, and cutterhead rotation speed to complete the construction task with quality and quantity guaranteed," said the project leader at the shield launch ceremony. The project team will carry out construction in strict accordance with the relevant standards and specifications of Ningbo Rail Transit Group to ensure high-quality completion of the section.