On June 23, as the cutterhead smoothly broke through the wall, the double-line tunnel of the Guoxiang West Road Station to Binhai West Station section (hereinafter referred to as the Guobin section) of the Phase I project of Rail Transit Line B1, constructed by the Second Company of China Railway Tenth Group, was successfully holed through, successfully "joining hands" with Line Z2 at Binhai West Station. This marks important progress in the construction of Rail Transit Line B1 and lays a solid foundation for the advancement of subsequent works.

The Guobin section tunnel has a total length of 1.1 kilometers and was excavated using an earth pressure balance shield machine with a diameter of 6.8 meters. The minimum clear distance between the outer diameters of the left and right segment rings of the tunnel is only 3.5 meters, and the small-clearance section is as long as 220 meters, posing great challenges to the shield tunneling operation. Faced with the "small clear-distance construction" challenge, the rail company organized the project to balance "left and right" and achieve precise control. The right-line tunnel was constructed first, and a test section was established to adjust tunneling parameters, understand the stratum conditions, and summarize experience to guide the excavation of the left line. Through deep-hole grouting, the stratum was reinforced to ensure minimal disturbance; the 2-meter range around the tunnel was reinforced to strengthen the connection between the tunnel and the stratum, ensuring the combined action of the surrounding grout, soil layer, and tunnel structure.

In addition, the project made full use of the real-time attitude data provided by the shield machine's fully automatic guidance system, recorded data changes and adverse geological conditions during construction one by one, controlled the shield tunneling parameters, and maintained the shield attitude; conducted portal probing inspections on the receiving portal to check for water and sand inflow, and arranged auxiliary dewatering wells according to conditions to lower the water level to a safe range. At the same time, grouting pumps and related emergency rescue materials were prepared, and multiple measures were taken to ensure the safe reception of the shield machine.