Wuhan Metro Line 12 Ding-Shi Section Shield Machine Precisely Breaks Through

On July 11, as the final tail shield segment of the "Pioneer" shield machine was lifted out at Shilipu Station, the tunnel of the Ding-Shi section (Dingjiazui Station–Shilipu Station) of Wuhan Metro Loop Line 12 achieved dual-line breakthrough. A breakthrough was made in the construction technology for the shield machine successfully undercrossing the existing station and retaining piles.

According to reports, this section is a key and difficult control project of Wuhan Metro Line 12. In a shield section of only 870 meters, the shield machine had to successively face three major challenges: boring hard rock, passing under bridges, and crossing stations. To effectively reduce tunneling risks and ensure construction quality and progress, the contractor repeatedly demonstrated and verified the plan and joined hands with the manufacturer and research institutes to enable the shield machine to achieve sufficient power, wear resistance, and high flexibility in complex geological environments, and to "handle both soft and hard ground" and bore through in one go.

Boring hard rock. After advancing 150 meters, the shield machine encountered a 274-meter section of moderately weathered quartz sand hard rock with a strength of 214 MPa, and tunneling was like drilling a hole in a steel plate. The contractor promptly replaced the cutterhead and equipped it with full-face disc cutters whose blade compressive strength reached 2,800 MPa, achieving "cutting iron like mud," and broke through the encirclement in one month.

The final tail shield segment of the "Pioneer" shield machine was lifted out at Shilipu Station, and the dual-line tunnel of the Ding-Shi section achieved breakthrough.

Passing under bridges. When the shield machine side-crossed the Second Ring Road elevated bridge, the minimum horizontal distance from the bridge piles was only 1.8 meters, and tunneling was like walking a tightrope—a slight mistake would cause deviation from the alignment. Before the crossing construction, a trial section was set up to derive the optimal shield tunneling parameters and reduce disturbance to the bridge piles from tunnel construction. An automated monitoring system was used to monitor pier settlement data changes in real time, and manual re-inspection was conducted to monitor changes in the tunnel structure, completing the side-crossing bridge construction with nearly zero settlement.

Crossing stations. To avoid disturbance to Line 4 operations from shield undercrossing vibrations, the shield machine tunneled during the maintenance window from 0:00 to 4:30 a.m. During tunneling, intelligent robots scanned the entire process and submitted a monitoring result every half hour; the shield machine adjusted tunneling parameters based on the monitoring results and smoothly crossed Line 4 in 5 days, with no abnormalities in the station structure. This created a precedent for a Wuhan Metro shield machine fully undercrossing a single station and provided a safer and more efficient reference method for subsequent line construction.