On April 22, the right-line shield tunneling of the section from Bolan Road Station to Sixin South Road Station (referred to as the "Bo-Si section") of Wuhan Rail Transit Line 12 successfully completed its reception.

According to reports, the Bo-Si section is 1,082 meters long in total. The right line has already been completed, while the left line has 165 meters remaining and is currently being excavated, with completion expected in May. After the Bo-Si section achieves dual-line completion, the two shield machines on the left and right lines will undergo maintenance and repair, and will then be launched again from the other end of Sixin South Road Station, tunneling toward Sixin Middle Road Station.

At Sixin South Road Station in Hanyang District, unlike other shield reception operations, a huge steel sleeve about 20 meters long is connected to the tunnel portal at the bottom of the station. At this point, the shield machine has completed excavation and is "standing by" behind the portal.

▲ Using the steel sleeve reception process, construction workers weld and seal the tunnel portal.

On site, construction workers are welding and sealing the tunnel portal; once sealing is complete, the steel sleeve will be dismantled. The construction workers completed the dismantling of the steel sleeve, and the shield machine successfully exited the tunnel.

According to reports, because the site is located on the first-level terrace of the Yangtze River where groundwater is abundant, the shield reception for the Bo-Si section was decided to adopt the steel sleeve process for safety reasons.

"The steel sleeve process, simply put, involves installing a steel sleeve outside the shield machine to form an enclosed space, creating a pressure environment for the shield machine as it traverses the soil layer. After welding to seal the tunnel portal, soil is filled into the steel sleeve so that the shield machine is in a simulated safe soil environment and slowly excavates out of the tunnel." According to reports, this process can effectively avoid risks such as water and sand ingress when breaking through the tunnel portal.

The Third Bid, First Work Zone of Line 12 (Jiangbei Section) includes 2 stations and 3 sections: the main structures of both Bolan Road Station and Sixin South Road Station have been completed; the section from Bolan Road Station to Guobo Center South Station has achieved dual-line completion; the section from Bolan Road Station to Sixin South Road Station has completed the right line, with the left line expected to be completed in May; and the section from Sixin South Road Station to Sixin Middle Road Station is about to be launched.

Bolan Road Station is 306.5 meters long and 20.3 meters wide at the standard section. It is an underground two-level island-type station located at the intersection of Sixin South Road and Bolan Road Second Lane, approximately 2.1 kilometers in a straight line from the Yangtze River. Walking into the station concourse, one sees fair-faced concrete walls and a dry floor—no small feat for an underground station so close to the Yangtze River.

▲ Line 12 Bolan Road Station uses multiple processes to create a "leak-free" station.

Fang Shitao, deputy supervisor of the Quality and Safety Supervision Department of Wuhan Metro Group, introduced that because Bolan Road Station is located on the first-level terrace of the Yangtze River where groundwater is abundant, a "multi-pronged" approach was adopted during construction to deal with seepage and leakage. When pouring concrete for the main structure of the station, construction workers paid attention to the rebar cutting dimensions and installation process at locations with dense reinforcement such as beam-column joints and main beam-to-concealed beam joints, considered the insertion positions of vibrators in advance, and strengthened concrete vibration control; after concrete pouring, the formwork removal process was strictly controlled, and supports could not be removed blindly to avoid the structure being loaded too early and causing cracks; grouting and joint filling were carried out—after the structure construction was completed and reached design strength, grouting and joint filling were performed behind the side walls to ensure density behind the walls.

▲ The Bo-Si section of Line 12 uses a steel sleeve to receive the shield machine.

"The biggest feature is the use of embedded grouting pipes, which was relatively rare in previous metro construction," Fang Shitao introduced. A total of 41 embedded grouting pipes were installed throughout the station, effectively preventing seepage and leakage.

Sixin South Road Station is located at the intersection of Sixin South Road and Jiangcheng Avenue, arranged along the south side of Sixin South Road, and will interchange with the planned Line 10 in the future. At present, the main structure of Sixin South Road Station has been topped out, and construction is underway on the crown beam supports for the reserved interchange space for Line 10.