On the 29th, south of the intersection of Renmin East Road and Dongliu Road, the Bazihua shield-driven section of the Huangli Road access/exit segment of Changsha Metro Line 6, built by China Railway 12th Bureau Group, was successfully holed through, marking the full breakthrough of all shield tunnels on Line 6 and laying a solid foundation for the line's opening to traffic.

The Bazihua shield-driven section of the Huangli Road access/exit segment of Changsha Metro Line 6 is 1,123.8 meters long, with a cover depth of 5.7 to 13.5 meters. It adopts a "V"-shaped gradient and lies mainly in moderately weathered argillaceous siltstone strata. "The biggest risk source for the Bazihua shield-driven section is that it passes over the right line of the existing Shaolong section of Line 6 while passing under a drainage box culvert, crossing multiple gas pipelines, passing alongside high-voltage power towers, and involving continuous small-radius curve turning construction conditions," said Dai Tianqi, chief engineer of the Changsha Metro Line 6 project department of the Seventh Company of China Railway 12th Bureau Group.

Facing a series of risks and challenges, the project department held multiple special meetings to discuss and prepare relevant special construction plans and emergency response plans for safe construction; determined reasonable countermeasures for risk sources that might arise during construction; before the shield machine passed through buildings and structures, conducted technical briefings for all personnel, comprehensively evaluated the shield machine's cutters and cutterhead, carried out comprehensive equipment inspection and maintenance of supporting facilities, and strengthened the management of muck transport, effectively preventing shutdowns caused by shield machine failures during undercrossing.

"We started with muck conditioning, optimized the construction plan, improved the cutterhead and screw conveyor, strictly controlled and adjusted tunneling parameters, avoided adverse shield turning attitudes affecting segment assembly and shield tunneling, overcame difficulties such as severe cutter wear and jamming of the cutterhead and screw conveyor, and ensured continuous and stable tunneling," Dai Tianqi said. The project department undertook the construction tasks for three mined and shield-driven sections of Line 6 and ultimately achieved the successful breakthrough of all shield-driven sections.

A person in charge from Changsha Rail Transit Group introduced that Changsha Metro Line 6 is an east-west trunk line of Changsha and the line with the longest mainline mileage to date. The entire line crosses three major rivers, three key railways, three key expressways, and five existing metro lines, covers the city's east-west passenger flow corridor, strengthens the connection between the Hexi sub-center and the main center, links the Hexi intercity rail hub and Huanghua Airport, and will greatly ease east-west traffic pressure in Changsha and provide citizens with a more convenient and comfortable travel environment.

As of now, among the 34 stations on Line 6, the main structures of 33 stations have been topped out, all shield-driven sections have been holed through, and of the 323 ancillary structures along the line, 290 have started construction, of which 101 have been completed; the main structures of the parking lot underground passage, viaduct, comprehensive building, and car wash building have been completed, and construction is underway on the turnout area cover slabs, stabling depot, and locomotive adjustment engineering depot, among others.