Recently, waves rippled across the water surface in the shield receiving shaft of the entry line of the northern extension of Guangzhou Metro Line 8 beside Yagang Avenue in Baiyun District, as a shield machine slowly emerged from the water, announcing the successful breakthrough of the tunnel on the entry line of the Baiyun Lake Depot section of the northern extension of Line 8. This is also the first time in Guangzhou Metro's history that a shield machine has performed a "water exit."

In previous metro shield construction, after departing from the launch shaft, the shield machine would bore into a reinforced shield receiving shaft, where it would then be dismantled and hoisted to the surface. However, the shield machine on the entry line of the Baiyun Lake Depot section of the northern extension of Line 8 was received in water.

The shield machine on the Baiyun Lake entry/exit line of the northern extension of Line 8 was a typical case of "shallow-buried, large-slope shield exit," with the portal end buried at a depth of only 1.3 meters. Because the geological environment around the receiving shaft was complex and pipelines were densely distributed around the shaft, the effectiveness of end reinforcement was difficult to guarantee. After comparing various receiving methods, metro construction personnel decided to adopt a special underwater backfill receiving method, actively backfilling the shield receiving shaft with water and using the mechanism of balancing water and soil pressure inside and outside the shaft to control portal leakage. By controlling the water level to expose the upper arc of the cutterhead, they could both prevent a large influx of groundwater and soil from the open portal during exit that could cause engineering hazards, and observe the precise position of the cutterhead as in ordinary receiving methods, achieving precise stroke control and flexible emergency management, safely pushing the shield machine into the receiving shaft under "visible" conditions.

As of now, the civil engineering works of the northern extension of Line 8 have been completed 72% cumulatively, and the Baiyun Lake Depot has been completed 92% cumulatively. Of the 15 stations, Cultural Park Station was completed together with Line 6, 12 stations have had their main structures topped out, and Caihongqiao and Xicun stations are under civil construction. Of the 15 running tunnels, 7 have achieved dual-line breakthrough, 8 are under civil construction, and a total of 14 shield machines are tunneling.