this morning
Nanjing Metro Line 4 Phase II
"New Journey", a river-crossing shield machine.
From the middle air shaft of Jiangxinzhou
Digging towards the north bank of the Yangtze River
Construction of river crossing section kicks off
Metro Line 4 Phase II project started at Pearl Spring East Station, along the Puwu Road, Dingshan Avenue Road walk, in turn, down through the Yangtze River, Qianzhou, Jiangxinzhou, clamping the river, and then connected to the first phase of the project starting station Longjiang Station.The total length of the line is about 10 kilometers, all of which are underground lines with 6 stations, including 2 interchange stations.
It is understood that from the middle wind well to the Jiangbei Civic Center Station shield interval line is 3062 meters long, for the single-hole double-line design, using a mud-water balanced shield machine construction. Shield machine in the Jiangxinzhou start, the top of the overburden thickness of about 26.8 meters thick.When crossing the Yangtze River, the deepest overburden thickness is 55.35 meters, which is the deepest subway line crossing the river in the Yangtze River Delta region.
The mud-water balanced shield machine named "New Journey" has an excavation diameter of 11.64 meters, a total weight of 2,100 tons and a total length of 120 meters.The "synchronized injection of two-liquid slurry technology" is the first time to be applied in the construction of domestic subway tunnels across the river, and it is the first time to be applied in the construction of subway tunnels across the river.It can effectively control the uplift of tube sheet, ensure the construction safety and efficiency, and improve the quality of formed tunnel.
The work of the mud-water balanced shield machine is mainly two parts: propulsion excavation and pipe piece assembling.There are two channels, one in and one out, on the cutter plate at the front of the shield machine. During the excavation process, the excavation surface injects the prepared slurry into the soil to be excavated through pressure to form a mud film; at the same time when the mud film is formed, the cutter plate rotates continuously to excavate the soil and mixes the excavated soil with the slurry to form a highly concentrated slurry, which will be transported out of the shield machine by the drainage pipe and entered into the ground for treatment by the mud-water separating system. The mud is transported out of the shield machine through the mud discharge pipe and into the mud-water separation system on the ground for treatment.
The shield machine stops every 2 meters it digs forward to assemble the prefabricated pipe pieces, and the entire tunnel is formed by connecting the prefabricated pipe pieces together in a ring.
The shield construction will pass through the powdery clay, fine sand, medium-coarse sand, rounded gravel and other strata of the Yangtze River Mangtan, and the biggest test is the need to pass through the middle-weathered muddy sandstone strata of about 700 meters long.As the most critical construction section of Line 4 Phase 2, the "New Journey" mud-water balanced shield machine will complete the most technically difficult part of the line.
Metro Line 4 Phase II project is the fourth river-crossing metro built in Nanjing after Metro Line 3, Line 10, Ning and Intercity Phase I. The project is expected to be completed by the end of this year. Upon completion, it can accelerate the promotion of Nanjing's cross-river integration and development, improve the city's rail transportation network, strengthen the connection between Nanjing's Jiangbei New Area and the main city, and ease the traffic pressure across the river.
