China's fastest-designed metro line, Guangzhou Metro Lines 18 and 22, entered the shield tunneling phase on August 29. Once completed, a metro trip from the Nansha Free Trade Zone to Guangzhou East Station in the city center will take only 30 minutes.
Guangzhou Rail Transit Lines 18 and 22 run in a “Y” shape, with the two lines merging at Panyu Square Station from north to south into a shared section. The two lines have a total length of 93.7 kilometers, of which Line 18 is 62.7 kilometers long with 9 stations, and Line 22 is 31 kilometers long with 6 stations. The project involves a total investment of 76 billion yuan (RMB), with a design speed of 160 kilometers per hour, making it the fastest-designed metro line in mainland China at present.
The project will open in two phases, with trial operation planned for the end of December 2020 and the end of December 2022. The entire line is planned to adopt an express-and-local operation mode of “limited-stop + all-stop” services.
According to the plan, both Lines 18 and 22 are positioned as regional express lines, with Line 18 as the Nansha Express Line and Line 22 as the South Station Express Line. The two lines connect four major hubs: Wanqingsha, Guangzhou South Station, Guangzhou East Station and Bai'etan, and radiate to three major hubs: Pazhou, Guangzhou Railway Station and Baiyun Airport.
According to the introduction, Lines 18 and 22 have four major features: high time-space targets, fast design speed, many interchange stations and long intervals. The two lines serve the function of rapidly connecting the Nansha New Area with the core area of Guangzhou; they are currently the fastest-designed metro lines in mainland China and can quickly disperse passenger flows; more than half of the stations on the two lines are interchange stations, with 8 of the 9 stations on Line 18 being interchange stations and 4 of the 5 stations on Line 22 (with 2 more reserved) being interchange stations; the average station spacing of the two lines is 7.6 kilometers and 4.2 kilometers respectively, with the largest station spacing at 25.9 kilometers.
The shield machine launched on August 29 is “fatter” than ordinary shield machines. This 8.8-meter-diameter shield machine, custom-built by China Railway Construction for Guangzhou Metro, expands the inner diameter of the tunnels on Lines 18 and 22 to 7.7 meters.
To ensure the safety of sound pressure and air pressure when trains pass at high speed, a sufficient safety distance must be left between the train and the tunnel. Simulation tests have shown that a tunnel with an inner diameter of 7.7 meters can ensure safe operation at 160 kilometers per hour. The civil engineering phase of Lines 18 and 22 has now begun, and many construction challenges remain to be overcome, such as complex geological conditions, the difficulty of passing under 11 rivers, and the construction difficulty of connecting to multiple comprehensive transportation hubs.
It is reported that as of now, the civil engineering works of Lines 18 and 22 have been completed by 4% in total, and 10 stations and 4 sections have entered civil construction.