Recently, the composite TBM "Flame No. 7", jointly remanufactured by CRCHI and China Railway 20th Bureau Group, was successfully launched and began tunneling in the Zhuyuancun Station–Chongqing East Station section of Phase I of Chongqing Rail Transit Line 24.

After remanufacturing, the "Flame No. 7" composite TBM has an excavation diameter of 6.86 meters, a total length of 82 meters, and an installed power of 1,750 kilowatts. It is the first composite TBM in China's urban rail transit industry to be used in ultra-large-gradient construction, with a maximum construction gradient of 43‰.

Launch of the "Flame No. 7" composite TBM

The Phase I Lot 1 project of Chongqing Rail Transit Line 24 is located in Banan District and the Economic and Technological Development Zone of Chongqing, comprising three stations and three sections: Lujiaobei Station, Kuangjiatang Station, Zhuyuancun Station, the Lujiaobei Station–Kuangjiatang Station section, the Kuangjiatang Station–Zhuyuancun Station section, and the Zhuyuancun Station–Chongqing East Station section, with a total line length of approximately 5.4 kilometers. The Zhuyuancun Station–Chongqing East Station section, where the "Flame No. 7" was launched for tunneling, has a tunnel length of approximately 2.5 kilometers; the main geology of the section consists of miscellaneous fill, sandy mudstone, and sandstone. The tunnel crown is buried at a depth of 71.7–72.95 meters and follows a "V"-shaped slope, passing through a 500-meter horizontal curve, with a maximum gradient of 43‰. It features ultra-large-gradient tunneling with curves and uneven soft and hard strata, making shield construction highly difficult.

In response to the engineering characteristics of the project, CRCHI, together with China Railway 20th Bureau Group, overcame numerous equipment technical difficulties. To better control the equipment's tunneling attitude and enable it to adapt to large-gradient curves and tunneling in uneven soft and hard strata, CRCHI carried out a series of adaptive modifications and upgrades to the "Flame No. 7" composite TBM, effectively reducing the risks of shield construction.

Construction site of the "Flame No. 7" composite TBM

Upon completion, the project will effectively enhance the north-south transport capacity of Chongqing Rail Transit, expand the辐射 range of Chongqing East Station, provide convenience for citizens' travel, and create prerequisites for building future industrial clusters.