【Domestic News】CRTG Achieves Breakthrough of China's First Three-Mode TBM Tunnel
On September 16th 2022, with the successful breakthrough of the right line of Luogang-Shuixi tunnel section of Guangzhou Metro Line 7, Phase II, CRTG accomplished the first two-line three-mode TBM tunnel in China. The Luogang-Shuixi tunnel project extends from Luogang Station all the way to the north along Xiangxue 3rd Road by passing through Huangpu Tram Line 1 and Huangpu District Government Affairs Service Center, and then runs under Yingcui Park Hill, Luogang District Government Building and Academician Building, and finally arrives at Shuixi Station. The right line tunnel is 1086.4m long, with a maximum gradient of - 25.0‰. The tunnel’s overburden is from 20m to 66m. The minimum curve radius of the section line is 600m. Two cross passages are set in the middle. The geology along the right line of Luogang-Shuixi section is upper soft and lower hard stratum, and includes boulder formation and buried weathered deep trough, with complex geology and surrounding environment, which causes great difficulty and high risk to construction.
To ensure safe and smooth tunneling, Guangzhou Metro Group, together with China Railway (Guangzhou) Investment & Development Co., Ltd., China Railway Engineering Equipment Group and CRTG, developed a three-mode TBM, which was first used in the Luogang-Shuixi section, and the safety and tunneling capacity was significantly improved. The average tunneling speed of the three-mode TBM is 5.5 rings per day, with the maximum advancing speed in hard-rock geology section of 13 rings per day. The quality of the formed tunnel is perfect, and there’s no dislocation or leakage during segment assembly.
Common TBMs are mainly single-mode TBMs and dual-mode TBMs. As the name implies, a single-mode TBM can be only a slurry type (direct discharge, air cushion), an earth pressure type, open type or other types. Most of multi-mode TBM are mode combinations of "slurry & earth pressure", "earth pressure & hard-rock", and "slurry & hard-rock". Three-mode TBMs have the slurry mode suitable for geology with large permeability coefficient, sensitive surface, uneven and unproved boulder strata, and the earth pressure mode for geology with highly weathered rock strata and soil layers, as well as the hard-rock mode for full-face hard rock section and developed rock fracture zone. The three modes can be switched easily by operators in the control room based on different strata without entering the cutter-head chamber and thus avoiding risks. In addition to the convenience of switching modes, smooth muck discharge and mud discharging with pipelines are also Three-mode TBMs’ highlights, which can achieve continuous discharge of rock slag and dust-free in working area. It also reduces the abrasion of cutter-head and cutter to a certain extent, and effectively avoid ground safety risks caused by water gushing in open-type TBM tunneling.
East Third Ring Road B 10,
Chaoyang District, Beijing City, P. R. China
No.2 (Self-Made), West Side of Gongye 4th Road,
Guangzhou City, Guangdong Province, P. R. China
Tunnelling to Link the World