Tunnel boring machines with single-or dual-modes often face challenges adapting to complex geological conditions.Therefore,the mode-selection and-conversion technology for three-mode tunnel boring machines using the Luogang station-Shuixi station section of the Guangzhou metro line 7 as a case study.This project section encompasses soft soil,water-rich sand,and hard rock strata.The tunnel boring machine's geological characteristics,tunneling risk,and mode adaptability are comprehensively examined,providing guidance for mode-selection and-conversion technology for three-mode tunnel boring machines.The results demonstrate the following:(1)The open and hard rock mode is suitable for long hard rock formations with high strength,the slurry balance mode is effective in water-rich sandy strata with high settlement requirement,and the earth pressure balance mode is effective in soft soil layer with boulders.(2)The three-mode tunnel boring machine exhibits adaptability to various geological strata,facilitating functional integration and ease of operation.(3)The mode-conversion capability of the tunnel boring machine is rapid,enabling fast construction.The screw and slurry mucking modes efficiently handle mucking operations and prevent slurry gushing under hard rock and water-rich challenging conditions,respectively.
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