On May 6, CREC 820, the first three-mode TBM integrating slurry, earth pressure and hard rock TBMs in China, is successfully launched in the section from Luogang to Shuixi of Guangzhou Metro Line 7 Phase II project. 

The section from Luogang to Shuixi in Phase II Project of Guangzhou Metro Line 7 is 1086 meters long, and the buried depth is about 19-73 meters. It is densely distributed with full section hard rock stratum, soft soil layer and upper soft lower hard stratum. The hard rock stratum to be crossed by TBM is about 800 meters long, with average rock strength of 90 MPa and boulder proved rate up to 66.7%. For a safe and efficient tunneling in complex geological conditions, China Railway Engineering Equipment Group Co., Ltd. affiliated to CRHIC has creatively designed and manufactured a three-mode TBM that integrates slurry, earth pressure and TBM modes. 

The three modes of the three-mode TBM allows for one key conversion depending on different strata. The technicians can operate in the main control room without entering the equipment to disassemble components, averting the risk brought by the long time mechanical mode conversion operation. Moreover, the smooth slag removal mode guarantees stepless and continuous discharge of the slag and no dust in the working area. To a certain extent, this may reduce the wear of cutter head and tools, and effectively avoid the surface safety risk caused by sudden water inrush and failure to close the earth chamber during open excavation.