China Railway Engineering Equipment Group Co., Ltd. (CREG) held a ceremony for the EPB TBM named Qianjin (CREC 773) on July 15 at its facility in Zhengzhou, China. The TBM, developed for Karst geological features of Guiyang City, will be the first TBM used in the Guiyang Metro Project.
The Guiyang city project will be challenging due to the complex hydrogeological conditions combined with sedimentary rocks, dissolved limestone, shale, sandstone and many faults. Because of this, dill-blast was used for previous projects.
CREC773 (Qianjin) is 90 m long with a 6.47-m excavation diameter. In consideration of the geological conditions of the project, the cutterhead is designed with opening ratio of 32%, of which 38% is at the center, and the opening is evenly distributed, which is favorable for muck flowing.
The center disc cutters, adopting disc cutter inserted with flat pick which greatly improve the toughness of the cutter, are installed in the way similar to hard rock TBM. It adopts 8 sets of 1,260 kw hydraulic-driven motors, rated torque 6,000 kN·m, and breakout torque 7,200 kN·m. The minimum inclination belt conveyor in China is adopted, which not only improves the reliability of the screw conveyor, but also facilitates the muck removal.
In addition, in the wear-resistant design for the cutter head, the wear-resistant alloy blocks are installed in the ring beam of the cutterhead, which greatly improves the wear resistance of the cutterhead. In the wear-resistant design for the screw conveyor, the wear-resistant composite steel plate is adapted in the casing of the screw conveyor. The screw shaft flights are designed with high manganese block wear-resistant materials. It is also equipped with various counter measures for water burst, advanced geological prediction and probe drilling to effectively prevent construction risks.