引松供水工程4标段隧洞主要采用敞开式TBM进行施工，为节省工期，部分洞段变更为钻爆法施工接应，TBM步进通过。为使TBM在圆形钻爆段快速步进，通过分析TBM在圆形断面空推步进的影响因素，研究钻爆段弧形底板的施工方法、质量控制措施，以及TBM在步进过程出现撑靴撑不到洞壁、撑碎洞壁，底板破碎和底部高低不平等问题的解决措施，使TBM安全、快速步进通过；通过与滑板式步进技术进行对比分析，总结2种步进方式的适应性以及优缺点。

The tunnel in Bid Section No. 4 of Songhua River Water Diversion Project is mainly constructed by open TBM. The drilling and blasting construction is adopted to some tunnel sections to save construction time, where the TBM passes through without load. In order to guarantee the rapid and safe stepping of TBM in the circular drilling and blasting section, the influence factors are analyzed, and the construction methods and quality control measures of arc bottom plate of drilling and blasting section, as well as the solutions to the problems of TBM during stepping process, such as gripper can not support the cave wall or breaks the cave wall, floor breaking and uneven bottom height, are studied. The adaptability, advantages and disadvantages of two kinds of stepping methods are summarized by comparative analysis with slidingtype stepping technology.