关键词: 钻孔机具;长锚孔;高地应力;软弱破碎围岩;木寨岭公路隧道;

Abstract: The selection of suitable drilling tool for the efficient and stable formation of long anchor holes is crucial for further applying long anchor bolt (cable) support technology in tunnels with soft fractured surrounding rock under high ground stress. Relying on the Muzhailing highway tunnel of Weiyuan-Wudu expressway, the in-situ selection of applicable drilling rigs and the adaptability study of drill bits were carried out. The results showed that: ① YT28 was vastly superior to YG80 in the aspect of drilling efficiency, which demonstrated that in tunnel with soft fractured surrounding rock under high stress, the drilling efficiency of rigs can be effectively improved by increasing the percussion frequency, so the percussion frequency should be considered as the control index. ② The I-shaped drilling bit is superior to the cross-shaped drilling bit in the aspect of drilling efficiency, that the formation time of 5m and 10m holes is 8 minute and 7 minute less respectively, but there was a defect of frequent jamming of the I-shaped drilling bit. ③ In terms of the service life, the average effective drilling length of the cross-shaped was 35m, which was vastly superior to the I-shaped (20m). In terms of hole-forming effect (required pre-tightening force > 300kN), the anchoring success rates for 5m and 10m holes drilled by cross-shaped drilling bit were 98% and 95% respectively, which was significantly better than the holes drilled by I-shaped drilling bit (89% and 75% respectively). The research results can provide guidance and reference for the drilling operations of long anchor holes in tunnels with soft fractured surrounding rock under high ground stress.

Key words: drilling tool; long anchor hole; high ground stress; soft fractured surrounding rock; Muzhailing highway tunnel