Abstract:

In order to solve the problem of overbreak/underbreak of surrounding rock of Wawuzhuang StationGuizhoulu Station Section on Qingdao Metro Line No. 1 induced by drilling accuracy of surrounding blasting holes enslaved to grid steel frame of primary support, the controlled blasting technology of long and short blasting holes is introduced; and then the layout scheme of long and short blasting holes is proposed. Meanwhile, the damage zone of surrounding rock and tunnel overbreak/underbreak amount induced by blasting are analyzed and monitored by particle peak vibration method and tunnel crosssection laser detector, respectively. The results show that: (1) The tunnel overbreak/underbreak amount in Grade Ⅳ surrounding rock section can be controlled within 150 mm; and the shotcrete cost per meter can be decreased by RMB 7 182 by adopting long and short blasting holes. (2) The damage zone of surrounding rock induced by controlled blasting technology of long and short holes ranges from 0.29 m to 0.33 m; and the tunnel crown top settlement and clearance convergence are both less than 10 mm. Good economic benefit and construction effect have been achieved.

Key words: subsea tunnel, tunnel forming, controlled blasting technology of long and short blasting holes, overbreak/underbreak, surrounding rock damage, smooth blasting