Abstract:

When shallow tunneling is carried out underneath existing surface buildings in urban area, the effective control of the blasting vibration plays an important role in ensuring good tunneling efficiency on the premise of having no adverse effect on the existing surface buildings. With a running tunnel of the first phase project (Line 3) of Qingdao Metro crossing underneath a Home Inn as background, rational cut hole types, charging structures and blasting parameters are designed, which brings the vibration velocity of the ground surface under 2.0 cm/s; the blasting network is optimized on basis of millisecond blasting technology and outer hole delaying technology, which reduces the blasting number of an individual driving cycle from 5 times to 2 times and shortens the blasting time by one third. In this way, the blasting technology has achieved good economic and social significance.

Key words: Qingdao Metro, shallow tunnel, tunneling underneath existing building, microvibration blasting technology, network design, milisecond blasting, outerhole delaying