Abstract:

In the drill and blast construction of the onshore section of Jiaozhou Bay Subsea Tunnel in Qingdao, there are surface buildings only 12m above the tunnel crown. The technology of bottom heading followed by crosssection enlarging is adopted and large parallel cut made by hydraulic rock drilling jumbo and rational drilling and blasting design are used, which brings the maximum vertical vibration velocity of the surface buildings to be within the range allowed by the national standards. Sequence detonation by means of mediumdelay detonators outside the blast hole is used, which achieves once ignition for the bottom heading and the subsequent crosssection enlarging and overcomes the difficulty in the insufficiency of the delays in once large crosssection blasting. Blasting vibration tests and regression analysis are made, which achieves the rules of the transmission of the vibration waves in the ground; the charging quantity is calibrated on basis of the wave transmission rules.

Key words: Jiaozhou Bay undersea tunnel, blasting design, vibration monitoring, parallel cut, regression analysis