特大断面隧道钻爆法原位扩挖的爆破振动测试分析

福州市二环路金鸡山隧道原位扩建工程，采用钻爆法施工，通过爆破振动现场测试，重点分析赋存既有临空面的条件下，爆破振速的最大值及其主频的衰减规律。按萨道夫公式基本形式求出最大爆破振速传播与衰减的拟合式，得到Ⅳ级围岩K值明显小于相关规程建议的取值范围，说明既有临空面的存在能显著减小爆破振动效应。对爆破振速时程曲线进行傅立叶分析，认为爆破振动波在周边岩体的传播过程中，其高频成分衰减相当显著。基于此，建议在原位扩挖隧道的爆破施工中，适当减小掏槽眼的装药量，适当增大扩槽眼和辅助眼的装药量，以利用赋存既有临空面的有利条件，提高洞内破岩效率，减小洞外振动效应。

Blasting Vibration Tests for In-situ Expanding Excavation of Large Section Tunnel

Key analysis is performed for maximum blasting vibration and attenuation law of its dominant frequency under existing free face condition by borehole-blasting method and the site blast vibration test of Jinjishan tunnel in-situ expansion project of Fuzhou 2nd Ring Road. The empirical simulation is got by the basic form of Sadaovsk formula for maximum vibration velocity spread and attenuation and it is found that the K value of Level IV surrounding rock is far less than the range suggested by codes, which implies that the existing free face significantly relieves the blasting vibration effect. The Fourier analysis about the time history of blasting vibration shows significant radio-frequency component attenuation during the spread of the blasting vibration wave in peripheral rock body. Based on these results, it is recommended to suitably decrease the charge weight in cutting holes and properly increase the charge weight in expansion holes and auxiliary holes during the blasting for the in-situ tunnel expanding excavation so as to use the advantage condition of existing free face, improve the rock-breaking effect inside tunnel and decrease the vibration effect outside tunnel.