小间距隧道爆破动力特性试验研究

Experimental study of blasting dynamic vibration of closely adjacent tunnels

分岔隧道是一种新型隧道结构形式。以漆树槽分岔隧道为工程背景,进行了掘进爆破的围岩震动效应试验,通过不同掏槽结构下爆破震动作用隧道围岩衬砌质点振动速度的频谱分析与质点振动速度幅值的分布情况分析,对小间距公路隧道混凝土衬砌及其围岩在爆破地震波作用下的力学特征进行论述,重点研究了小间距隧道中隔墙及爆破掌子面的震动特性及变化规律。试验与分析结果表明,(1)中墙迎爆侧为振速峰值区,以水平径向振速最大,且沿着中墙走向呈现规律性变化;(2)掏槽孔爆破产生的地震效应最为强烈,其震动强度是扩槽眼和周边眼的2倍左右;(3)衬砌振速主振频率主要分布在低频段,以20～95Hz为集中频段,高频地震波衰减极快;(4)同一测试断面中最大振速峰值出现在拱顶和边墙中部位置的概率最大,且大小比较接近,爆破掌子面附近的振速不适合萨道夫斯基预测公式,受爆破夹制及自由面的影响较大。

Bifurcation tunnel is one of the new types tunnels. Taking the project of Qishucao bifurcation as the background, the field experiments of vibration effects of rock masses in tunneling blasting have been done. Based on the measurement of waveforms of the vibration velocity in different distances away from the tunneling blasting sources in the working face of adjacent tunnel, blasting vibration analysis of concrete lining tunnel is described by analyzing the peak particle velocity and its main frequency, especially for the blasting dynamic characteristics of mid-board and its vibration velocity variation. The results of the tests and analysis show that： （1） the near-blast side of old tunnel is the strongest vibration zone and the radial vibration is the highest which has a regular varying character along the mid-board; （2） the seismic effect of cutting hole blasting is the most intensive and its intensity is about two times greater than that of the other two blast-holes blasting; （3） the main vibration frequency of concrete lining is mostly low frequency from 20 Hz to 95 Hz, the higher frequency is absorbed quickly. （4） the peak vibration velocity always appears at the vault or in the middle of the mid-board in the same testing cross-section of the old tunnel; the Sadoy＇s formula is not reasonable for the vibration prediction of particle vibration near the blasting face. In light of construction characteristics of the adjacent blasting, the control measures of blasting vibration are proposed; the presented research achievements have better applied to practical project; and satisfactory results are obtained.