分岔隧道过渡段的爆破振动特性研究

Blast vibration characteristics of transition segment of a branch tunnel

由于分岔隧道过渡段具有特殊的受力结构形式,爆破开挖产生的振动极易造成中隔墙和岩体失稳。以六月田分岔隧道过渡段为工程背景,对先行隧道的爆破振动进行实时监测。通过对爆破振动数据进行分析,得出先行隧道不同围岩级别、监测位置的振动波传播规律。运用三维数值模拟软件,对后行隧道爆破振动作用下先行隧道混凝土衬砌的力学特性进行研究。结果表明:连拱段中隔墙迎爆侧的径向振速最大;小净距段中夹岩的振速衰减幅度要小于连拱段中隔墙;爆破振动对先行隧道混凝土衬砌产生的最大拉应力、剪应力分别出现在迎爆侧的拱腰和拱脚;后行隧道混凝土衬砌的最大拉应力和最大振速存在线性关系,通过拟合公式计算得出临界振速,确定了分岔隧道过渡段爆破振动安全控制标准。

Due to a special structure of transition segment of a branch tunnel,its blast induced vibration is easy to cause middle wall and rock body unstable. Taking Liuyuetian Branch Tunnel transition segment as the engineering background,the blast vibration of its early excavated tunnel part was constantly monitored. By analyzing the blast vibration data,the propagation laws of vibration wave of the early excavated tunnel part under the conditions of different surrounding rock grades and different monitoring positions were obtained. The mechanical characteristics of the concrete lining of the early excavated tunnel part were studied under the action of blast vibration of lately excavated tunnel parts with 3-D numerical simulation software. The results showed that the maximum radial vibration velocity appears at the nearblast side of middle wall in multi-archsegment; the attenuation level of vibration velocity of middle inclusion rock in small distance segments is less than that of middle wall in multi-arch segment; the maximum tensile stress and shear one of concrete lining of the early excavated tunnel part produced due to blast vibration occur at haunch and skew back of nearblast side,respectively; the relationship between the maximum tensile stress and the maximum vibration velocity of concrete lining of the lately excavated tunnel part is linear; the critical vibration velocity is obtained with a fitted formula,the safety control standard for blast vibration of transition segment of a branch tunnel is established.