地铁下穿既有铁路桥的爆破动力响应分析

The Dynamic Effect Analysis of the Blasting to the Existing Structures in Subway Tunnel

以大连地铁2号线208标马湾区间浅埋暗挖隧道下穿魏台桥特殊地段为研究对象,通过三维有限元程序仿真模拟以及工程现场动态监测对比,研究爆破振动对既有构筑物的动力响应问题。研究结果表明:爆破地震波振动速度峰值在距爆源较近区域的衰减速度远大于爆源远区,同时沿深度方向的衰减速度大于水平方向;爆破地震波在构筑物中会出现两次或多次峰值振速,说明爆破冲击波具有强烈的多次反射性,对结构的破坏性也较大;不同深度处的监测点其振速达到峰值的时间和峰值大小均不同,越靠近爆源,受扰动的峰值越大,时间越短;近距离爆破会对既有隧道衬砌安全性产生很大影响,在既有隧道衬砌迎爆侧拱腰部位为薄弱区。

The research on the shallow depth excavation tunnel which is under crossed Wei bridge of line 2,208 bid section of Dalian metro was carried out to analyze the vibration response to the structures including lining,bridge and pier,the wave propagation law,and attenuation characteristics in formation by three dimensional finite elementto prevent the blasting construction of stratum and the surrounding both structures caused by excessive deformation and damage.The results show thatthe vibration velocity of the attenuation rate of blasting seismic wave peak is greater than the critical source areaclose to the blasting area,and the attenuation rate is greater than the horizontal direction along the depth direction.The peak velocity of theblasting seismic wave will appear twice or more times in the structure,indicating the blasting shock wave has strong multiple reflection and are destructive to the structure.Displayed in thedifferent depth of fixed-point monitoring,the velocity reached peak at different time and different size.The closer the monitoring point is to the source,the greater disturbing and the shorter time of the peak has.Close blasting will have a great influence of the safety of existing tunnel lining.The blasting side of the arch waist receives the most vibration velocity and needs to be focusedforprotection in site construction.