地铁隧道毫秒延时爆破环境振动特性研究

Characteristics of environmental vibration induced by millisecond-delay blasting in metro tunnel excavation

基于地铁隧道毫秒延时爆破环境振动特性现场试验,考虑爆破荷载的不规则特性,采用基于非对称加卸载准则的修正Davidenkov本构模型描述场地土体的动力非线性特性;通过改进Friedlander方程来模拟内源爆炸在圆柱形炮孔表面产生的瞬态空气冲击波;实现了包含毫秒延时爆破荷载输入和有限元-无限元耦合边界的地层-爆源体系三维精细化有限元模型,并与现场实测数据对比验证了该模型方法的有效性。对50 ms延时爆破和齐爆引起的环境振动特性进行了数值模拟,对比发现毫秒延时爆破不仅可以有效降低地表峰值振速,而且可以显著改变地表振动的频谱特性。毫秒延时爆破产生的地表振动频带较集中,对分散爆破振动能量的作用显著,且地表速度响应的主频较高,远离建筑结构自振频率,可显著降低爆破施工引起的邻近建筑物的结构振动水平。

Based on the field test of environmental vibration characteristics of subway tunnel millisecond delay blasting,considering the irregular characteristics of blasting load,a modified Davidenkov constitutive model based on asymmetric loading and unloading criterion is used to describe the dynamic nonlinear characteristics of the site soil.The transient air shock wave generated by the internal explosion on the surface of cylindrical blast hole is simulated by improving the Friedlander equation.And a three-dimensional refined finite element model of ground-blast-source system,involving the blast wave input and finite/infinite element coupling boundary,is realized.The effectiveness of the model method is verified by comparing with in-situ testing data.The environmental vibration features induced by 50 ms delay blasting and instantaneous blasting are numerically simulated.It is found that millisecond delay blasting can not only effectively reduce the surface peak vibration velocity,but also significantly change the frequency spectrum characteristics of surface vibration.The frequency band of surface vibration produced by millisecond delay blasting is relatively concentrated,which has a significant effect on dispersing blasting vibration energy.Moreover,the main frequency of surface velocity response is higher,which is far away from the natural frequency of building structure,it can significantly reduce the structural vibration level of adjacent buildings caused by blasting construction.The research results reveal the vibration characteristics and vibration reduction mechanism of millisecond delay blasting environment,which can provide scientific basis and reference for blasting construction of subway tunnel in complex urban environment.