群孔齐发爆破岩体振动频谱特性研究

基于理论分析推导出群孔等效爆炸荷载的频域表达式,并代入黏性岩体爆破振动速度幅值谱表达式中,得到群孔齐发爆破激发的岩体振动速度幅值谱表达式。针对露天台阶深孔爆破,以正方形布置的四孔爆破作为研究对象,研究群孔齐发爆破岩体振动频率的影响因素及主频衰减机制。结果表明:群孔齐发起爆激发的振动速度幅值谱随爆心距、炮孔间距、单孔药量的增大,频谱结构由高频向低频偏移,其中随爆心距或炮孔间距的增大,爆破振动主频呈现出明显的衰减,且爆炸荷载的上升时间及下降时间直接影响爆破振动频谱的成分比例。对比三种典型岩石参数条件下的爆破振动主频衰减规律,发现主频与岩体弹性模量及纵波波速成正比,而主频衰减速度与岩体弹性模量及纵波波速成反比,其中锦屏大理岩中爆破激发的振动频率较小,且主频衰减速度最快。

Vibration Spectrum Characteristics of Rock Mass in Simultaneous Borehole Blasting

Based on the theoretical analysis,the frequency domain expression of equivalent blast load of group holes is derived,which is substituted into the expression of amplitude spectrum of blasting vibration velocity in cohesive rock mass.The expression of amplitude spectrum of rock mass vibration velocity excited by simultaneous blasting of group holes is obtained.As to open-pit bench deep hole blasting,four hole blasting with square layout is taken as the research object.The influence factors of rock mass vibration frequency and attenuation mechanism of main frequency are studied.The results show that with the increase of blast center distance,blast hole spacing and single hole charge,the frequency spectrum structure shifts from high frequency to low frequency,at the same time the increase of pitch or blast hole spacing blasting,blasting vibration main frequency attenuation obviously,and the rise time and fall time of explosion load directly influence the proportion of blasting vibration spectrum.Comparing the attenuation law of the main frequency of blasting vibration under three typical rock parameters,it is found that the main frequency is in direct proportion to the elastic modulus of rock mass and the longitudinal wave velocity,while the attenuation speed of the main frequency is inversely proportional to the elastic modulus and longitudinal wave velocity of the rock mass.The vibration frequency excited by blasting in Jinping marble is relatively small,and the main frequency attenuation speed is the fastest.