预裂缝对爆破振动频谱分布特征的影响

Influence of pre-splitting crack on spectrum distribution characteristics of blasting vibration

预裂孔首先起爆形成贯通预裂缝对随后主爆孔爆破的振动频谱特征和能量分布产生重大影响。依托金沙江白鹤滩水电站左岸坝肩边坡开挖爆破试验,通过对预裂孔爆破和主爆破(主爆孔+缓冲孔)的振动信号进行小波包分析,获得预裂孔爆破和主爆破的功率谱和能量谱。通过对比发现:爆破振动的能量主要集中于40 Hz以内且分布极不均匀,存在多个主振频带。而在同一次爆破试验中,不同测点预裂孔爆破的主振频带比主爆破的主振频带分布更广,主爆破的主振频带集中于低频段,并且主爆破的能量和功率向低频的主振频带集中,反映出预裂孔爆破形成的预裂缝能很好地阻挡主爆破能量的传播,并存在高频滤波效应,频率较高、波长较短的振动应力波被预裂缝过滤,而频率较低、波长较长的应力波能更好地穿透预裂缝。试验结论对揭示预裂缝和对爆破振动传播及其频谱特征变化的影响具有参考价值。

Penetrating presplit cracks induced by presplit blasting have a great influence on spectrum distribution characteristics and energy distribution of the main blast hole ^ s blasting. The excavation blasting tests were conducted at Baihetan hydropower station dam section, s rock high side slope on the left bank side of Jingsha River. Based on the data obtained with the excavation blasting tests, the vibration signals＇ power spectral density and energy spectral density of the main blast hole,s blasting and presplit blasting were gained using the wavelet packet analysis. The results showed that the blasting vibration energy focuses on the range of 0 - 40 Hz, and the energy distribution is extremely uneven ; there are several main vibration frequency bands; the main vibration frequency bands of presplit holes blasting are distributed more widely than those of the main blast holes blasting be at different measured points in one excavation blasting test ; compared with presplit holes blasting, the power spectral density and energy spectral density of the main blast holes blasting are centralized into main vibration frequency bands with lower frequencies; the pre-splitting crack induced by presplit blasting can prevent the energy transmission of the main blasting, and there is an effect of higher frequency filtering; the lower- frequency vibration stress waves with longer wavelength can better pass through pre-splitting cracks.