深部地层地应力水平与爆破振动频率特征的相关性

Effect of crustal stress level on frequency characteristics of blasting vibration

不同的地应力水平对深部岩体爆破振动的频率和能量分布具有重要影响。通过对不同地应力水平的深埋隧洞爆破开挖过程中实测围岩振动信号进行快速傅里叶变换,采用功率谱分析方法研究振动信号在不同频带上的能量分布。研究表明,实测爆破振动的低频振动(<50 Hz)能量占总振动能量的百分比随应力水平的提高而增加;爆破振动在其频域中除了有一个主振频率外,还存在多个子频带,且各子频带振动的能量与主频带振动能量的差距随应力水平的提高而减小;伴随爆破破岩过程而发生的应变能瞬态释放效应诱发围岩振动的主频一般比爆炸荷载诱发振动的主频低;在50 MPa或更高应力水平下,应变能释放诱发的振动能量与爆炸荷载诱发振动能量大致相当。

Different stress level has important influence on the frequency and energy dist ribut ion of blast ing vibrat ion of deep rock mass. Based on the Fast Fourier transform of the measured vibration signals of surrounding rock during blasting excavation of deep buried tunnel under different stress conditions, the energy distribution of the vibration signals in different frequency bands is studied by means of the power spectrum analysis method. The research shows that the percentage of the measured blasting vibration of low frequency vibration energy in total vibration energy would increase with the increase of the stress level. In addition to a dominant frequency of blasting vibration, there are a number of sub bands in the frequency domain, and the gap between the vibration energy of each sub band and the vibration energy of dominant frequency would decrease with the increase of stress level. Accompanied by the breaking process of rock blasting, the dominant frequency of the vibration of surrounding rock induced by the transient release of strain energy is generally lower than the frequency of vibration induced by blast load. At 50 MPa or higher stress levels, the strain energy release induced vibration energy is roughly equivalent to that of blast load induced vibration energy. This research has certain guiding significance to the safety control of blasting vibration in underground engineering.