爆破震动信号法判别岩体软弱夹层及其厚度的试验研究

在南宁市郊区一试验场地进行了爆破震动信号判别软弱夹层试验,在试验中采用了无线网络控制的爆破震动信号测量系统,并针对以前试验中的不足,改变了药包起爆顺序和改进了监测点布置方式。试验结果表明:在软弱夹层上方爆破的震动信号时域曲线比较规整简单,频域曲线主峰非常突出明显且高频部分很少;在软弱夹层处及其下方爆破的震动信号时域曲线相对软弱层上方要复杂的多,频域曲线叠加了较多的高频成分,曲线中呈现多峰特性,因此根据爆破震动信号的变化规律可判别软弱夹层是否存在。提出采用应力波初至时刻来计算缓倾斜或水平软弱夹层厚度的简便方法,并进行了试验,试验结果表明软弱夹层厚度是近似均匀分布的。

Experimental Study on Identification of Rock Mass Soft Interlayer and Its Thickness by Blasting Vibration Signals

The experiment for identification of soft interlayer by blasting vibration signals were did in an experimental site of Nanning suburb. In the experiment, the blasting vibration signal measurement system controlled by wireless network was used, and the order of dynamite explosion and arrangement of monitoring points were improved to  overcome the shortcomings of previous experiments. The experimental results show that (1) under the condition that blasting area is above soft interlayer, the time domain curves of vibration signals are very simple, the peaks of frequency domain curves are very obvious and high frequency components are few; (2) under the condition that blasting area is in or below soft interlayer, the time domain curves of vibration signals are complex than the case that blasting area is above soft interlayer, the increase of more high frequency components in the frequency domain curves are obvious, and curves show multi-peak characteristics. So the soft interlayer can be identified by the variation of blasting vibration signals. The simple method for calculating the thickness of gently inclined or horizontal soft interlayer by using the initial arriving time of stress wave was brought forward, and the relative experimental result shows that the thickness of soft interlayer is similar to uniform distribution.