Wavelet packet analysis of blast vibration signals of freezing shaft model

Blasting vibration signals were studied from the perspective of energy distribution characteristics,with the purpose that blasting vibration hazards can be understood and hazard control method can be developed. The vibration signals of key points on frozen wall were received through the blasting model test of frozen shaft in Meilinmiao mine, China. The gained signals were analyzed by using wavelet db6,then the energy distribution of the signals in different frequency bands was obtained. The effect of height difference and propagation distance on the attenuation law of vibra- tion signal energy were also studied. Besides,the prediction formula of energy was established with dimensional analy- sis,and the correctness of the formula had been verified by the regression analysis of measured data. The results show that:the attenuation of vibration signal energy in high-frequency part is fast,whereas slow in low-frequency part. Blas- ting vibration energy is widely distributed,and the dominant frequency band consists of many sub-bands. With height and propagation distance increasing,the blasting vibration signal energy has a tendency to concentrate in low frequen- cy. Energy value is proportional to the equivalent amount of explosive and inversely proportional to the equivalent dis- tance. This conclusion provides a theoretical basis for the attenuation law of blasting energy and the safety evaluation of blasting vibration for frozen rock stratum in Ordos basin.