Vibration monitoring and analysis of the 40 kg TNT equivalent blast containment chamber

In the present work, the vibration velocities of the ground, roof and top of the 40 kg TNT equivalent blast containment chamber resulting respectively from 15, 20, 25 and 40 kg TNT explosion were monitored using velocity sensors and geophones. The measured results showed that all of the ground velocity peaks were less than 5 cm/s, the vibration frequency was almost higher than 10 Hz and the vibration duration reached 5 to 10 s, and the vertical vibration peak of the roof was obviously enlarged by 6 to 7 times that of the horizontal ones. The wavelet packet analysis of the velocities' signal showed that the vertical vibration energy of the ground was 2.5 to 4.0 times that of the horizontal vibration energy, more than 95% of the vibration energy mostly concentrated in the range of 0-160 Hz, while more than 90% of the vertical vibration energy was limited in the range of 10-40 Hz. The results reveal that the attenuation effect of the vibration-isolating trench at a depth of 6 m on the blast seismic waves is imperfect, the independent base and seismic isolation bearing should be adopted if we hope to obtain an ideal attenuation effect especially when the explosive weight exceeds 5 kg TNT equivalent.