Spectral Analysis of Blast Vibrations from Large Explosions
Spectral analysis was performed on 3-component vibration records for 91 large blasts in four different lithologies (taconite, hematite, hard limestone, soft limestone) to characterize the properties of radiating elastic waves. Maximum particle velocity data show considerable scatter but the spectral maxima are consistently below 10.0 Hz over the distance range 300–2000 m. Signal durations are longer for hematite, and soft limestone than for taconite, and hard limestone with the longer signals being characterized by “narrower” frequency spectra. The corner frequency of corrected amplitude spectra varies inversely with source duration, that is, long duration blasts, in agreement with observations for far field earthquake waves. Powder factors for hard rock are higher than for soft rock because of the large taconite and hard limestone are higher than hematite and soft limestone. It was not possible to obtain a definitive relationship between maximum particle velocity and the powder factor because of the larger number of variables in these blasts.
Measurements contained in this study are significant because of the scarcity of published data pertaining to large blasts.
KeywordsGround Motion Amplitude Spectrum Delay Interval Corner Frequency Explosive Charge
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