• Explosives and Blasting
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• v.32 no.3
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• pp.18-25
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• 2014

Ground vibration and noise from blasting operation are known to be the most representative constituents which can cause human and material damage. In this study, the effect of delay time on ground vibration is investigated by adopting seven different delay times in bench blasting. For each delay time, three blasting operations were performed. The prediction equations for blasting vibration are derived from 50 sets of measurement and the time theory of Langefors is evoked in the analysis of the blasting vibrations and frequencies. For the delay times of 8 ms and 28 ms, the average values of ground vibration are 5.76 cm/sec and 5.75 cm/sec, respectively, which are considerably low. Also the cyclic variation in the vibration measurements with the delay time confirms the interference effect. From the application of the measurements of blasting vibration and frequency to the time theory of Langefors, it is concluded that the optimum delay times are 8 ms and 24 ms for the test site.

• Tunnel and Underground Space
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• v.20 no.2
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• pp.112-118
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• 2010

Before blasts that can have direct impacts on human bodies or structures, it is necessary to assess impacts of ground vibration. Therefore, frequency has been recognized as an important factor in order to assess impact on ground vibration and damages. There have been many studies on impacts of frequency. But, there have been no studies on relations between vibration and frequency according to delay time difference. In this study, we examined the relations between delay time difference and frequency according to each frequency with which reinforcement and destructive intervention repeat through delay time difference obtained using superposition modeling of single hole blasting waveform based on the theory of time difference developed by Langefors.