Abstract:
This study was carried out to compare vertical and horizontal bench blast(s) at a
granitic gneiss rock quarry located in Colombo, Sri Lanka and predict the resulting peak particle
velocities of ground vibration levels. To achieve these objectives, particle velocities and frequencies of
38 and 35 blasts respectively were measured in three perpendicular directions for horizontal and
vertical bench blasts respectively with the use of Instantel Blastmate II seismographs. In the blasts,
Ammonium Nitrate (ANFO)(blasting agent) primed by a Gelatine Dynamite primer were electrically
initiated. Scaled distance parameters (Maximum charge weight per delay and distance between
blasting points to monitoring location) were also recorded. The extensively used equation for seismic
low of propagation proposed by Devine (1962) and Devine and Duvall (1963) was used for the
prediction of peak particle velocities. Points were plotted with Peak Particle Velocity (PPV) in Y- axis
against Scaled Distance (D/Q0.5) in X- axis. Regression analysis was performed to define the line of
best fit. At the end of statistical analysis, an empirical relationship with good correlation was
established for prediction of peak particle velocity. Frequency analysis was also done for dominant
frequency and Zero crossing frequency to identify the effect of frequency of ground vibration to
structural damages and defining the most suitable type of frequency analysis to define the single
frequency value for ground vibration. The established relationship, frequency analysis and result
obtained are presented.
