Blast wave characteristics and its influence with distance of measurement
Extraction of locked-up coal pillars by opencast method and the presence of dwellings in proximity to excavation area lead to specialised drilling and blasting plan for safety of structures and humans. Introduction of improper bench layout, mismatched drilling equipment and blast geometry enhances discomfort for local inhabitants. Blast-induced vibration magnitude also shows poor attenuation rate to cause unwanted impact on structures. Reviewing into the nature of wave signature and characteristics of attenuation for different depth of blast holes and type of explosive, the paper puts forward a theoretical analysis to substantiate the anomaly in vibration monitored at different heights of structure for both opencast and underground blasting operation. In opencast operation, for close distance measurement, reduction in vibration magnitude was observed with an increase in height of measurement. Similarly, when the radial distance between structure and blasting source was more than vertical cover for underground blasting, amplification in vibration magnitude was observed with an increase in height of measurement. Lastly, the paper communicates that vibration should be measured on structures and characteristics of vibration along with different forms of energy transmitted to structure should be evaluated to limit vibration magnitude for safety of structures.
Keywords: blast-induced vibration, component magnitudes, structural safety, triggering component, distance, attenuation, amplification, opencast blasting, underground blasting, opencast mining, underground mining