New Approach for Identification of Suitable Vibration Attenuation Relationship for Underground Blasts
For construction and mining activities, excavation in hard or weathered rock or even hard soil, is often performed with the help of blasting. As a safety practice the blasting operation has to be designed such that the existing structures in the vicinity are not adversely affected due to the blasting activity. Blast vibration attenuation relationship for the ground media becomes necessary for the design of blasting. In India, the relevant IS code specifies an attenuation relationship (Power expression) between the peak particle velocity, the charge weight and the distance of the monitoring point from the blast. However, the empirical coefficients are provided in IS code for only two categories - hard rock and weathered rock / soil. Hence they result in uneconomical and sometimes unviable blasting design. The alternate option is to establish site specific attenuation relationship for the location and use the same for design of blasting operation. Industrial practice is to find the empirical constants for the same Power expression (as IS code) from the site trial blast data.
For this purpose, the same dataset is used for parameter estimation as well as evaluation of the suitability of the estimated parameters. In this study it is demonstrated that evaluation of performance with a different dataset alters the conclusions. Further, expressions other than the commonly adopted Power expression might be more suitable for the relationship. In this article, two other expressions, namely, Reciprocal expression and Weibull model were identified which could be equally good. Exponents for scaled distance calculation, other than the popularly adopted 0.5, were found to be applicable in the case study. Trail blast data from a site was used to demonstrate the same. It was concluded that while developing site specific attenuation relationship, various expressions with different exponents may be examined for their suitability and this should be done with a fresh dataset. The best expression identified for the site should be finally adopted for further activities.