Prediction of the air wave due to blasting inside tunnels: Approximation to a ‘phonometric curve’

Abstract

A review of the results of a previous research, has pointed out that only the magnitude of the blasting air wave at the tunnel portal depends on the tunnel and blasting design parameters (section, length, distance to the portal, maximum charge per delay…). For a given sound level at the tunnel portal, the magnitude of the air wave outside the tunnel depends on the attenuation due to natural or artificial barriers, similar to how a lamp focuses the light more along a given direction than along others. In this work, the air wave propagation outside the tunnel is briefly explained and a phonometric and iso-attenuation curves are proposed in order to represent the phenomenon and to synthesize the solution for a given case. Finally, a charge–distance curve is proposed in order to solve the problem in an easy way.