Prediction and measurements of blast vibrations

Imminent ground vibrations are often an undesirable by-product of blasting. The `peak particle velocity' (PPV) of vibrations is often used as a means of predicting and/or assessing blast-induced damage. The common prediction models for vibration incorporate the quantity of explosive per delay, without giving any consideration to its degree of coupling and/or its distribution in one or more blast holes. Two phases of small scale blasting experiments were conducted on a rock like material called hydro-stone. The tests examined the effects of decoupling and the simultaneous firing of multiple holes on the resulting PPV. It was observed that the PPV decreased with a reduction in coupling ratio, which can be accounted for by incorporating a decay factor into a standard predictory equation. The PPV produced by the simultaneous firing of multiple holes was less than the predicted values. The measured PPV at any single point was found to be less than double the PPV for a single blast hole. When the number of blast holes fired simultaneously exceeds four, the increase in the PPV at any one point was insignificant. This provided a quantitative explanation to the common observation of `minimum damage' produced by the simultaneous firing of perimeter holes in mining operations.