New possibilities of reducing blasting vibrations with an improved prognosis

The standard charge weight scaling laws consider the distance and the maximum charge per delay interval as the only technological factors influencing the peak particle velocity (PPV). Practical experience, however, indicates that drilling- and blasting technology significantly contribute to the PPV. For that reason an attempt is made to improve the prognosis by including a well-known empirical evaluation procedure generally used for the quantification of the specific blasting effect. A correlation between these parameters was derived on the basis of numerous large hole blastings carried out under normal working conditions. Then the vibration immission of the blasts was statistically evaluated under consideration of the measurement site and the comparability of the conditions. The result of this analysis allows the following three fundamental conclusions: 1. Vibrations can significantly be reduced by improving the ignition frequency, and by optimising the delay interval and the ignition in the bore hole bottom. Doing this, various secondary conditions must be taken into account and technological parameters have to be adapted to the meet the specific requirements of the location. 2. Ground vibrations can be minimised by optimising primarily geometrical parameters such as the burden, the spacing and the diameter of the bore holes. By including the effect of specific blasting, the maximum charge per delay interval and the distance r from the blast to a given monitoring location, an improved prognosis can be obtained through the equation PPV = k·L b S ·S ±C g ·r −m 3. Systematic measurement of the dynamic characteristics at each geophone location may contribute towards an improved interpretation of peak particle velocities (PPV) particularly when there is considerable scatter among the PPV data. These dynamic characteristic are measured in the form of the substitutional figure E vd (dynamic elastic modulus) by means of dynamic drop plates.