Calculation of equivalent charge weight per delay and vibration velocity prediction for millisecond delay blasting

Drilling and blasting is the most economical rock fracture technology in water conservancy, transportation, mining and tunnel engineering. And the application of nonel detonator network in rock blasting is still the most widely used initiation method in engineering blasting practice. Due to the detonator delay error, there is a deviation between the actual initiation time and designed initiation time in the Nonel detonation network, which will cause the change of blasting time sequence and the overlapping of blast-holes. There are detonator dispersion phenomenon with the same delay time and superposition effect for seismic waves with different delay time, which brings great trouble to the value of charge weight per delay and the prediction of particle peak vibration velocity. In order to the predict particle peak vibration velocity more accurately and efficiently, the millisecond delay blasting test was conducted, and the calculation model of vibration velocity for group blast-hole simultaneous blasting with dispersed charge was established. The influence of the blast-hole number on the equivalent charge weight for simultaneous blasting and its value selection method were studied and constructed. The modified particle peak vibration velocity scaled distance formula and the particle peak vibration velocity prediction method were proposed based on the results of regression analysis of single-hole blasting. The results show that the equivalent charge weight of group blast-hole simultaneous blasting is smaller than the nominal charge weight per delay, and the equivalent charge weight of simultaneous blasting can be calculated by converting through the reduction coefficient, which decreases exponentially with the increase of the blast-hole number. The superposition effect of seismic waves with different delay time can be considered by introducing vibration wave superposition factor into the modified particle peak vibration velocity scaled distance formula. The average absolute error, average relative error and root mean square error between the actual and the predicted particle peak vibration velocity values are 0.05 cm/s, 9.52% and 0.059 cm/s, respectively. It is feasible to apply the modified particle peak vibration velocity proportional distance regression analysis method to the prediction and control of blasting vibration velocity in the field.