An attempt to understand the contribution or the electronic detonator to the quality of the production blast. Application to quarrying operations in Belgium (B)

An experimental study has been carried out in the region of Tournai into two limestone quarries: Gaurain-Ramecroix and Milieu to try understand the contribution of the electronic detonator on blasts. This paper will focus on the results obtained on the Gaurain-Ramecroix quarry and will deal only with generated vibrations. We used a constant 10 to 18 ms delay per blast in one or two rows shots. An alternating firing sequence has been implemented to avoid explosive sensibility problems between adjacent holes; the technique led sometimes to delays as low as 7 ms, especially when working into two rows. The site is instrumented with vibration transducers situated at distances ranging from 40 m to about 700 m; the collected signals have been processed to yield peak particle velocities and frequencies. An interpretation of the time history of the signals is also given to try understanding the wave propagation mechanisms with respect to delay and distance.