Destructive Wave Interference in Underground Blasting Utilizing Precise Timing

�Destructive wave interference has been studied in theory for many years. In application however, limited information can be found. Recently, circumstances have enabled a multidisciplinary team to utilize electronic detonators and seismograph analysis to create destructive wave interference in an underground production blasting application. Springfield Underground, located in Springfield, MO, in conjunction with Orica, ETI, White Industrial Seismology, and the University of Missouri – Rolla has shown the ability to use destructive wave interference in underground blasting to reduce ground vibrations directly above. � Springfield Underground is approaching an area in their underground workings where ground vibrations from blasting experienced on the surface are of particular interest. With only eighty feet of cover, Springfield Underground must tunnel directly beneath the Springfield Municipal Water Supply Tanks. Limits for ground vibrations, regardless of frequency, have been set at 2.0 inches per second by consultants retained by Springfield Underground. The current blasting practices at Springfield Underground consist of a traditional V-Cut pattern with conventional pyrotechnic timing in a room of 50 feet wide and 32 feet tall. In order to reduce ground vibrations to an acceptable level, Orica’s i-kon-System of programmable electronic detonators were used in the same pattern and seismic analysis provided an appropriate resonant frequency for the ground between the blasts and the surface. Using this information, the team was able to design a timing sequence that drastically reduced ground vibrations to an acceptable level even at eighty feet to the surface. Through the use of seismic technology and software, as well as precise accurate timing with electronic detonators, Springfield Underground can now proceed with the development of these reserves. � The paper discusses the process by which the reduction in vibration was achieved in practice, as well as a technical explanation of the effects of destructive wave interference and sacrificial holes.