Source Scaling of Single Fired Mining Explosions with Different Confinement and Explosive Size at a Copper Mine in Arizona 3

Source Scaling of Single Fired Mining Explosions with Different Confinement and Explosive Size at a Copper Mine in Arizona 3 A series of single-fired (simultaneously detonated) explosions were conducted in an Arizona copper mine as part of the Source Phenomenology Experiment (SPE) using IRIS PASSCAL seismometers. The explosions spanned yields from 773 to 6181 kg and were all detonated in an approximate 100 m by 100 m area. In order to quantify the effect of the mine free-face, the individual explosions were also detonated under three different emplacement conditions including at the free-face of the mine under normal burden, twice normal burden and fully contained. The purposes of these experiments were to investigate the generation of regional phases such as Pg, Pn, and Lg from mining explosions, quantify the relationship between yield and seismic amplitudes, quantify the effect of confinement and contrast single-fired waveforms with those from delay-fired explosions. Instrumentation was deployed in the near-source region (100-500 m), local (1-33km) and regional distances. Empirical scaling relations for the different shots in this test series were developed in order to quantify the effects of yield and confinement.

Empirical source scaling relations using the close-in (100-500 m), in mine (1-3 km), local (1-33 km) and regional data are compared for the three confinements. In all cases data at each range document similar scaling. The fully contained scaling (twice depth) quantifies the change in individual source corner as well as absolute source size.
The Mueller-Murphy source model has been used to quantify effects of explosion depth and material in which the explosion is detonated. Material properties were measured for the porphory granite at the mine and used in forward models for the yield scaling of the fully contained explosions. The forward model of the source scaling is compared to the empirical scaling in the figure to the right illustrating the ability to appropriately account for source corder and relative sizes of the absolute energy coupled into the ground.

Typical mining explosions are detonated at a free face or boundary to the pit in order to fail the rock and possibly cast material. Explosions were conducted at the free face in order to quantify energy lost relative to a fully contained explosion. The empirical scaling relations suggest that the free face explosion can experience a factor of 2-4 reduction in amplitude.

Work at SMU on this project was sponsored by the National Nuclear Security Administration Office of Nonproliferation Research and Engineering Office of Defense Nuclear Nonproliferation. Equipment for the study was supplied by the PASSCAL Instrumentation Center.


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