The effects of the topographic bench on ground motion from mining explosions
- Weston Geophysical Corporation (United States)
Understanding the effects of the bench on ground motion can improve the design of cast blasts and achieve improved blast efficiency while remaining below vibration requirements. A new dataset recorded in September 2003 from a coal mine in Arizona has allowed us to examine the excitation of short-period Rayleigh-type surface waves from four simultaneously-detonated explosions in and below a topographic bench of a mine. The explosions were recorded on a network of over 150 seismic sensors, providing an extensive understanding of the ground motion radiation patterns from these explosions. We detonated two separate explosions in the deepest pit of the mine, thus the explosions were shot to solid rock. Within 25 meters of these two explosions, we detonated two additional explosions of similar explosive yields in a bench, thus these explosions were shot to the free face. Radiation patterns and spectral ratios from the explosions show increased amplitudes at azimuths behind the bench relative to the amplitudes in front of the bench. We compared these findings to seismic observations from two {approximately} 1.5 million pound cast blasts at the same mine and found similar radiations patterns. Modeling of these blasts shows that the variations in ground motion are caused by the topographic bench as a result of 1) horizontal spalling of the rock falling into the pit and 2) non-linear scattering near the free-face. Shooting to a buffer also causes the azimuthal variations to be significantly reduced.
- OSTI ID:
- 20674575
- Resource Relation:
- Conference: 31. annual conference on explosives and blasting technique, Orlando, FL (United States), 6-9 Feb 2005; Other Information: IEACR LIB 200; Related Information: In: Proceedings of the thirty-first annual conference on explosives and blasting technique. Volume II, 414 pages.
- Country of Publication:
- United States
- Language:
- English
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