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Descripción
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| This work investigates the performance of some of the measurement techniques used in vibrations from blasting monitoring. Two tri-axial geophones with cases of different size, shape and mass were tested in a shaker table. The geophone cases were mounted in three different ways on a granite slab fixed to the plate of the shaker: freely placed, sandbagged, and anchored. A known horizontal periodic motion of constant amplitude, and frequency from 16 to 200 Hz, was applied to the slab. Two amplitude levels of 5 and 20 mm/s (0.2 and 0.79 in/s) were applied when the sensors were sandbagged or anchored and only 5 mm/s when no holding force was applied. The transmissibility of vibrations from the rock to the longitudinal geophone as function of the frequency (i.e. ratio of response of the geophone to the slab motion) has been obtained for each measuring condition tested. The transmissibility is considered a composition of the transmissibility of the rock-to-sensor coupling and the transmissibility of the sensor?s mechanics and electronics. The transmissibility of the coupling is obtained normalizing the total transmissibility with the transmissibility of the seismographs, obtained by a suitable test to which a coupling transmissibility of 1 is assigned. Geophone-to-rock coupling is a resonant phenomenon that may alter the amplitude of the measured waveforms by a factor of 1.2 to less than 0.6. The most accurate and precise measurements are obtained with geophones anchored to rock. On the contrary, freely placed or sandbagged sensors are non-predictable planting conditions that lead to high amplification or damping in most of the frequency band analyzed. It is also shown that existing acceleration criteria to select coupling methods do not necessary lead to good quality (accurate and precise) vibration data. | |
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Internacional
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Si |
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Nombre congreso
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Fortieth Annual Conference on Explosives and Blasting Technique |
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Tipo de participación
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960 |
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Lugar del congreso
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Denver (Colorado) |
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Revisores
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Si |
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ISBN o ISSN
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0000000000000 |
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DOI
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Fecha inicio congreso
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09/02/2014 |
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Fecha fin congreso
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12/02/2014 |
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Desde la página
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1 |
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Hasta la página
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11 |
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Título de las actas
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Proceedings of the Fortieth Annual Conference on Explosives and Blasting Technique. El congreso tiene actas sin ISSN ni ISBN |