|
Descripción
|
|
|---|---|
| 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 the laboratory. The geophone cases were mounted in three different ways on a granite slab fixed to a shaker table: 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 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 slab 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. Such values are an estimate of the overall error for the horizontal components (either longitudinal or transversal) in vibration records. From them and the baseline error determined with the sensor directly anchored to the shaker, the measurement error was obtained. Sensor freely placed on the rock does not provide a good contact with the ground and results depend on the weight of the sensor case. Ground motion is amplified by a factor of 1.12 of the rock motion (i.e. a gain around 1.0 dB) at 52.1 Hz for the heavier sensor?s case and at 71.3 Hz for the lighter; they provide, however, negligible errors at frequencies less than 28 and 40 Hz, respectively. For frequencies above the resonant, the ground motion in the horizontal component is strongly damped by the sensor. Anchored sensors monotonically amplify the input velocity in the frequency range considered, but at a lower rate; a transmissibility up to 1.02 (0.17 dB) is obtained in the common frequency range for blasting (frequencies below 100 Hz). Sandbagging encompasses low reproducibility of the sensor response due to variations in the bag positioning, inherent to this fixation method, and also bad performance if the contact surface is small. The slab motion is damped in the sensor response to 0.78 (-2.16 dB) at low and mid frequencies, and is amplified between 1.07 and 1.2 (0.59 and 1.58 dB, respectively) depending on the test, at high frequencies. Errors are also analyzed as function of the input acceleration levels suggested by common field guidelines. Results encourage considering other factors to decide the coupling method. | |
|
Internacional
|
Si |
|
Nombre congreso
|
7th World Conference on Explosives & Blasting |
|
Tipo de participación
|
960 |
|
Lugar del congreso
|
Moscú, Federación Rusa |
|
Revisores
|
Si |
|
ISBN o ISSN
|
978-5-98746-016-0 |
|
DOI
|
|
|
Fecha inicio congreso
|
15/09/2013 |
|
Fecha fin congreso
|
17/09/2013 |
|
Desde la página
|
116 |
|
Hasta la página
|
121 |
|
Título de las actas
|
7th World Conference on Explosives & Blasting |