Application of strain gauge and geophone based integrated monitoring system in the measurements of the blast induced low-frequency vibrations

Abstract

The paper presents an evaluation of the low-frequency blast-induced vibration and stress records generated by blasting operations in an open-pit mine. Measurements were conducted using an integrated 3-axial geophone and strain-gauge system. The third-octave analysis confirmed the low-frequency characteristic of the vibrations, within a frequency range of approximately 5–13 Hz. Time-domain analysis demonstrated a correlation between blast-induced vibration records and stress records. The energy of the stress and vibration records was determined using the Matching Pursuit algorithm. The analysis results indicated that blast-induced vibration and stress records were consistent not only in the time domain but also structurally; energy peaks in the analyzed records occurred simultaneously, regardless of the blasting area. The dependency between strain and peak particle velocity (PPV) showed a strong linear relationship in the vertical direction, independent of the distance between the housing structure and the vibration source. In contrast, the linear relationship between the longitudinal and transversal directions and calculated stresses was dependent on the distance between the blasting zone and the housing structure. The Response Spectrum analysis confirmed that all blast-induced vibrations were of the low-frequency type. Additionally, the obtained spectra can be considered index spectra for the applied 25 ms time delay.