Spectral response of blasting vibrations for crown pillar safety in coupled open-pit – underground mining

Abstract

To evaluate blasting vibration spectral response and crown pillar safety under coupled open-pit – underground mining, field monitoring, signal analysis, and numerical simulation were combined at the Shizhuyuan polymetallic mine to investigate spectral characteristics of blasting vibration signals and crown pillar stability. The monitored signals were analyzed in the time, frequency, and time – frequency domains, and the relationship between maximum charge per delay and safe crown pillar thickness was established. Crown pillar stability was analyzed under self-weight stress, most unfavorable load, strength reduction, and blasting dynamic loading. Results show that blasting vibration signals differ from open-pit blasting in dominant vibration stage and frequency-band distribution. Strength reduction analysis indicates progressive instability, with tensile and shear safety factors of 1.7 and 3.4. Under blasting dynamic loading, the 50 m-thick crown pillar remained stable, with a roof-center peak particle velocity of 12.2 cm/s, a maximum vertical displacement of 4.52 mm, and a maximum stress of 0.74 MPa, all returning to initial states after loading, indicating stability. These results can provide a reference for blasting parameter optimization and crown pillar safety control in similar mines.

Keywords

coupled open-pit and underground mining / blasting vibration / spectral characteristics / crown pillar stability / numerical simulation

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