Dynamic Influence of Near-Source Seismic Ground Motion on Underground Mine Working Stability Using Time-Frequency Analysis

Adam Lurka,Grzegorz Mutke,Piotr Małkowski,Sandro Carbonari

doi:10.1155/2021/9023550

Adam Lurka, Grzegorz Mutke + Show 2 more

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https://doi.org/10.1155/2021/9023550

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Abstract

Peak particle velocity parameter is very useful in assessing underground mine working stability. Its application is widespread and requires additional analysis of the dominant frequency of the seismic signal. In order to properly analyze the velocity amplitudes of strong ground motions generated from seismic sources, time-frequency properties of near-source seismic signals in underground mines should be quantified. Using numerical calculations, the continuous wavelet transform (CWT) of the recorded near-source seismic signals in three perpendicular directions was obtained to characterize its time-frequency properties. The properties of recorded strong ground motion velocity seismograms for two high energy seismic events and two blasts from two underground coal mines in Poland have been extracted with the use of continuous wavelet transform spectrograms showing the duration time of each frequency group. Assuming a constant peak particle velocity amplitude on the analyzed seismograms, the duration time of each frequency group starts to play a key role. The longer the duration time of the lower frequency group is on the CWT spectrogram, the more the damaging effect on underground mining excavations can be observed. Varying bandwidths of dominant frequencies in separate time intervals for the analyzed seismic signals have had significantly different influence on the potentially damaging effect on underground mining excavations.

Highlights

Seismic phenomena are commonly encountered during underground mining operations. ey apply to both coal mines and metal or salt ore mines
We have found that nearsource seismic vibrations generated by two high energy seismic tremors and two blasts in Bielszowice and Rydultowy mines in Poland are highly nonstationary stochastic processes
In [24], it was observed that, after blasting, peak particle velocity values (PPV) values can be very high, but they have very high frequency bandwidth with no damaging effect on underground mine workings, even when the PPV values are greater than 1 m/s. e frequency characteristics of the seismic vibrations generated by numerous low energy seismic events appear to be very similar to blasting and are not dangerous for excavation stability

Summary

Introduction

Seismic phenomena are commonly encountered during underground mining operations. ey apply to both coal mines and metal or salt ore mines. Additional dynamic stresses in the rock mass in the area of excavation caused by the seismic shock wave near the source may lead to problems with its maintenance and in the worst cases can completely damage the excavation, leading to injury or death of miners. From the point of view of the damaging effects of the mining excavation, one of the key parameters is the seismic PPV (peak particle velocity) value, which depends on the physical properties of the rock mass and the seismic source itself. In coal mines at distances 200–300 m from the seismic foci, PPV values are usually of the order of a few millimeters per second and do not pose a threat to underground infrastructure [6]. The particle velocity amplitudes always depend on the magnitude and distance to the seismic source

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