Acoustic emission monitoring of dry and water-saturated limestone under uniaxial compression was performed in this research to explore the acoustic emission law under water-rock coupling conditions. Signal analysis method inclusive of fast Fourier transform, short-time Fourier transform, and discrete wavelet transform were adopted to compare and analyze the time domain, frequency domain and time-frequency characteristics of the dry and water-saturated limestone specimens. Results showed that water had a notable influence on the deformation and failure characteristics of limestone. Compared with that in dry state, limestone in water-saturated state had markedly lower uniaxial compressive strength and basic time domain characteristic parameters such as amplitude, energy and ringing count. Before failure, the dry and water-saturated limestones both presented an overall trend of transition from “high main frequency and low amplitude” to “low main frequency and high amplitude”. Before failure, the value of main frequency of dry limestone was higher than that of water-saturated limestone; whereas after complete destruction, the main frequency of dry limestone declined sharply and became lower than that of water-saturated limestone. The main frequency of water-saturated limestone was stable with small fluctuation.
Key words
water-saturated limestone /
dry limestone /
uniaxial compression /
acoustic emission /
signal analysis /
dominant-frequency
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