灰岩单轴压缩过程中干燥与饱水状态对声发射特征的影响

为探究水岩耦合条件下的声发射规律,通过开展干燥与饱水灰岩单轴压缩条件下的声发射监测试验,并结合快速傅里叶变换、短时傅里叶变换与离散小波变换这3种常用的声发射信号分析方法,对比分析了干燥与饱水灰岩的时域参数、频率特征与典型破裂信号的时频特征。结果表明:水对于岩石的变形破坏特征影响显著,相对于干燥状态,饱水试样的单轴抗压强度下降明显,且幅值、能量以及振铃计数等基本时域特征参数均呈现出大幅降低的特点;岩样破坏前,干燥与饱水灰岩都表现出由“高主频、低幅值”向“低主频、高幅值”过渡的总体变化趋势;干燥岩样破坏前主频值高于饱水岩样,完全破坏后却低于饱水岩样,主频下降幅度大,而饱水岩样的主频值波动较小,频率较为稳定。研究结果对于工程尺度的防突机构声发射监测具有一定的参考价值。

Acoustic Emission Characteristics in Dry and Water-saturated Limestones under Uniaxial Compression

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.