砂岩单轴压缩破坏全过程声发射主频特征分析

通过单轴压缩声发射实验获得红砂岩受压破坏全过程的声发射低频、高频信号及力学特征,对获得的信号波形采取小波阈值去噪后提取其主频,基于频谱分析理论,分析了砂岩破坏全过程的主频变化特征和频带能量占比规律。研究结果表明:声发射信号主频值分为10~25 kHz、45~60 kHz、120~135 kHz、140~155 kHz、160~175 kHz密集度明显的5个特征频段,其中45~60 kHz的频段对应着岩石试样发生破坏时的主要破坏模式,高于45~60 kHz的频段和低于45~60 kHz的频段分别对应着微小裂纹的萌生和较大裂隙的形成;主频频率变化特征在岩石变形破坏各阶段表现不同,压密至弹性变形阶段内,较为集中,主要存在于特征频段内,进入微裂隙稳定发展阶段后,分布范围由较为集中朝复杂离散方向转变,裂隙扩展至破坏阶段,在更加离散化的同时又相对集中;岩石临近破裂时,声发射信号主频段更加离散化;声发射信号频带能量主要集中在0~250 kHz,其中46.875~62.5 kHz和234.375~250 kHz频带的能量占比随荷载的增加,分别减小与增大。

Analysis on Dominant-frequency Characteristics of Acoustic Emission in Sandstone Uniaxial Compression Failure

Through the uniaxial compression acoustic emission test,the acoustic emission low frequency and high frequency waveform signals of red sandstone compression whole failure process and the mechanical characteristics were obtained.Wavelet threshold denoising was performed on the signal waveform that has been obtained,and then the dominant-frequency of the signal was extracted.Based on the theory of spectrum analysis,the dominant-frequency variation characteristics and the frequency band energy proportion characteristics of the sandstone whole failure process were analyzed.The results show that the dominant-frequency values of acoustic emission signal are divided into 5 obvious dense characteristic frequency bands with 10~25 kHz,45~60 kHz,120~135 kHz,140~155 kHz and 160~175 kHz,in which the frequency bands of 45~60 kHz correspond to the main failure modes of rock specimens.The frequency bands higher than 45~60 kHz correspond to the generation of tiny cracks and lower than 45~60 kHz correspond the formation of large cracks.The characteristics of the dominant-frequency change are different in different stages of rock deformation and failure.From the compaction stage to the elastic deformation stage,the dominant-frequency is relatively concentrated and mainly appears in the internal of feature frequency band.After entering the stage of micro cracks stable development,the distribution range changes from relatively concentrated to complex discrete direction.The cracks extend to the failure stage,and become more discrete and relatively concentrated.When the rocks are near rupture,the dominant-frequency bands of acoustic emission signals become more discrete.The energy of the acoustic emission signal band is mainly concentrated in 0~250 kHz,the 46.875~62.5 kHz frequency band energy ratio decreases with the load increase,and the 234.375~250 kHz frequency band energy ratio increases with the load increase.