不同尺寸砂岩破坏全过程声发射主频分析

对直径相同、高径比不同的4组红砂岩试样进行了单轴压缩声发射试验, 获得了各试样的力学基本参数及试验全过程所释放的全部声发射原始波形信号, 在对每个声发射信号逐一去噪的基础上, 通过快速傅里叶变换提取其主频, 联合时频域共同分析尺寸效应对岩石力学性质及声发射信号主频特征的影响。结果表明, 随着高径比增大, 试样的脆性破坏程度明显, 破裂时的延性减弱;红砂岩声发射信号主频分布范围为10~175 kHz, 明显成频段分布;尺寸效应对声发射信号主频的影响主要体现在频段分布的差异上, 30~60 kHz、140~155 kHz和160~175 kHz为各尺寸试样所共有的频段, 其中30~60 kHz频段占比最大, 对应着岩石损伤演化的最主要破坏模式;岩石变形破坏过程中, 主频分布特征朝复杂离散方向持续转化。

Analysis of Dominant Frequency of Acoustic Emission Through the Whole Failure Process of Different size of Sandstone

Four groups of red sandstone samples with the same diameter and different ratio of height to diameter were taken in uniaxial compression tests for studying acoustic emission, and the basic mechanical parameters of each sample and original waveform signals of all acoustic emission released through the whole test were obtained. After each acoustic emission signal was denoised one by one, the dominant frequency is determined by Fast Fourier Transform, and the influence of size effect on rock mechanics and dominant-frequency characteristics of acoustic emission signal was analyzed by combining time-and frequency domain. The results show that with an increase in the ratio of height to diameter, the sample becomes obviously in brittle failure, and its ductility has been weakened. The dominant-frequency distribution of red sandstone acoustic emission signals is within the range of 10~175 kHz, obviously in frequency band. The influence of size effect on the dominant-frequency of acoustic emission signals can be mainly found in the difference in frequency band. 30~60 kHz, 140~155 kHz and 160~175 kHz are the common frequency bands shared by samples of various sizes, among which 30~60 kHz frequency band accounts for the most in the distribution, corresponding to the most important failure mode of rock damage evolution. During the deformation and failure process of rock, the dominant-frequency distribution characteristics continue to transform in complex discrete directions.