为寻求岩石临界破坏判据和前兆特征,在花岗岩单轴压缩声发射试验的基础上,获得了岩石变形破裂全过程中的声发射时频域信号信息,结合频谱分析理论提取了波形信号的主频值,将时频域各特征参数联合起来,共同分析其变化特征及破裂前兆识别信息。研究结果表明:声发射事件率在高应力阶段之前,表现为以高、低值交替出现,到高应力阶段后,以中、高值交替出现;累积事件数表现为随荷载的增加快速上升,在极高应力时突然转为平缓;能率及累积能量随岩石加载过程可分为2段“活跃期”和1段“缓慢释放期”;主频分为1^#—5^#的5个频段,其中2^#频段对应岩石破裂过程中最主要的破裂模式,3^#,4^#,5^#频段属于高频段,1^#频段属于低频段,高、低频段分别对应微小裂纹的萌生和微小裂纹闭合形成大裂隙;声发射时频域各参数均有较好的前兆识别特征,破裂前兆时间响应顺序为:主频最早,事件率、能率及累积能量次之,累积事件数最晚。研究成果可为声发射技术运用于实际岩土工程中监测预防煤岩复合动力灾害发生提供可靠依据。

In the aim of obtaining the criteria and precursor characteristics of critical rock fracture, uniaxial compression acoustic emission experiment was performed on granite to acquire the time and frequency domain signal information of acoustic emission during the whole process of rock deformation and rupture. According to the spectrum analysis theory, the dominant-frequency value of the waveform signal was extracted, and the parameters of time and frequency domain are combined to analyze the variation features and the identification information of rupture precursors. Results unveiled that the acoustic emission event rate alternated between high and low values before the high-stress stage, and between high and medium values after the high-stress stage; the cumulative number of events climbed rapidly with increasing load, but suddenly tended to be gentle at very high stresses. The energy rate and cumulative energy can be divided into two active periods and one slowly releasing period with the loading process. The dominant-frequency can be divided into five frequency bands of 1^#-5^#, therein the 2^# frequency band corresponded to the main rupture mode of rock’s rupture process, the 3^#, 4^#, 5^# frequency bands belonged to the high frequency band, and the 1^# frequency band belongs to the low frequency band, with the high and low frequency bands respectively corresponding to the initiation of microcracks and the formation of large cracks by microcrack closure. The parameters of time-frequency domain in the acoustic emission are of good precursor recognition characteristics. The time response sequence of rupture precursor follows the order of dominant-frequency, event rate, energy rate and cumulative energy, and then cumulative number of events.