The research focused on exploring the characteristics of fault stick-slip instability and the combined multi-source precursor characteristics of acoustic emission (AE) and charge signals through bidirectional shear friction experiments on syenogranite with faults of different dip angles under lateral pressures of 5, 15, 25 MPa. The mechanical behavior of the fault and time-frequency characteristics of AE and charge induction signals were observed and analyzed. The key findings and observations are summarized as follows. (1) Lateral pressure and fault dip were found to change the stick-slip characteristics, affecting the induced charge and the magnitude of AE event. Increasing the lateral pressure led to gradual increase in the proportions of induced charge and charge accumulation rate in the meta-instability stage and stick-slip instability stage gradually increase. Compared with 56 degrees fault, the amplitude based statistical index b-value of 45 degrees fault was smaller, and the proportion of large-scale rupture was larger. (2) The fractal dimension of amplitude was observed to reflect differences in energy released by the fault. Phased response characteristics of the frequency characteristics of AE and charge induction signals were identified as effective means to discern the evolution process of fault stick-slip at the laboratory scale. A sharp increase in the main frequency amplitude was recognized as one of the precursor characteristics. The AE and charge induction parameters (energy, fractal dimension and spectral amplitude) in the stage from meta-instability to stick-slip instability showed distinct "sudden increase" characteristics. (3) There was a good correspondence between the energy of AE and charge induction signal and the stress drop, although not entirely synchronous. AE signal responded to stick-slip instability before charge induction. It was emphasized that combining AE and charge induction signal characteristics is essential for achieving mutual complementation and verification of the acoustic-charge binary signal.

To explore the effect of different stress environments on fault-slip rockbursts. Bidirectional shear friction experiments with different lateral pressures were conducted on precracked syenogranites buried at 800 m. The macroscopic statistical parameters (cumulative number of AE events, magnitude and b value ) and local characteristic parameters (amplitude and dominant frequency) of acoustic emission during the stick-slip process under different lateral pressures were investigated. In addition, based on fractal theory, the nonlinear characteristics of AE spectrum were analyzed. On this basis, the microscopic mechanism of fault stick-slip was discussed. The results show that the lateral pressure influences the friction strength of the fault and stick-slip motion characteristics. With increasing lateral pressure, the proportion of transgranular shear fractures increases, which leads to an increase of cumulative number of AE events and magnitude. The periodic decrease in the b value is more significant at high lateral pressure. There is a good correlation between a high-magnitude AE event and a stress drop. The AE frequency with phased response characteristics can be used to effectively identify the evolution of fault stick-slip instability at the laboratory scale. A sharp increase in the amplitude of the dominant frequency can be regarded as one of the precursory features of fault stick-slip instability. The AE frequency spectra have multifractal characteristics, that differ among the different stages. The maximum multifractal dimension and spectral width can reflect the difference in energy released during fault stick-slip motion.

为进一步提高深部地下工程中煤岩失稳破坏监测预警的针对性和准确性,采用自主研发的多通道电荷感应和微震综合监测系统,监测和分析在不等幅循环荷载作用下煤岩变形破裂过程中电荷感应和微震信号的时、频特性和能量特征,并与单轴压缩实验进行对比.结果表明:循环荷载下煤岩在不同阶段的电荷感应和微震信号各具特点,卸载段会产生较多微破裂和损伤,煤样在发生多裂纹贯穿劈裂破坏前会频繁出现峰值较小的电荷感应信号,需特别注意.对微震信号傅里叶变换进行频谱分析,发现微震信号频谱特征能够很好地反映煤样内部裂隙的扩展状态,并且主频幅值的增高与微震信号的增强具有同步性.采用电荷感应和微震信号共同划定煤岩的受载阶段,可以得到更加准确的失稳预警信息.

采用多参量(电荷感应、微震和声发射)同步综合监测系统,开展完整和预制裂纹正长花岗岩的三点弯曲试验,对其变形破裂过程的多参量信号特征进行研究.试验结果表明:完整和预制裂纹正长花岗岩在失稳破坏阶段有最强的多参量信号,在失稳破坏阶段产生的多参量信号的主频比较接近,但完整正长花岗岩多参量信号主频幅值是预制裂纹正长花岗岩多参量信号主频幅值的2倍左右.完整正长花岗岩从线弹性变形阶段、裂纹快速发展阶段到岩石失稳破坏阶段产生应力降时应力降的速度是快速增大的,裂纹快速发展阶段和岩石失稳破坏阶段声发射的最大震级和事件数远大于线弹性变形阶段的最大震级和事件数.正长花岗岩失稳破坏阶段多参量信号同步产生,产生的多参量信号与其他阶段相比主频最小,主频幅值最大;在试样失稳破坏阶段声发射信号早于电荷感应信号产生;电荷感应信号早于微震信号产生,声发射信号持续时间最短,微震信号持续时间最长,多参量信号都在试样产生应力降或失稳前产生.

During the process of rock deformation and failure, a significantly large number of charge signals are generated as a result of fracture appearance and crack expansion. The generation of charge signal is the comprehensive embodiment of the coal-failure behavior. The study of charge signal in the process of fractured-rock deformation and failure is of great significance to the prediction of rock dynamic disasters such as tunnel-engineering stability, slope instability and earthquake. In this work, a surveillance system utilizing charge induction is employed to extract precursory information related to the instability and failure of precracked syenogranite. The results reveal a significant influence of fractures on the strength of syenogranite specimens and the number of charge-induction signal events. The position of the charge signal generated is related to the crack dip angle. Furthermore, with the increase of the crack inclination, the number of events and the amplitude and power value of the charge-induced signal increase and reach the maximum in the instability-failure phase. The syenogranite specimen has a relatively large value, medium correlation, or even high correlation charge-induction signal in the phase of rack propagation, which can make an early warning of the deformation and failure risk of syenogranite; with the increase of the fracture degree, the charge-induction signal with large values and high correlations gradually increases.

The research on charge induction and microseismic characteristics of coal and rock under different loading rates is of great significance for rockburst prediction. In this study, the coal and sandstone samples from the No. 11 mine of Pingdingshan Coal Mine are prepared. The charge induction and microseismic synchronous comprehensive monitoring system is built. The uniaxial compression tests of coal and sandstone samples under the different loading rates are conducted. The charge induction and microseismic signal characteristics in the deformation and fracture process of the coal and rock under the different loading rates are studied. The results show that, with the increase of loading rate, the compressive strength of the coal and rock samples increases and the time from the peak stress to instability failure becomes shorter. At the same loading rate, the softening failure stage time of coal is longer than that of sandstone. With the increase of loading rate, the duration of charge‐induced signal and microseismic signal is longer and the events’ number and amplitude of charge signal and microseismic signal increase in the deformation and fracture process of the coal and rock. Before the instability failure, the charge‐induced signal and microseismic signal have both synchronous and asynchronous signals, and the amplitude of charge‐induced and microseismic signals in each channel is different, which is related to the distance from the position of each sensor to the fracture point of the sample. During the instability failure, the charge induction and microseismic signals of each channel are generated synchronously, and the signal amplitude reaches the maximum values of 50 pC and 6 × 10 −3 m/s at the same time. With the increase of specimen stress, the dominant frequency of microseismic signals first increases and then decreases, while the amplitude of dominant frequency increases synchronously. The dominant frequency amplitude of microseismic signals is the largest in instability failure. With the increase of loading rate, the spectrum amplitude of microseismic signals changes little in the compaction stage, but the spectrum amplitude increases in other stages. At the same loading speed, the events’ number of the microseismic signal of coal samples after peak stress is more than that of sandstone samples, and the signal amplitude is also larger. However, the spectrum distribution range of microseismic signals of coal samples is wider than that of sandstone samples, and the spectrum amplitude of coal samples is lower than that of sandstone. With the increase of loading rate, the time of the first generation of high‐amplitude signals is advanced, and the stress of specimen becomes smaller when the first generation of high‐amplitude signals occurs. With the increase of loading rate, the duration of microseismic and charge signal is longer, and the mean square amplitude of charge signal is larger.