To explore the potential precursors of rock instability, it is necessary to clarify the mechanism of micro-crack from fracturing to failure, which involves the evolution of fracture size, orientation, source model, and their relationships to the loading. The waveforms of acoustic emission (AE) recorded by the sensor network attached rock sample during laboratory tests provide a data basis for solving these problems, since these observations are directly related to the characteristics of the fracturing sources. Firstly, we investigated the source mechanism, looking at the rise angle and the average frequency (RA-AF) trends during five loading stages in a uniaxial compression test. Results show that the proportion of shear events significantly increases when approaching instability. Secondly, we calculated the moment tensor for each event, considering the uncertainties of P-wave polarity, azimuth, and the takeoff angles of the rays. Moment tensor solutions suggest that there are obviously more crack events than shear events in all loading stages. Moment tensor evolutions confirmed that the decreasing of isotropic component and the increment of double-couple can be used as precursors of rock fracturing development. Considering the limitations of these two methods, it is suggested that we should be concerned more about the proportions of individual failure components and their evolutions over time, instead of absolutely classifying the events into a certain source type.

Both chemical corrosion and axial compression impose critical influences on the internal microstructure of rock. Meanwhile, chemical corrosion can change a rock’s mineral composition, which in turn affects the physical and mechanical properties of the rock. To investigate the dynamic strength characteristics of white sandstone under the coupling effect of axial load and chemical corrosion, a dynamic and static combined loading test device was adopted for performing cyclic impact tests on white sandstone immersed in chemical solution. The results show that with the increasing number of cycles under the same load, the peak strength of the rock presented a trend of ‘strengthening first and then weakening’. The strength of rock resistance to impact failure reached its maximum when the solution of pH was 7 and axial pressure was 12.6 MPa. Under the same axial pressure, the effect of solution pH on the initial dynamic strength of white sandstone is a normal distribution. Acidic and alkaline environments are harmful to rocks during the initial impact, while neutral environments exert little effect and the pH of the solution influences the particle size of impact crushing particles. In addition, the chemical solution has a significant effect on the deterioration of rock strength during the process of initial impact, and the effect is inconspicuous in the later period.