Abstract: It is of great theoretical and practical significance to study the mechanical characteristics and laws of fault-slip process for predicting the occurrence of fault rockburst. The test material is a kind of coarse-grained syenogranite, the characteristics of stick-slip instability in different fault dip are studied by biaxial loading method. The effects of loading rates of 0.5, 1 and 5 μm/s on the stick-slip instability of faults are studied under different lateral pressures. The results show that: The stress drop during the fault stick-slip instability decreases with the increase of loading speed. The critical shear stress during the fault stick-slip instability is the largest under a low loading speed and a high confining pressure, and the stress drop is the largest when the fault stick-slip occurs. The critical shear stress, the average stress drop and the average period of stick-slip increase when confining pressure increases. With loading rate decreases, average stress drop and average stick-slip period increase under the same confining pressure, and the influence of confining pressure on the average stick-slip period is more significant. The relationship between stick-slip period and loading speed is negative logarithmic linear, and it is not affected by lateral pressure. When the fault dip changes from 56º to 45º, the critical shear stress and the average stick-slip period increase, the average stress drop decreases under the same confining pressure. Fault dip has a significant influence on the stick-slip characteristics of faults. When the fault dip is 34º, the instantaneous instability of the fault occurs when the specimen stress reaches the peak stress, and the energy release increases with the increase of confining pressure. Mining speed has a direct impact on the occurrence of fault rockburst. Under a certain mining speed, fault rockburst is most likely to occur, and the released energy is also large, so the mining speed must be avoided in production.

Key words: fault rockburst, stick-slip, loading rate, fault dip, stress drop