Abstract: Rockburst caused by underground engineering excavation has obvious time-lag effect. Previous research shows that the occurrence of hysteresis rockburst is closely related to the time-lag damage of the rock. Based on this, considering that the surrounding rock is at different stress levels after excavation, the time-delay uniaxial compression test is carried out to analyze the time-delay deformation and failure characteristics of rocks under different stress levels. The results show that the stress level has a significant impact on the time-delay deformation and failure of rocks. As the stress level increases, the failure incubation time decreases exponentially, but it is much longer than that of conventional uniaxial compression failure. In the case of delayed uniaxial compression failure, the hoop strain and volume strain of the rock sample are significantly greater than that of conventional uniaxial compression test, and when the stress level is lower than 90%, the hoop strain at failure rapidly increases and exceeds the axial strain, which is also the distinguishing feature of time-lag failure and conventional uniaxial compression failure. The total energy of delayed uniaxial compression failure is equivalent to that of conventional uniaxial compression, but the proportion of dissipated energy increases significantly in the process of delayed loading, indicating that the delayed loading stage will lead to the significant development of damage in the rock. The rapid growth of circumferential strain of rock samples in the stage of time-delay loading leads to the significant increase of near axial splitting tensile failure cracks, which also leads to the more serious fragmentation of rock samples. The relevant research results can provide a good reference for the analysis and interpretation of time-dependent and time-lag rockburst of rock damage and failure under high stress level.

Key words: time lag, stress level, deformation characteristics, dissipated energy, failure mode