Characteristics of rockburst triggered by weak dynamic disturbance: insights from structural model tests

To investigate how weak dynamic disturbances influence rockburst behavior in deeply buried tunnels, structural model experiments were conducted under true-triaxial compression. Two true-triaxial loading paths were explored. The first path involved no dynamic disturbance, simulating self-initiated rockburst behavior. In the second path, repeated weak dynamic disturbances were introduced alongside incremental increases in static stress, modeling weak dynamic disturbance-triggered (WDD-triggered) rockbursts. The experimental results indicate that WDD-triggered rockbursts exhibit distinct characteristics from self-initiated rockbursts, with these differences significantly influenced by the static stress level at the moment the weak dynamic disturbance is first applied. Compared to self-initiated rockbursts, WDD-triggered rockbursts occur more rapidly and exhibit more violence when the disturbance is initiated at a high static stress of 115 MPa. Conversely, when initiated at a lower static stress of 100 MPa (well below the threshold), WDD-triggered rockbursts progress more slowly and result in milder ejection. Furthermore, WDD-triggered rockbursts lead to a larger fractured band than those caused by self-initiated rockbursts, with the fractured band size increasing when the weak dynamic disturbance is applied under higher static stress conditions. Additionally, the application of weak dynamic disturbances at high static stress levels can induce greater energy release, resulting in a more severe rockburst.