Experimental Investigation and Analysis of Triggering Mechanism for Fault-Slip Bursts of the Tunnel Surrounding Rock with External Disturbance

Shear-slip type rockburst is one of the most common geohazards confronted in deep underground excavations, which can easily occur after external disturbances. Owing to the sudden occurrence and significant damage caused, investigating the mechanism of these shear-slip type disasters is of tremendous significance in ensuring the safety of underground construction projects. In this paper, our attentions are mainly paid to investigate the necessary conditions and critical energy conditions of fault-slip bursts of the tunnel surrounding rock triggered by external disturbances. First, a simplified model for simulating the sliding instability phenomenon occurring in a blocky rock system under external disturbance is established. Next, using a newly developed testing system for the dynamic behaviour of blocky rock masses, a series of experiments to reproduce the sliding instability phenomenon are conducted; the purple sandstone block system is subjected to the combined effect of a vertical impact load and horizontal constant force. The influence of vertical impact energy on the sliding instability is analysed. The experimental results show that the critical energy of the impact load triggering the blocky rock mass slip instability depends on the shear force, and the higher the shear force, the lower is the external disturbance required. Furthermore, a one-dimensional dynamic calculation model is established to develop a better insight regarding the mechanism of the slip instability induced by external disturbances. A dimensionless energy parameter was introduced to quantifiably characterize the critical conditions of different types of fault-slip events. Theoretical analysis and calculations are presented, and the results agree with experimental observations.

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