Abstract
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.
Highlights
With the depths and locations for underground engineering having become increasingly challenging, an increasing number of natural or artificial disasters have been observed, such as rockburst and excavation-induced seismicity [1,2,3]
To study the initiation mechanism of shear-slip type disasters occurring in underground openings, a series of experiments were performed to investigate the triggering of the sliding instability phenomenon in blocky rock system
(2) A series of experiments were conducted to reproduce the sliding instability phenomenon in a blocky rock system that was subjected to the combined e ect of a vertical impact load and horizontal static force. e experimental results showed that the critical energy of the impact load triggering the slip instability depended on the level of shear force; the higher the shear force, the lower was the external disturbance required
Summary
With the depths and locations for underground engineering having become increasingly challenging, an increasing number of natural or artificial disasters have been observed, such as rockburst and excavation-induced seismicity [1,2,3] Both of the above geohazards unexpectedly occur during the excavation of deeply buried tunnels and mines, accompanied with a violent and dynamic release of the residual energy of the surrounding rock masses [4, 5]. Efforts have been made to investigate shear-slip incidents caused by sliding along preexisting discontinuities or structural planes [10,11,12,13,14,15,16,17] These advances have improved our understanding of shear-slip incidents, the involvement of a specific feature in dynamic failure as well as development of an effective physical calculation model has not been examined yet. A one-dimensional dynamic calculation model is established for developing better insight into the mechanism of a slip instability induced by external disturbances. e theoretical analysis and calculations are presented, and it is found that the results agree with the experimental observations. e results provide a theoretical reference on the safety of underground tunnel construction
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