Theoretical and experimental investigation of sliding instability in blocky rock system triggered by external disturbance

Based on the structural hierarchy theory, rock masses can be considered as a blocky rock system capable of storing various kinds of a large amount of energy. As the development and utilization of underground space has extended to thousands of meters, the increasingly frequent rockbursts pose a great danger to the constructors and equipment at the construction field. According to its mechanism, rockburst can be broadly divided into strain failure type caused by rock volume damage and sliding failure type caused by fault-slip event. This paper focused on investigating the triggering mechanism of sliding type rockbursts induced by external disturbance. With the simplified theoretical model of contact slipping between rock masses under the condition of initial stress, a non-dimensional impact energy parameter I was derived to quantify the critical conditions of different types of sliding failure events along structural plane. Then the necessary conditions for the occurrence of fault-slip rock burst were derived: Firstly, the contact surfaces of the rock block are in the quasi-stable state with the high initial stress in the tangential direction; secondly, the impact energy factor which characterizes the movement of the rock mass reaches a critical value under the dynamic disturbance. To verify the theoretical result, a series of sliding tests were carried out for purple sandstone blocky system under various horizontal pulls and vertical impact loadings. Both the irreversible displacement and sustained sliding instability are observed, and the critical energy conditions of above-mentioned phenomenon are obtained, which are consistent with the theoretical model. Furthermore, numerical modeling calculations considering rock mass vibration and the slip rate weakening mode of rock friction were performed to better understand the mechanism of sliding instability caused by external disturbances. These results provide a theoretical reference on the safety of underground tunnel construction.