Mechanisms of Rockburst Triggered by Slip and Fracture of Coal-Parting-Coal Structure Discontinuities

The existence of parting in coal can contribute to unstable slip and shear failure, and even rockburst of mining faces and sidewalls. In this work, the rockburst triggered by the slip and fracture of coal-parting-coal structure (CPCS) discontinuities subjected to dynamic stress was visually investigated by numerical simulation, and the stress and displacement as well as the corresponding vibration characteristics surrounding the parting during the rockburst were comprehensively analyzed. Eventually, the rockburst triggering mechanism was summarized. As a field testimony for verifying the numerical results, the 11.20 rockburst in the first parting zone of the 1307 working face of the Zhaolou coal mine (ZCM) was investigated in detail by microseismic (MS) tomography. The following main conclusions were obtained: (1) rockburst may be triggered by the slip and fracture of a CPCS subjected to dynamic stress with a violent ejection of a large number of parting fragments at a high speed. The peak particle velocity (PPV) 10 m/s can be regarded as a critical vibration velocity for rockburst warning; (2) during rockburst, the vibration characteristics of different positions surrounding the parting are closely associated with the coal and rock failure caused by the slip and fracture of the parting; and (3) based on the clustering of many high-energy MS sources in the parting zone combined with a high P-wave velocity, velocity gradient, stress concentration and strain energy, it was fully verified that the 11.20 rockburst was triggered by the slip and fracture of the wedge-shaped parting. Additionally, the sudden and sharp rise of the fault total area (FTA) can be regarded as a precursory sign to warn rockburst. The in situ observations lend credence to the numerical simulations.