Mechanism of creep-induced rock burst in extra-thick coal seam under high ground stress

A number of creep-induced rock bursts suggest that this type of rock burst belongs to hidden disasters featuring spontaneity and time delay. Lacking knowledge of its mechanism leads to challenging rock burst prevention and control, posing a severe threat to deep mining safety of extra-thick coal seam. Creep-induced rock burst is closely related to unstable creep. By establishing a creep model and a three-dimensional creep equation, it is found that high ground stress and extra-thick coal seam provide favorable conditions for its formation. The breaking process of roadway surrounding rock due to unstable creep is studied, and it is found that unstable creep activates rock burst and reduces resistance through strength corrosion and stress relief, thus inducing rock burst in weak areas of roadway by the impact of external static stress. An estimation formula for assessing possibility of creep-induced rock bursts is proposed. Based on the mechanism of creep-induced rock bursts, some specific measures of prevention and control are put forward: optimization of roadway layout, strengthening of active support, optimization of pressure relief parameters and long-term stress monitoring.