Objective Thick top coals are common in roadways excavated along the bottom of thick coal seams. Mine earthquakes along the mining face can exert dynamic loading on thick top coals in roadways, prone to induce the dynamic instability of thick top coals and even roof fall-rock burst compound disasters. Therefore, there is an urgent need to explore the mechanisms behind the dynamic instability of thick top coals in roadways under dynamic loading induced by mine earthquakes.

Methods This study investigated a roadway of deep thick top coals in the Binchang mining area, Shaanxi. Specifically, this study analyzed the dynamic instability characteristics of deep thick top coals in the high-stress roadway, investigated the multi-field evolutionary patterns of thick top coals in the roadway under different static/dynamic loading using numerical simulations, and determined the mechanisms behind the mine earthquake-induced dynamic instability of thick top coals in high-stress roadways.

Results and Conclusions  The results indicate that the roof fall zone of thick top coals in the roadway is far from the mining face. Roof falls were followed by the exposure of the flat roof and the breaking of anchor cables in the roof. Concurrently, high-energy mine earthquakes occurred near the roof fall zone, resulting in roof fall-rock burst compound disasters. An increase in static load corresponded to continuously increasing fracture depths and deformations of surrounding rocks in the roadway. As the time and intensity of dynamic loading increased, the vibration velocity, acceleration, and fracture developmental degree of top coals increased gradually, along with significantly increasing detachment layer number of top coals. The anchor bolts and cables for the roof, all located in the fracture zone of top coals, showed significantly reduced support performance. Under the static/dynamic loading, the cumulative damage and detachment layer number of thick top coals in the roadway increase gradually. The dynamic loading induced by high-energy mine earthquakes leads to significantly elevated vibration velocity and acceleration of shallow broken top coals. Consequently, the anchor cables break off when the load acting on them exceeds their bearing capacities, and the shallow broken coals fall at a relatively high speed, thus inducing the dynamic instability of thick top coals and even roof fall-rock burst compound disasters. Based on these results, this study proposes preventing and controlling the dynamic instability of deep thick top coals in roadways by reconstructing the active and passive supports of thick top coals and reinforcing pressure relief.