Rock burst mechanisms induced by dynamic and static loading under composite key strata: a case study

In the Ordos mining area of China, composite effects between adjacent thick and weak sandstone strata increase the risk of rock burst. Understanding the mechanism of rock bursts under these conditions and developing targeted prevention and control measures are prerequisites for ensuring mine safety. This study theoretically analyzed the formation conditions of composite key strata and revealed the mechanism of rock bursts, through the variations of the roof characteristics and dynamic responses in different drilling control areas of the 3^{- 1}402 working face. Numerical simulations were conducted to investigate the influence of thickness ratios and intercalation thickness on composite effects. The results indicate that the formation conditions of the composite key strata require synchronous movement of the key strata, with no shear slip at the contact surface of strata and the maximum shear stress position of the model. Both the peak and range of the advance abutment stress increase, accompanied by intense dynamic load release, which is consistent with field data, supporting the conclusion that rock bursts induced by the composite key strata effect are triggered by the superposition of high static loads and strong dynamic loads. Furthermore, the closer the thickness of the upper and lower strata, and the thinner the intercalation, the more obvious the composite effect between the key strata. The optimized prevention and control schemes effectively reduce the risk of rock burst under composite key strata effects.