Numerical study on instability failure and energy release of composite coal and rock under dynamic disturbance load

Abstract To investigate the instability failure and energy release of composite coal-rock structures under dynamic disturbance loads, a numerical model of a “roof-coal seam-floor” composite block was established using the UDEC simulation software. The model comprehensively considered key influencing factors including the inclination angle of the contact surface, dynamic disturbance load parameters, and horizontal stress levels, with a particular focus on the failure mechanisms, instability characteristics, and energy evolution of inclined coal-rock composites under dynamic disturbance loading. The results demonstrate that, in comparison to static loads, dynamic disturbance loads exacerbate internal damage within the coal-rock mass, increase overall energy dissipation, and accelerate the dissipation rate, thereby playing a decisive role in its failure. As the inclination angle of the contact surface increases, the model becomes increasingly prone to sliding instability along the contact surface, accompanied by an elevated instantaneous crack propagation speed and pronounced stress concentration. An increase in the dynamic load amplitude elevates the peak kinetic energy, peak potential energy, and horizontal displacement, consequently heightening the instantaneous instability risk of the model. Furthermore, as the horizontal stress intensifies, the overall horizontal displacement of the model tends to increase; when horizontal and vertical loads act in concert, the model is highly prone to generating ultra-low friction effects. The findings of this research are anticipated to provide theoretical underpinnings and engineering references for the prediction and prevention of rockburst in deep coal mines under similar geological conditions, offering significant guidance for formulating safe mining plans and effective disaster prevention and control measures.