Compaction and re-crushing characteristics of granules with varying lithologies under multiple mining-induced disturbances

To investigate the compaction and re-crushing characteristics of fractured rock under multiple mining. This study conducted cyclic loading and unloading mechanical tests on aggregates of different lithologies. The variation patterns of mechanical parameters of granules were systematically investigated. The granules energy evolution characteristics and fractal dimension were clarified. The research findings indicate that low-strength mudstone granules exhibit the greatest strain under identical loading conditions, requiring relatively low cumulative energy during compaction. Meanwhile, mudstone shows the highest fractal dimension, indicating the greatest degree of crushing. During the initial loading stage, the granules porosity rapidly decreases, the compressive modulus rises, and the granules is rapidly compacted. When stress exceeds a certain threshold, the compressive modulus continues to decrease, energy density increases significantly, and the granules undergo extensive fracture. The research findings provide significant support for elucidating the compaction and re-crushing mechanisms of granules in caving zones under multiple mining.