Study on the compressive deformation and acoustic emission characteristics of gangue filling materials with different immersion durations

• Subjecting gangue backfill materials to different immersion durations. • Study on acoustic emission characteristics of granular samples under compression with different immersion durations. • Study on macro- and micro-scale compressive deformation characteristics of gangue backfill material at different layers. Directly backfilling goafs with waste gangue can reduce surface pressure and provide synergistic support for overlying rock layers. However, the water-filled environment in goafs weakens the load-bearing capacity of gangue. Under long-term pressure, gangue deformation increases, weakening support for the roof and increasing the risk of instability in overlying rock layers. To investigate the pressure-deformation characteristics of water-soaked gangue backfill materials, a pressure-deformation testing apparatus combined with acoustic emission technology was used to study the macroscopic pressure-induced deformation behavior and acoustic emission characteristics of gangue samples with equal-proportion gradation under different water immersion durations. The results indicate that the pressure-bearing process of gangue samples under different immersion durations is divided into 2 stages: loading and constant load. As immersion time increases, the final strain value of the samples gradually increases, but the growth rate gradually slows down. After immersion, the lateral pressure and vertical stress monitored by sensors completely below the load application surface all increase to varying degrees, and the particle size distribution after the test exhibits consistency. The changes in acoustic emission signals during the loading process can be divided into 3 stages: compaction, crushing and restructuring, and sub-stable. The strength and deformation characteristics of the gangue sample jointly influence the intensity of the acoustic emission signals, and the extent of crush decreases gradually from the top to the bottom of the loading surface during the loading process. The research results provide guidance for the prediction and prevention of ground subsidence in water-filled goafs filled with gangue.