The study of compacted deformation and void evolution in broken rock masses is considered highly important for goaf stability control, safe resource extraction, and geological disaster prevention. The broken rock masses from the caved zone of the 10806 fully mechanized mining face in Erhai Coal Mine were taken as the research object. Indoor physical simulation methods were used. Uniaxial compression tests were conducted with different particle size distributions (0~2 cm, 2~4 cm, 4~6 cm, 6~8 cm, 8~10 cm, and mixed gradation). The tests were performed using an electro~hydraulic servo universal testing machine combined with an acoustic emission monitoring system. The compacted deformation characteristics and void evolution laws of the broken rock masses in the caved zone were systematically investigated.The compression process of broken rock masses is divided into a rapid compression stage (loading time < 400 s) and a deceleration stage (400~900 s). In the initial stage, the compression amount is found to account for more than 74% of the total deformation. The void ratio decrease is observed to be 30% to 39%.Particle size distribution is shown to significantly affect compression characteristics. For coarse particles (8~10 cm), due to fewer contact points and lower friction resistance, the compression amount is increased by 34% to 51% compared to fine particles (0~2 cm). The void ratio of the mixed gradation (0~10 cm) is eventually stabilized at 25% due to void filling by fine particles, which was 6% lower than that of the single coarse particle group.It is indicated by acoustic emission monitoring that, except for the 0~2 cm group, the acoustic emission energy of other groups is observed to exhibit a “first increase then decrease” trend. This trend is correlated with particle crushing in the rapid compaction stage and a friction-dominated mechanism in the slow compaction stage.The nonlinear relationship between “particle size-compression amount-void ratio” and the acoustic emission damage evolution mechanism in broken rock masses is revealed by the research results. A theoretical basis is provided for the timing selection of slurry filling in goafs and stability control.