Abstract: To investigate the disaster-inducing mechanisms of internal erosion in levee foundations,a series of experiments was conducted using self-developed equipment. Six groups of specimens with different fines contents were designed,and their internal erosion failure processes were quantitatively analyzed using acoustic emission(AE)and particle image velocimetry(PIV)techniques. This study explored particle movement,acoustic characteristic precursors to failure,and their evolutionary patterns. The results indicate that: (1)PIV effectively captured the entire seepage failure process. The migration velocity of fine particles was highest at the specimen center. The seepage induced internal erosion process was divided into six stages: initial stage,fine particle initiation stage,initial piping stage,piping development stage,piping maturity stage,and seepage failure stage. (2)Fines content is a key factor influencing the seepage process. Specimens with fines content exceeding 15% exhibited greater stability compared to those with 5% and 10% fines content,suggesting that the impact of seepage diminishes as fines content increases. Furthermore,lower fines content leads to an earlier initiation of fine particle migration. (3)The relationship between acoustic emission signals and fine particle velocity distribution prior to seepage failure was revealed. AE energy peaked at the moment of seepage failure,while the b-value showed a declining trend before this peak. This research provides a basis for describing,explaining,and predicting the seepage failure process using AE characteristic parameters.