<p>Underground coal mining causes surface subsidence, which is particularly severe under thick alluvium. Investigating the dynamic temporal process of surface subsidence in thick alluvium areas is crucial for safeguarding surface structures and facilitating ecological restoration. This study analyzes the mechanisms governing mining-induced dynamic surface subsidence and aquifer dewatering-consolidation to accurately describe the dynamic surface subsidence process under thick alluvium. Corresponding prediction methods for each mechanism were established, and a comprehensive prediction model for dynamic surface subsidence in deep thick alluvium was formulated by superimposing subsidence value contributions from both mechanisms at identical time points, explicitly incorporating aquifer consolidation effects. The research findings indicate that surface subsidence progresses through three distinct phases: the first stage is the strata movement-dominated stage (fractures not reaching the aquifer); the second stage is the combined aquifer dewatering-consolidation and strata movement stage (fractures extending into the aquifer); the third stage is the surface subsidence stabilization stage (consolidation completed). Simulation experiments investigating thick alluvial confined aquifer subsidence under varying consolidation conditions, such as differing water contents, thicknesses, and burial depths, have elucidated the fundamental mechanisms underlying dewatering-induced consolidation, revealing characteristic patterns of dynamic subsidence and water inflow. Validation against field monitoring data from the Panel 14022 of Zhaogu No. 2 Mine showed RMSEs of 0.174 m, 0.141 m, and 0.255 m when compared with predicted values, with corresponding RRMSEs of 6.3%, 3.08%, and 5.4%, demonstrating the model’s reliability in predicting surface subsidence. The findings provide a reference for predicting dynamic surface subsidence under analogous geological conditions.</p>