Abstract: Wet tailings dams frequently introduce mineral processing wastewater with varying acidity and alkalinity during discharge. Under prolonged immersion conditions, tailings particles undergo significant physicochemical changes that may further impact the safety and stability of the tailings dam. This study investigated the physical and mechanical properties of typical iron tailings materials （tailings silt, tailings sand, and tailings clay） subjected to long-term immersion in chemical solutions of varying pH levels. It conducted a microscopic analysis of particle morphology changes under acidic and alkaline solutions and explored the influence patterns of acidic and alkaline solutions on the macroscopic physical and mechanical properties of tailings. Results indicate that the porosity of tailings materials decreases with increasing consolidation pressure, with the most pronounced reduction occurring between 0 kPa and 50 kPa. Concurrently, porosity initially increases and then decreases with rising pH. Long-term immersion causes particle size reduction （i.e., increased silt and clay content）, with acid environments exhibiting more pronounced refinement. SEM analysis reveals that acidic immersion results in finer particles with reduced angularity, while alkaline immersion forms cemented agglomerates. As the content of fine-grained tailings increases, cohesion gradually increases while the internal friction angle decreases. Both acidic and alkaline solutions enhance cohesion, but prolonged immersion in alkaline solutions significantly reduces the internal friction angle. This study demonstrates that prolonged immersion in chemical solutions of varying pH alters the microstructure and macroscopic mechanical properties of tailings, providing a valuable reference for assessing the long-term stability of tailings dams.