Abstract: When cement-based alkaline materials are extensively utilized in peat foundation soils, the subsurface alkaline environment resulting from alkalization may adversely affect the peat soil, which is critical for evaluating its engineering performance. A systematic experimental study was conducted to investigate these damaging effects by simulating typical engineering alkaline environments (Ca(OH)₂ and cement-hydration systems) and analyzing environmental alkalinity, specimen morphology, compressive strength, solid phase composition, and microstructure. Results indicate that humic acid dissolution constitutes the primary mechanism for soil structural degradation in both alkaline environments. Accompanied by varying degrees of humic acid leaching, specimens exhibited apparent morphological deterioration, significant reduction in strength, continuous loss of solid phase components, pore enlargement with interconnected network formation, and progressive loosening of the soil skeleton. These cumulative effects resulted in severe structural damage to the peat matrix. Furthermore, while Ca²⁺ infiltration occurred in Ca(OH)₂ environments and hydration products accumulated in cement systems，providing partial structural compensation，these beneficial effects were insufficient to offset the alkaline-induced degradation. The structural compensation effect was consistently outweighed by the corrosion and porosity-increasing impacts of the alkaline environments. These findings offer new perspectives for mitigating alkaline damage and enhancing the engineering performance of peat soils in underground construction applications.

Key words: Ca(OH)₂ alkaline environment, cement-hydration alkaline environment, peat soil, soil structural damage, humic acid