Research on the performance of polyvinyl alcohol hydrogel solidifying sandy soil

The sandy soil in the active layer of permafrost in the Qinghai-Tibet Plateau is characterized by low bearing capacity and inadequate stability, which poses a considerable threat to the safety of infrastructure in cold regions. This study employed polyvinyl alcohol hydrogel (HBP) as a solidifying agent for treatment. Through laboratory testing and field evaluation methods, the mechanical properties, freeze-thaw cycle resistance in water-saturated conditions, and permeability of the solidified soil were investigated. Combined with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and mercury porosimetry (MIP). The results demonstrate that hydrogel significantly enhances the unconfined compressive strength (UCS) of sandy soil and improves its freeze-thaw resistance of water-rich environment. When the hydrogel content exceeds 8%, the 28-day UCS of the treated soil increases by approximately 80% relative to untreated samples, and the mass change rate is only 4% after experiencing 10 freeze-thaw cycles in water-immersed environment. These improvements are attributed to the formation of strong hydrogen bonds between the hydroxyl groups in hydrogel and the Si-O bonds in the soil, thereby substantially enhancing soil cohesion. Furthermore, the incorporation of hydrogel significantly alters the soil pore structure, reducing the average pore diameter by 57.3% and increasing tortuosity by 47%. A polymeric film with moisture-regulating and energy-dissipating capabilities is formed on the surface of soil particles, thereby enhancing structural stability. Following stabilization, the bearing capacity of the sandy soil is enhanced to 1.59 times that of the native soil, while the permeability coefficient is reduced by an order of magnitude. This research provides a novel and environmentally sustainable approach for improving foundation performance in permafrost regions, providing valuable theoretical insights and practical guidance for preventing and mitigating engineering challenges in permafrost regions.