Mechanical properties enhancement and permeability control of silty soils by modified sodium alginate

Silty soils exhibit poor engineering properties, including low strength and instability, jeopardizing the stability of geotechnical systems. In this study, a novel soil stabilization approach using a ternary interpenetrating polymer network (IPN) formed through the synergistic reaction of sodium alginate (SA), acrylamide (AM), and hexadecyl methacrylate (HMA) is introduced, which utilizes hydrophobic association and ionic crosslinking to create a strong gel matrix that effectively binds soil particles. A three-factor, three-level orthogonal design was used to optimize the component ratios (SA:AM:HMA). Using SA as a control, a dry-wet cycle test was conducted to compare changes in the unconfined compressive strength (UCS) of SA-treated and SA-modified polymer-treated soils. The results indicate that after 28-day curing, the soil treated with the optimal mixture (1.5:1.5:2.5) could reach the UCS of 2405.69 kPa. Compared to untreated soil, the cohesion significantly increased to 119.66 kPa, whereas the internal friction angle remained almost unchanged. The hydraulic conductivity was reduced to 3.45 × 10^-6 cm/s. The durability of SA-modified polymer-stabilized soil was found to be significantly better than that of SA. Microstructural analyses further confirmed that the polymer gel enhances soil-polymer interaction through pore-filling and chemisorption, considerably improving the pore structure and mechanical properties. This study provides a theoretical basis for applying this novel biopolymer-based stabilizer in silty soil improvement.