Shear Strength and Mechanism Analysis of Sodium Polyacrylate-Modified Soft Soil

To investigate the improvement effect of sodium polyacrylate on the shear strength of silty clay, this study explores the curing treatment of silty clay using sodium polyacrylate. Liquid-plastic limit tests and triaxial shear tests were conducted to examine the impact of sodium polyacrylate on the liquid-plastic limits and shear strength of silty clay, as well as to determine the optimal dosage. Additionally, low-field nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) tests were performed to further reveal the micro-mechanism of sodium polyacrylate’s action. The results show that as the sodium polyacrylate content increases, the liquid-plastic limits of silty clay increase significantly. Compared to untreated samples, when the sodium polyacrylate content is 7%, the liquid limit and plastic limit increase by 132.7% and 167.3%, respectively. Meanwhile, the cohesion of the modified samples increases with the sodium polyacrylate content, while the internal friction angle first increases and then decreases. When the sodium polyacrylate content rises from 0% to 7%, the cohesion and internal friction angles of the modified samples increase by 522.9% and 70.6%, respectively. Through comprehensive analysis of the experimental results, it was determined that the optimal dosage of sodium polyacrylate is 5%. Microstructural analysis indicates that sodium polyacrylate interacts with soil particles through hydrogen bonding and ion bridging, filling the pores between particles and encapsulating their surfaces. This improves the pore structure of the soil and enhances the bonding strength between particles. This study provides a theoretical basis for the application of sodium polyacrylate in soft soil improvement.