Preserving the microstructural fabric integrity of sand: A non-invasive gelatin-based hydrogel stabilization method

Studying the microstructure of granular materials is crucial for understanding their mechanical properties, such as the fabric in sand piles and deep-sea soils, but their susceptibility to disturbance during sampling gravely enlarges the difficulty to progression. Existing stabilization methods mainly focus on enhancing soil strength, but fail to preserve the original granular fabric, which is essential for accurate microstructural analysis. This study proposes a non-invasive stabilization method based on gelatin hydrogel, aiming to enhance the self-stability of sand while preserving its in-situ microstructure. Through vibration and consolidated undrained (CU) triaxial tests, this study systematically evaluated the effects of gelatin hydrogel concentrations ranging from 0.25 % to 1.0 % on sand stabilization at the macro scale. The results showed that the 0.5 % hydrogel-stabilized sand exhibited a volumetric strain of only 0.87 % after vibration, demonstrating significant improvement in self-stability. The shear strength of the stabilized sand was similar to untreated sand, with peak deviatoric stress of 192 kPa compared to 191 kPa, and the internal friction angle remained at 28°, indicating minimal alteration to the load-bearing structure at the macro scale. Further non-destructive microstructural analysis using CT scans and environmental scanning electron microscopy (ESEM) confirmed that the hydrogel uniformly filled pores with a 99.12 % filling rate, without altering the particle morphology or the contact network. These findings demonstrate that 0.5 % gelatin hydrogel effectively enhances the self-stability of sand while maintaining its undisturbed internal fabric, thereby providing a reliable and non-invasive approach for microstructural characterization and offering new insight into the flexible cementation mechanism of hydrogel-stabilized sands.