Three Gelatin-Gum Arabic Microcapsule Formulations for Sand Reinforcement: Direct Shear Behavior and Modelling

Microcapsule-based technology offers a potential approach for extending the service life of ground infrastructure. This study manufactured gelatin-gum arabic microcapsules containing tung oil (GGTO), sodium silicate (GGSS), or colloidal silica (GGCS) and evaluated their effects on the direct shear behaviour of silica sand after 3-28 days of curing under normal stresses of 10-100 kPa. A structure degradation direct shear (SD-DS) model was developed to represent strength mobilization, post-peak degradation, and contraction-dilation behaviour. All formulations increased shear strength. At 30 kPa after 28 days, GGTO, GGSS, and GGCS increased peak strength by 220.7%, 106.4%, and 56.7%, respectively, and end-of-shearing strength by 179.3%, 79.3%, and 67.6%. Their peak apparent cohesions were 72.2, 43.0, and 30.3 kPa, compared with 6.11 kPa for clean sand. For each material-curing condition, one parameter set represented the responses at 10-100 kPa. These parameters were then fixed and applied to independent 28-day tests at 150 and 200 kPa. The model captured the overall shear responses and material-dependent trends. The results demonstrate post-release reinforcement and out-of-calibration prediction across normal stress for fixed material-curing conditions. These findings may extend the range of microcapsules applicable to granular soils and provide a practical framework for representing their direct shear behavior.