Development and Characterization of Engineering Superhydrophobic Silica Sol for Enhanced Subsurface Stability and Seepage Control

This investigation employed polydimethylsiloxane (PMHS) for the surface modification of silica sol, preparing a novel grouting material with superhydrophobic properties. Subsequently, testing and microscopic characterization of the superhydrophobic silica sol and the sand-grouting bodies were conducted. Statistical analysis methodologies were utilized to examine the impacts of silica concentration, coagulant content, and pH on the injectability and stability of silica sol, hydrophobicity of silica gel, and the hydrophobicity and strength of the sand-grouting bodies. The efficacy of superhydrophobic modified silica sol was corroborated through microscopic characterization. The results demonstrated the successful grafting of PMHS onto silica surfaces via Si-O-Si bonds, leading to a reduction in surface energy of silica and an increase in its microroughness, resulting in the conversion from hydrophilic to superhydrophobic properties. The stability of superhydrophobic silica sol was enhanced with minimal impact on injectability. The strength of the sand-grouting bodies decreased by up to 50%, while the contact angle reached 154°, and the sliding angle decreased to 7°. As a novel grouting material, the modification of silica sol with PMHS not only effectively mitigates adverse environmental impacts, but also simplifies the modification process and achieving significantly enhanced performance, making it well-suited for extensive implementation in impermeability engineering grouting. For instance, this material can be utilized to reinforce the surrounding soil of tunnels, enhancing soil strength while effectively mitigating the adverse effects of groundwater on tunnel structures.