Electrochemical grouting with nanosilica sol for soft soil improvement: mechanism of controlled gelation and reinforcement uniformity

Electrochemical grouting with nanosilica sol offers a promising low-disturbance solution for reinforcement of coastal soft soils. This study systematically evaluate the feasibility of electrochemical grouting using nanosilica sol via its gelling regulation, migration behavior, and reinforcement efficacy through a three-stage approach. Single-variable experiments demonstrate that the gelation time and strength are controllable via Na⁺ concentration gradients, particle size and SiO₂ concentration. U-tube electrophoretic tests reveal migration rates of 0.078, 0.0125, and 0.00981 cm²/(min·V) in coarse sand, fine sand, and clay, governed by pore structure and interfacial charge interactions. Electrochemical grouting model experiments show that the nanosilica sol forms a continuous reinforcement zone in the cathode region, increasing the effective reinforcement area increases from 21% to 63%, and reducing the coefficient of variation (CV) in bearing capacity by 50% (to 43.8%) compared to conventioanl CaCl₂-Na₂SiO₃ grouting. The synergistic mechanism of directed migration, gradient-induced gelation, and pore-scale filling effectively overcomes the limitations of conventional grouting techniques, which offten result in the formation of isolated reinforcement zones.