Review of soil solidification methods in scour and erosion control

This review focuses on the mechanisms and scour resistance of various soil solidification methods used in civil and coastal engineering. Traditional chemical methods, such as ordinary Portland cement (OPC) and lime, enhance scour resistance primarily through pozzolanic reactions and cementitious bonding, which increase cohesion and shear strength. The laboratory results revealed that OPC-solidified soil can resist flows of up to 4 m/s after one day of curing, whereas lime-treated soils can withstand flows of up to 8.5 m/s after 14 days. Polymer-based treatments work by forming a surface-binding network that improves soil aggregate stability; optimal dosages can reduce rainfall-induced erosion rates to as low as 0.3 % compared with those of untreated soil, although their limited strength restricts their use to nonhydrodynamic environments. Ionic soil stabilizers (ISSs), a class of chemical agents, function by replacing exchangeable ions in clay minerals, leading to reduced plasticity, improved particle alignment, and increased soil density. While widely applied in subgrades and slope stabilization, their application in hydraulic environments is still in its infancy. Current evidence of scour resistance remains limited because of insufficient laboratory and field data. Biological methods, including microbial and enzyme-induced calcium carbonate precipitation (MICP/EICP), function by precipitating calcium carbonate that binds particles and fills pores; these methods can reduce sand erosion by up to 80 %–98 %, although the cost and nonuniform distribution of enzymes present challenges. Combined methods leverage complementary mechanisms—for example, carbonate precipitation and cement hydration—to improve microstructure and strength synergistically, with reported increases in critical shear stress up to 971.6 Pa. This review provides a comparative analysis of the methods, focusing primarily on their underlying mechanisms and ability to enhance scour resistance, with additional discussion on costs, environmental impact, and operational complexity. Future research is needed to address how these methods could be optimized for better performance and cost efficiency, especially for large-scale prototype applications.