Experimental study on splash erosion resistance of granite residual soil improved by microbially induced carbonate precipitation

Abstract

Granite residual soil (GRS) splash erosion poses a global ecological challenge by destroying the soil structure and accelerating the subsequent erosion. Although the microbially induced carbonate precipitation (MICP) technology has demonstrated the potential ability in soil erosion control, its impact on the splash erosion resistance performance of GRS, particularly the regulatory role of bacterial concentration, remains insufficiently studied. This study addressed the effect of bacterial solution concentration (OD₆₀₀=0.5, 0.75, 1.0) on the splash erosion resistance of GRS treated by MICP, through penetration tests, rainfall splash erosion tests, and scanning microscope tests. Results demonstrated that MICP treatment significantly improves the splash erosion resistance capacity of GRS. Optimal bacterial solution concentration was at OD₆₀₀= 0.75, reducing soil erosion weight by 70.04 %-78.00 % and increasing surface strength by 288 %-513 %. This concentration facilitated the formation of a mechanically stable calcite network, enabling deep mineralization and establishing a gradient-reinforced structure. Conversely, a higher concentration (OD₆₀₀=1.0) induced pore clogging and generated metastable vaterite aggregates, while a lower concentration (OD₆₀₀=0.5) weakened cementation due to insufficient CaCO₃ precipitation. These findings underscore the critical role of bacterial concentration in determining spatial uniformity, crystal morphology, and CaCO₃ content, which collectively govern the effectiveness of the hard crust layers in resisting splash erosion. It was also found that the hydrophobic hard crust layers were generated via pore filling and particle cementation, which dissipates raindrop kinetic energy and protects the uncemented layer. These findings provide direct theoretical and technical guidance for field applications in GRS regions.