Enzyme-induced calcium carbonate precipitation (EICP) is a soil solidification and improvement technique with broad prospects. In order to study the mechanical fracture mechanism and meso-properties of EICP stabilized sand, this paper, based on PFC2D, studies the mechanical parameters, particle displacement and microcrack development process of cemented sand samples with different cementation levels and different calcium carbonate distributions in uniaxial compression tests to explain their deformation and failure mechanisms and failure evolution laws. The results indicate that discrete element simulation considering the content, distribution, and particle contact model of calcium carbonate can better reflect the mechanical and deformation characteristics of the cemented sand specimens compared with laboratory tests. Specimens with a low level of cementation undergo local shear failure, and the failure surface emerges in areas with lower calcium carbonate content in the middle. With an increase in cementation level, average particle displacement in sandy soil becomes smaller, and the direction of particle displacement is closer to the axial compression direction of the specimen, leading to splitting failure with better global stability. The higher the level of cementation is, the more uniform the distribution of particle contacts in specimens is observed, resulting in slower extension rates for both crack growth and zones experiencing cementation failure.

By setting up six groups of specimens and using the rainfall test, the resistance of modified silt slopes to rain erosion was analyzed through the changes in the surface erosion condition of specimens with respect to the amount of erosion, surface strength and calcium carbonate content. The results show that after spraying the enzyme induced carbonate precipitation (EICP) solution on the surface for EICP and lignin joint-modified samples, the surface integrity is better, the strength and calcium carbonate content are higher, the quality loss is smaller, and the resistance to rain erosion is improved obviously. As results, the erosion amount of the slope soil is reduced by 75.0% on average compared with other specimens, the surface strength is increased by 33.8% on average, and the calcium carbonate content is increased by 235.2% on average. The slope surface sprayed with EICP solution can form a hard shell layer that effectively avoids the erosion of the slope surface, while lignin can provide nucleation sites for the calcium carbonate. Therefore, the distribution of scattered calcium carbonate attaches to lignin, so that the addition of lignin improves the calcium carbonate content and the surface strength also increases with the increase of calcium carbonate content.