Applicability of Microbial Calcification Method for Sandy-Slope Surface Erosion Control

Surface soil erosion is one of the most common slope degradation processes. In this study, microbial calcification (MC), a stimulated natural biocementation process, was investigated for its feasibility as a sandy-slope surface erosion control method. An artificial model slope at 30 degrees was treated by MC via the surface spraying method at three cementation solution concentrations (0.2, 1.0, and 2.0 M). Simulated rainfall was sprayed on the slope surface at 5 mm/min for 30 min. Results show that MC treatment with 0.2- and 1.0-M cementation solution improves surface erosion resistance in terms of observed erosion pattern with time, soil loss weight and rate, and outflow properties. However, MC treatment with 2.0-M cementation solution does not improve surface erosion resistance. Instead, substantial soil loss is observed under rainfall impact while soil is washed away in cemented aggregates. At the end of the rainfall erosion test, microstructural features of the surface samples were identified by scanning electron microscope (SEM) observation. It is found that the effectiveness of MC for sandy-slope surface erosion control is determined by (1) overall CaCO3 precipitation content, (2) treatment depth, and (3) competence between CaCO3 crystal growth and nucleation process.