Bio-mediated method for improving surface erosion resistance of clayey soils

Soil surface erosion is a common natural phenomenon, considerably leading to land degeneration and environment deterioration. In this study, microbially induced calcium carbonate precipitation (MICP), a green and sustainable bio-mediated technique to stabilize soils, has been proposed as a promising solution to control surface erosion of the clayey soils. Clayey soil samples with different sand additions (0, 10, 20, 30, 40%, w/w) were used to construct slope models. Five groups of soil slope model samples were treated with MICP by the surface spraying method. Another group of samples treated with deionized water was also prepared for comparison. Subsequently, a series of simulated rainfall erosion tests were conducted on these models for which the dip angle is 45°. Results that include the erosion pattern, the weight and rate of the soil loss, and outflow properties revealed that the MICP treatment is effective for controlling the surface erosion of the clayey soils. The microstructural characteristics of the samples of the treated soils, obtained from the scanning electron microscopy (SEM) indicate that the improvement in the erosion resistance can primally be attributed to the protective dense surface crust, mainly calcium carbonate, that gets formed. This layer is responsible for the enhanced water stability and mechanical strength of the topsoil. It has also been observed that with an increase in the sand content added to the clayey soil, the effectiveness of MICP treatment on controlling soil erosion gets further enhanced due to an increased MICP treatment depth and a more stable soil microstructure.