Rainfall-Induced Erosion of Biocemented Graded Slopes

Microbially induced calcite precipitation (MICP), a newly green method, was investigated as a possible solution to rainfall-induced erosion of sandy slopes. A series of model slopes prepared with sands of different gradations were treated by MICP using the surface spraying method. The slopes were subjected to scour under artificial rainfall with an intensity of 700 mm/h. The internal soil loss, the surficial soil loss, the volumes of the internal flow and the surficial flow, and the gradation of the residual soil in the slope model were measured as indicators of the erosion characteristics of the slopes. The results showed that the untreated sandy slopes with a larger uniformity coefficient can be eroded easily while almost no erosion occurred in the untreated ones with a low uniformity coefficient. After MICP treatment, the internal erosion was effectively mitigated for slopes with both large and small uniformity coefficients. In terms of surficial erosion, it was alleviated for the slopes with a larger uniformity coefficient, while intensified for those with low uniformity coefficient, despite the impermeable crusts formed on the slope surface. Therefore, caution must be taken when applying MICP for erosion control of slopes.