Reduction of rainfall infiltration in soil slope using a controllable biocementation method

Reasonable control of rainwater infiltration rate can ensure that soil slope will not fail due to rapid infiltration of rainwater in heavy rainfall, and at the same time, more rainwater can be infiltrated in light rainfall to meet the water demand of animals and plants. In this study, based on microbial-induced calcium carbonate precipitation (MICP) technique, a controllable bio-method for rainfall infiltration of soil slope was proposed. To have a comprehensive understanding the relationship among the rainwater infiltration control capacity, biocement treated soil permeability, slope angle and rainfall intensity, a series of physical modelling experiments of rainfall diversion on slopes with three types of soils and three slope angles were carried out in the presence of various rainfall intensities. Experimental results indicated that the proposed bio-method had the ability of controlling rainwater infiltration in term of varying rounds of biocement spraying treatment. In general, it was found that the rainwater infiltration decreases with the increase in slope angle and rainfall intensity. In the worst case of smallest slope angle (15°) and lightest rainfall intensity (n = 50 mm/h), more than 82.6%, 92.2% and 84.4% of rainwater were prevented from infiltration into the MICP treated natural sand, fine sand and medium sand, respectively, while the untreated soils were not able to prevent the rainwater infiltration at all. The corresponding maximum local uniaxial compressive strength for the MICP treated natural sand, fine sand and medium sand, respectively, were found to be 2.3 MPa, 2.0 MPa, 2.6 MPa, whereas the flexural stresses were 0.46 MPa, 0.33 MPa, 0.67 MPa, which could resist rainfall droplet impact force. Overall, the proposed bio-method showed good rainwater infiltration control capacity and high bearing strength against the impact of heavy rainfalls, suggesting a good potential to mitigate the rainfall-induced landslides.