Enzyme induced carbonate precipitation for soil internal erosion control under water seepage

Seepage induced internal erosion in earth dams, dikes, and their underlying soil strata may cause destruction of earthen structures and flooding of lowland regions. In this study, efforts were made to evaluate the use of the enzyme induced carbonate precipitation (EICP) method for the control of internal erosion under water seepage. Gap-graded soils with 15% fine particles were improved by the EICP method for 1 to 5 passes. In each pass of treatment, 1.5 pore volume treatment liquid containing soybean-derived urease and 0.5 mol/L equimolar urea-calcium chloride was applied to the soil sample. After the EICP improvement, the soil samples underwent seepage erosion of stepwise-increased flow rates. In addition to the EICP-treated soil samples, an untreated soil sample and a soil sample treated by the microbially induced carbonate precipitation (MICP) method were also tested for comparison. The results showed that, in terms of the amount and rate of eroded fine particles, the EICP soil samples had stronger resistance against seepage erosion as compared with the MICP sample and the untreated soil sample. The erosion control effects also improved with treatment passes. The EICP improvement was also effective in reducing the axial deformation of soil. The level of axial deformation was roughly consistent with the amount of fine particles eroded. The calcium carbonate distribution was relatively uniform in the EICP samples compared with the MICP sample. The results presented in the paper show that the EICP method is a promising solution for the control of seepage induced internal erosion in soils.