Abstract: The seepage of sandy foundation would lead to the collapse of foundation and the destruction of engineering structure. A series of large-scale sand column seepage model experiments war carried out by microorganism-bentonite combined mineralization method. The discussion in-depth was conducted for the effects of sand particle size, slurry liquid-solid ratio and treatment cycles on the permeability, internal erosion characteristic and bentonite and calcium carbonate precipitation distribution of sand. Moreover, the stability of sealing and the microstructure were thoroughly investigated and the treatment effect of microorganism-bentonite combined mineralization method was evaluated. It was found that this method could improve the seepage prevention effect and the stability of sealing of sand, and the permeability coefficient of samples could be reduced by up to 4 orders of magnitude. In addition, the erosion rate during the permeation process was also reduced by several times and reached as low as 0.51 g/(s·m²). Based on the effect of bentonite and calcium carbonate precipitation on sand sealing, the anti-seepage mechanism of microorganism-bentonite combined mineralization method was analyzed. The results show that the microorganism-bentonite combined mineralization method is feasible and efficient in the seepage control of sand, which will provide an important reference for the application of microbial mineralization technology to engineering anti-seepage problems.

Key words: microbially induced calcium carbonate precipitation, bentonite, permeability coefficient, particle size, slurry liquid-solid ratio