Mechanical and Engineering Behavior of MICP-Treated Coarse Siliceous Sands

Microbial-induced calcium carbonate precipitation (MICP) technology has been widely used in geotechnical engineering. The undrained and unconsolidated (UU) triaxial tests were conducted in this study to investigate the effect of bio-cementation concentration and treatment times on the mechanical behavior of MICP treated siliceous sands. Test results indicated that the strength of treated specimen is significantly affected by the bio-cementation concentration. The normalized σ′p/σ′p_u increases exponentially with treatment times and produced calcium carbonate. For the same treatment times, the higher the bio-cementation concentration, the larger the produced calcium carbonate and smaller corresponding failure strain. The void ratio and permeability of treated specimens decrease lineally with treatment times increase. The higher the used bio-cementation concentration, the larger the reduction of void ratio and permeability. SEM analysis illustrates that when the bio-cementation concentration is 0.5 mol/L, the crystal form of calcium carbonate is mainly spherical, while the concentrations are 0.7 mol/L and 1.0 mol/L, the crystal form of calcium carbonate is mainly block. This can explain from the perspective that the treatment effect of 0.7 mol/L and 1.0 mol/L bio-cement cementation is better than that of 0.5 mol/L.