Study on Freeze-thaw Performance and Micro-mechanism of Canal Foundation Silt Treated by MICP

Freeze-thaw deterioration characteristics of foundation soil is the main cause of canal slopes damages in seasonally frozen areas. Soil treatment is an important means to ensure the safe operation of canal. Based on microbially induced calcium carbonate precipitation (MICP) technique, a series of laboratory tests on treated silt with different concentrations, curing ages and freeze-thaw cycles are conducted. The macro and micro indicators of treated silt, such as volumetric rate, permeability coefficient and porosity, are described and its quantitative relationships are established. The results show that under different concentrations and curing ages, the treatment can reduce the freeze-thaw deformation by 70%, decrease the permeability coefficient by at least one order of magnitude, increase the compressive strength by 220.17%, and improve the shear strength index by 65.50%. As the concentration is 1.00 mol/L and the curing age is 28 days, the treatment effect of silt under freeze-thaw cycles is the most significant. In addition, the calcium carbonate precipitation induced by MICP reshapes the microstructure of silt through a series of processes such as filling, cementation, and encapsulation, which ensures the integrity of silt subjected to freeze-thaw cycles. It is also the main reason for the good engineering properties of treated silt in freeze-thaw environments.