Abstract: The application of microbial-induced calcite precipitation (MICP) technology in the soil is mainly affected by the factors: the effective particle size, pore diameter, particle gradation, and hydrodynamic parameters of the particles. The complex pore structure of the soil is difficult to be determined by a single parameter in practical engineering, whereas most of them can be reflected comprehensively by the permeability of the soil. The conditional judgment formulas are proposed for the saturated osmotic grouting with the constant capacity, the step-by-step and low-speed process in this paper. Moreover, with the premise of the size compatibility between the microorganism and the soil particle, the formulas are suitable for MICP method in the soil characterised by the permeability coefficient. Furthermore, the formulas are verified by conducting solidification test, permeability test and strength test on nine types of soil (control particle size 0.040-0.913 mm, initial porosity 31.5%-54.9%) including sand, silt, sandy-clayey purple soil and expansive soil. In the condition of the appropriate value of the permeability reduction parameter ( for cohesionless soil, for cohesive soil), it is showed that the third permeability condition can be applied to all types soil in the tests. In addition, the first permeability condition is more suitable for sandy soil than others in MICP technology. Meanwhile, the formulas of the total volume of grouting solution and the total grouting time are obtained, which provide references for the feasibility assessment of the MICP method and further promotion of this technology.

Key words: permeability coefficient, MICP, applicability, soil matrix, solidification parameters