Abstract: In order to reveal the dynamic process and change rules of slurry diffusion in split grouting, the foundation bed coefficient method is employed to study the influence of size effect on deformation of different soils in the process of split grouting. The width equation of split crack of different soils is established. The form of slurry diffusion is supposed to be the horizontal radiation circle. The process of split grouting is analyzed based on the stress coupling effect of slurry and soil and the conservation of mass of slurry. Based on the above analysis, the equations for variations of slurry diffusion radius, temporal and spatial variations of slurry pressure and split crack width are obtained. The rules and influence factors of slurry diffusion are investigated. The analysis results show that the slurry diffusion radius continues to grow along with time, but the growth rate continues to reduce. The slurry diffusion radius is positively related to the standard value of foundation bed coefficient and negatively related to the slurry viscosity. The slurry diffusion radius of cohesive soil is smaller than that of sandy soil. The slurry pressure is positively related to the time and the standard value of foundation bed coefficient. At most positions, there is a positive correlation between the slurry pressure and the viscosity. The slurry pressure of cohesive soil is smaller than that of sandy soil. The split crack width continues to grow along with time. At most positions, the split crack width is negatively related to the standard value of foundation bed coefficient and positively related to the slurry viscosity, and the split crack width of cohesive soil is larger than that of sandy soil. Finally the comparative analysis of the calculated and field test values indicates that the difference of calculated and measured results is acceptable. Obviously, the proposed method is of high rationality.