Abstract: The method of soft soil subgrade reinforcement with chemical churning pile is used more and more in projects of subgrade treatment. At present, the researches about chemical churning pile usually focus on improvement in construction techniques or bearing characteristics of single pile. But research about bearing characteristics of chemical churning pile groups is not much. Based on MIDAS-GTS three-dimensional finite element analysis, the influence of design parameters on bearing characteristics of chemical churning pile groups is studied. These design parameters of chemical churning pile include layout, elastic modulus, length, diameter of piles, and distance between piles, the parameters of interface between piles and soil. The results show that the vertical settlement of soil within the range between surface and pile bottom is reduced in soft soil subgrade reinforced by chemical churning piles; but the method has little effect on the vertical settlement of soil under pile bottom. Larger pile diameter and higher material strength can improve the bearing capacity of composite subgrade. But different layouts of chemical churning piles and whether to set up Goodman interface element have little influence on bearing capacity of composite subgrade.

Key words: chemical churning pile, composite subgrade, bearing characteristics, three-dimensional numerical analysis