Abstract: Based on the axisymmetric consolidation model with the inward radial flow in the soil around a vertical drain, the consolidation equations of the composite ground with long vertical drains and short impervious columns under time-dependent loading were presented. The analytical solutions for consolidation of this combined composite foundation were derived under the single-sided drainage condition, including the solutions for the excess pore water pressures within the vertical drain and the surrounding soil, and for the overall average consolidation degree of the composite foundation. The rationalities of the proposed solutions were verified by 3D FEM simulations. The main influencing factors were analyzed using the proposed solutions, and the consolidation characteristics of the combined composite ground were also investigated. The results show that the consolidation rate of the combined composite foundation increases gradually with the increasing penetration ratio of the short impervious columns and decreases with the increases in the well resistance and the thickness of the smear zone. The variations in the stiffness and replacement ratio of the short impervious columns have less effect on the consolidation rate of the composite foundation.

Key words: combined composite foundation, consolidation, analytical solution, impervious column, vertical drain