An analytical solution for the consolidation of a composite foundation reinforced by vertical drains and high replacement ratio gravel piles by considering the radial flow within gravel piles

To make up for the shortcomings of single-pile composite foundations, combined composite foundations are increasingly used in engineering. However, studies for the consolidation theory of composite foundations reinforced by high replacement ratio gravel piles and vertical drains, in which the radial flow within gravel piles is considered, have been rarely reported in the literature. The establishment of a comprehensive composite foundation consolidation model is of significance for more reasonable design for stone columns and vertical drains, such as penetration depth, replacement ratio, distribution pattern and so on. Therefore, to solve such consolidation issues, a gravel pile-soil unit with several vertical drains around the perimeter is regarded as a calculation model. Then, the related analytical solution to the total average express pore water pressure (EPWP) is derived by considering the radial flow within gravel piles, and the reliability is verified by comparison with existing solutions. Moreover, extensive calculations are made to investigate the consolidation behaviors, and the results show that vertical flow in soils has little effect on the consolidation of this composite foundation; the effect of radial flow within high replacement ratio gravel piles is nonnegligible; installing vertical drains between piles can enhance the consolidation rate. Finally, the model is applied to the settlement calculation of an embankment in Malaysia, and the results by proposed solutions are in good agreement with the measured data, further indicating the applicability of the calculated model.