Abstract: Most research on composite foundations reinforced with multiple reinforcements focuses on the combination of drainage piles with undrained piles. There is limited theoretical research on the consolidation of composite foundations enhanced by multiple drains with varying drainage capacities. In this study, we investigate a composite foundation improved by stone columns in conjunction with prefabricated vertical drains (PVDs). Assuming equal strain, we establish an analytical model for consolidation with two-way radial drainage, taking into account radial-vertical seepage within the stone column. Analytical solutions for pore pressure and consolidation degree under transient loading are derived and validated through degradation analysis and measurement comparisons. The research findings on consolidation behavior indicate that utilizing multiple types of drains can significantly expedite foundation consolidation compared to a single-drain composite foundation. Neglecting radial seepage in the stone column for larger diameter piles may lead to an overestimation of the consolidation rate. Due to the two-way seepage of water in the soil, pore pressure in the soil of multiple reinforcements composite foundations initially increases and then decreases along the radial direction. The peak radial coordinate gradually shifts towards the plastic drainage plate with depth, with the trend weakening as consolidation progresses.

Key words: composite foundation, consolidation, multiple types of drains, stone column, prefabricated vertical drains (PVDs)