A semi-analytical solution for the load-transfer behaviors of precast concrete pile reinforced by cemented soil with long-core in layer soils

Precast Concrete Piles Reinforced by Cemented Soil (PCCS), a novel composite pile, has been widely employed for soft ground treatment. In this technique, the precast concrete (PC) pile is installed in the center of a deep mixing (DM) column, thereby effectively harnessing the benefits of both technologies. However, modelling the load transfer of the composite pile is quite complex due to the different materials (soft soil, cemented soil and concrete) and interfaces (soft soil-cemented soil, soft soil-concrete, cemented soil-pile) involved. Particularly, studies on the axial load-transfer behavior of the PCCS with long-core (inner core), in which the PC piles is significant longer than the DM columns, remain limited. This contribution proposes an 1D semi-analytical load transfer model for the PCCS with long-core in layered soils, which takes into account the shear force transfer at the different interfaces and the mechanical behavior of the natural soil, cemented soil, the pile and the interface. By comparing and analyzing the mechanical responses of PCCSs under loads applied to the inner core head (loading mode I) and the entire cross-section of the PCCSs (loading mode II), the ability of the model to describe the experimental behavior is investigated. The results indicate that the distribution of the axial force along the pile shaft and the skin friction resistance at the interfaces of the PCCS with long-core can be realistically reproduced by the model. It is observed that the ultimate bearing capacity of the PCCS under loading mode II is about 15% higher than that under loading mode I.