Abstract: To analyze the settlement and deformation characteristics and the failure modes of embankments on soft ground reinforced by plain concrete piles, three centrifugal test models of the embankments on soft ground reinforced by plain concrete piles with different spaces between piles and their numerical models have been performed. The results show that changing pile spacing has a remarkable effect on the settlement and deformation, the pile shaft strain, the failure modes of piles and reinforced cushion of the models, under embankment self-weight load, and track structure and vehicle load. When the pile spacing is not greater than 4 times of the pile diameter, the reinforced cushion can basically maintain integrity, the settlement of the models gradually tends to stabilize. Once the pile spacing increases to 6 times of the pile diameter, the reinforced cushion is impaled, the function of deformation coordination and load transfer would not be available, resulting in a continual increase of the settlement of the model embankments. While the pile spacing reaches 4 times of the pile diameter, an abrupt decrease in the maximal strain value of the piles occurs with increasing upper load, and the plain concrete piles near the embankment toe fail firstly in bending failure mode rather than shear failure mode. The plain concrete piles closer to the embankment center fail gradually in bending failure mode as the pile spacing increases to 6 times of the pile diameter.

Key words: composite foundation, plain concrete pile, reinforced cushion, deformation and failure modes