Vertically-loaded single floating pile in layered soils by thin annulus element method

Based on the thin annulus element method and the hypothesis of fictitious soil pile, a model for the settlement of an axially-loaded single floating pile in the layered soils is proposed. The soil column beneath the floating pile is regarded as the fictitious pile shaft. The soil-pile system is then divided into the separate thin-layer elements. The stiffness matrices for the soil element and pile element are deduced using the principle of virtual displacements. The global matrices are constructed by considering the continuity and equilibrium conditions between the elements. The vertical displacement of the soil-pile system can be obtained by solving the matrix equation. The comparisons of the results between the proposed model and the available solutions indicate the accuracy of the proposed model. Parametric study shows that the accuracy of the proposed solution depends greatly on the thickness of the thin annulus element and the choice of the displacement function. For the floating pile in the three-layer soil, the bearing capacity of the middle layer around the shaft increases with the increase of its elastic modulus. The tip stiffness of the floating pile increases with the decrease of the layer thickness between the pile tip and bedrock. When this thickness is less than 0.3 times the soil thickness, the pile tip stiffness will increase significantly. The pile tip stiffness is also dependent greatly on the properties of the underlying soil below the tip of the floating pile.