A modified analytical solution of soil stress distribution for XCC pile foundations

Abstract

X-section cast-in-place concrete pile (XCC pile) is a new type of pile foundation, which has an X-shaped cross section. Compared to the traditional circular pile of the same cross-sectional area, the bearing capacity of an XCC pile is higher due to increased cross-sectional perimeter. Since Geddes solution is based on St. Venant’s principle, leading to the results independent of the cross-sectional geometry and size, large differences are induced when estimating the soil stress distribution for XCC pile foundations. This paper derives a modified analytical solution, which is dependent on the cross-sectional geometry of XCC pile, from Geddes solution. Validation of this modified solution was conducted through three-dimensional numerical analysis and proven more suitable for XCC pile foundations. Parametric study on three geometrical parameters is conducted using this modified solution. The results indicate that the stress in founding soil due to skin friction decreases with increasing pile radius and central angle of concave, but increases with increasing length of flat side. The stress due to end-bearing decreases with increasing pile radius and length of flat side, but increases with increasing central angle of concave. From the parametric studies, the recommended dimensions of XCC pile radius, length of flat side, and central angle of concave are recommended ranges from 200 to 600 mm, 30 to 60 mm, and 90° to 150°, respectively.