Numerical investigation of axial bearing capacity of piles embedded in sloping ground

Abstract

In practice, piles may be constructed in sloping ground where the axial capacity of piles may be affected by the ground slope. This paper presents the effect of the ground slope geometry on the ultimate axial bearing capacity of vertical pile using numerical simulation based on Plaxis 3D Foundation software. The pile is assumed to consist of linear and elastic material. Various aspect ratios (L/D) for the pile have been considered. The soil behavior is modeled based on the Mohr Coulomb failure criterion. Loose and dense sand, and sandy clay have been used for numerical modeling. Interface elements have been applied to the pile-soil boundaries to accommodate the slip which may occur between these two materials. The simulation of the pile-soil system is first calibrated using available data from the field load tests on piles to ensure the validity of the constructed numerical modeling. Various shapes for the ground slope have been considered in analyses, including flat- sloping, uniformly sloping, all-around upward sloping, and all-around downward sloping ground. The results have shown that the pile axial capacity increases with increase in the value of the upward sloping. In contrast, the pile capacity decreases with increase in the downward sloping. From a provided data base, empirical expressions have been presented to take into account the slope shape effect on the pile capacity. It has been found that this empirical expression can be confidently used in practice to account for the ground sloping effect on the pile capacity. This expression may be used in conjunction with conventional methods based on the limit equilibrium approach. This is interesting since practicing engineers are well familiar with conventional methods calculating the pile axial capacity. Key words: Pile, ground slope, axial capacity, pile, Mohr Coulomb, numerical method, finite element, Mohr Coulomb failure criterion.