Combined load bearing capacity of rigid piles embedded in a cross-anisotropic clay deposit using 3D finite element lower bound

Abstract

In this study, an iterative-based three-dimensional finite element lower bound in association with the second-order cone programming method is adopted to evaluate the limit load of a single pile embedded in cross-anisotropic soils under general loading condition. The lower bound solutions of the pile embedded in an anisotropic soil deposit can be found by formulating the element equilibrium, equilibrium of shear and normal stresses along discontinuities, boundary conditions, yield function, and optimizing the objective function through the second-order cone programming method in conjunction with an iterative-based update procedure. A general loading condition is considered to profile the expansion of the safe load in the vertical-horizontal-moment (V–H–M) space. The results of this study are compared and validated against three different cases including an isotropic lateral loading, anisotropic end bearing capacity, and a pile embedded in an isotropic soil deposit under general loading condition. A parametric study is conducted to evaluate the impact of different influencing factors. It was found that the effect of anisotropy on the variation of lateral limit load of a single pile is more pronounced than the corresponding vertical and bending moment limit loads, whereas the interface properties have more significant effects on the vertical and bending moment limit loads in comparison to the lateral limit load.

Keywords

• Rigid pile
• Cross-anisotropy
• Clay
• Combined loading
• Three-dimensional finite element lower bound