Coupled BEM-FEM analysis of horizontally loaded energy piles in cross-anisotropic layered soils

The performance of an energy pile in cross-anisotropic soils under horizontal loading is analyzed in this study. Firstly, the finite element method (FEM) is used to discretize the energy pile, and the Timoshenko beam theory coupled to the axial force bar element is applied to simulate the pile element. Secondly, by assembling the stiffness matrix of the pile element, the global stiffness matrix equation of the horizontally loaded energy pile is established. Flexibility coefficients of soils are obtained by using the extended precise integration method (EPIM), which will be utilized as the kernel function of the boundary element method (BEM). Then, the coupled BEM-FEM equation is established by introducing the soil-pile deformation coordination conditions and force balance at the soil-pile interface. By solving the equation, the stress and deformation solutions of the energy pile can be further obtained. Finally, some numerical examples are analyzed to verify the correctness of the presented theory, and the effects of the load ratio of horizontal loading to thermal loading, cross-anisotropic thermal parameters, the stratification of soils, pile flexibility factors and length-diameter ratios are investigated.