Thermo-mechanical analysis of pipe energy piles in layered cross-isotropic soils

Abstract

This paper aims to propose a method for the thermo-mechanical analysis of pipe energy piles in layered cross-anisotropic soils. Firstly, the pipe pile is modelled as a bar and the stiffness matrix equation considering thermo-mechanical loads is established based on the finite element method (FEM). The soils are considered to be layered cross-anisotropic and the boundary element method (BEM) is employed to obtain the deformation-force relationship of the soil-pile nodes. Afterwards, the coupled BEM-FEM equation is developed according to soil-pile deformation coordination conditions. The proposed method is verified with responses of pipe piles, solid energy piles and pipe energy piles. Parametric analyses show that the performance of the pipe energy pile induced by heating needs considering in the design of the pipe pile thickness, and the induced tensile stress should be taken into account in the design in hard soils. Besides, the influence of cross-anisotropy on the performance of the pile under cooling is larger than that under heating, and a softer surface soil layer yields a smaller axial force of the pipe energy pile for layered soils.