Temperature effects on pile–soil interface behaviour in the case of piles in sand

Abstract

The effects of increased temperature on the stress–strain response of geothermal piles and supporting soil were studied in this work. Geothermal piles with different pile end supports were investigated numerically using the finite-element software Abaqus. A critical-state-based constitutive model (clay and sand model) was adopted for simulating the elasto-plastic thermomechanical behaviour of soil using two user-defined material subroutines (UMAT and UMATHT). In order to understand the additional stresses and strains in piles and soil due to thermal loading of piles, a set of parametric investigations was carried out for different values of the restraint at the pile base, the relative density of the sand, pile length, pile diameter and the coefficient of lateral earth pressure of the soil. An increased coefficient of lateral earth pressure in the soil at the pile–soil interface was observed due to circumferential thermal radial strains over the pile length. Furthermore, the thermal response of the piles and soil was found to depend on the soil's relative density and the magnitude of thermal load experienced by the piles. Cyclic thermal loading resulted in increased axial stresses in the piles.