Investigation on the Thermo-Mechanical Behavior of an Energy Pile and the Surrounding Soil by Model Test and 2D Finite Element-Finite Difference Method

Abstract

The exploitation of geothermal energy could cause additional thermal load imposed to the foundation and surrounding soils. The effects of temperature changes on the response of energy piles which can induce thermal expansion and contraction of both piles and soils need to be examined. This study investigated the behaviors of an energy pile and the surrounding soil using the model test and 2D thermo-hydro-mechanical finite element-finite difference (FE-FD) method that can solve soil-water-temperature coupling problems based on three phase field theory. In the numerical analysis, the thermo-mechanical property of soil could be described by a new thermo-elastoplastic constitutive model, in which, the concept of equivalent thermal stress was adopted. Time change of temperature and displacement of the pile and soil, axial stress of pile are investigated. The simulated results are in good agreement with those obtained from the laboratory test on a model energy pile. Attention is dedicated to the development of pore water pressure that could cause thermo-consolidation of soil and bring the settlement of pile-soil system. In some circumstances, long-term instability of the pile-soil might happen through years of heating and cooling cycles.