Assessment of Stress-Strain Behavior of Energy Piles Installed in Sand

Abstract

ABSTRACT:The geothermal piles are dual functional geostructures which provide sub-structural support to the building and also fulfill the energy demands in terms of its climate control. For efficient design of geothermal piles, it is necessary to evaluate the thermo-mechanical behavior of geothermal piles. The purpose of this study is to evaluate the behavior of geothermal heat exchanger pile installed in sand, subjected to a coupled thermomechanical loading. Initially, in this study a full scale field test is simulated and results are compared. In the second phase, parametric study by varying mechanical and thermal loading on the geothermal pile placed in dense sand, is performed. In this study, the sand and geothermal pile are simulated as axis-symmetrical models, where pile is considered to be thermo-elastic in nature and sand is considered as Mohr-Coulomb elastic-plastic material. Coupled Temperature-Displacement analysis is applied in order to simulate the observed experimental results. It is shown that the simulated model is able to reproduce the major thermo-mechanical effects for the selected full scale model approximately. Stress and strain behavior along with the depth of energy pile induced by thermo-mechanical loading has been reported. It was concluded that when mechanical load value is comparatively low, the thermal variation influences the induced axial stress while at higher mechanical load the stress behaviour is nearly constant at different temperature variation.

Thermo-Mechanical Performance of a Phase Change Energy Pile in Saturated Sand

“…In order to study the thermo-mechanical characteristics of energy piles, researchers have proposed a number of models, including solid cylindrical models [19,20], annular cylindrical heat source models [21], composite cylindrical models [22], composite toroidal coil source models [23], the transient coil source model [6], and other numerical models that consider the heat transfer of the circulating fluid in the pipeline. Many critical parameters, such as thermal loads, soil properties, head load, etc., were analyzed and the numerical results generally agreed well with the corresponding test's results [24]. In most cases, the applicability and accuracy of numerical methods for investigating energy piles were validated.…”

“…The phase change material can absorb or release heat by changing its state (phase change) without changing the temperature. Using phase change paraffin in energy piles not only can improve heat storage capacity and heat exchange efficiency of the piles, but can also reduce the uneven temperature change of the pile body by the phase change action, and thereby reduce the uneven axial stress [24]. Despite the demand for energy piles increasing, the potential use of this relatively new technology of phase change materials in energy piles is challenging, as there is a lack of reliable information concerning the thermo-mechanical behaviors of PC energy piles under different thermal loading conditions.…”