Abstract
The thermo- mechanical behavior of energy piles has been studied extensively in recent years. In the present study, a numerical model was adapted to study the effect of various parameters (e.g. heating/cooling temperature, head loading condition and soil stiffness) on the thermo-mechanical behavior of an energy pile installed in unsaturated sandstone. The results from the simulations were compared with measurements from a thermal response test on a prototype energy pile installed beneath a 1-story building at the US Air Force Academy (USAFA) in Colorado Springs, CO. A good agreement was achieved between the results obtained from the prototype and the numerical models. A parametric evaluation were also carried out which indicated the significance of the stiffness of the unsaturated sandstone and pile’s head loading condition on stress-strain response of the energy pile during heating/cooling cycles.
Highlights
In recent years, reinforced concrete piles have been widely used as geothermal heat exchangers to access the relatively constant temperature of the ground for efficient heating and cooling of buildings [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]
Considering the fact that a pile foundation may be subjected to different vertical loads, it is essential to consider the effect of overlying structures on thermo-mechanical response of an energy pile
As observed in this figure, the resistance of the surrounding soil may have a significant influence on the distribution of the thermal axial stress and strain profiles which is almost similar to the effect of overlying structure
Summary
In recent years, reinforced concrete piles have been widely used as geothermal heat exchangers to access the relatively constant temperature of the ground for efficient heating and cooling of buildings [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]. Deformation in energy piles is a complex process due to interaction between soil and pile and the effects of temperature change on the thermal expansion and contraction of the pile and surrounding subsurface. Deformations in this case may occur due to initial mechanical loading associated with construction of the overlying building, and thermo-elastic expansion and contraction of the reinforced concrete during heating and cooling, as well as settlement or heave of the surrounding subsurface. This study seeks to examine these two aspects by means of a 2D finite difference analysis to predict the deformation behavior of an energy pile during thermo-mechanical loading
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