Small-Scale Modeling of Thermomechanical Behavior of Reinforced Concrete Energy Piles in Soil

Small-scale physical model tests have been increasingly used to study the thermomechanical soil-pile interaction, but existing model piles are highly simplified and do not have representative thermal properties or the quasi-brittle mechanical behavior of RC. This study aims to overcome these shortcomings by presenting a new type of model RC. This consists of a mortar (plaster, sand, and water) with copper powder added to tune the mixture's thermal properties, along with a steel reinforcing cage. Fine sand was used to represent geometrical scaling of the prototype aggregates to correctly capture the quasi-brittle structural response. Adding copper powder content of 6% (by volume) matched the coefficient of thermal expansion and thermal conductivity of prototype concrete without changing the axial and flexural properties of model piles. In 1g soil-structure interaction tests, the model pile was able to serve as an effective heat exchanger for transferring heat from a water-carrying pipe embedded within the mortar to the surrounding soil. The model RC exhibited cyclic pile head settlement due to repeated pile heating and cooling.