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

Abstract

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.