| Ground-source heat pumps (GSHPs) installed into the foundations or subsurface walls of a structure are a particularly promising technology to help reach the goal of increasing energy efficiency in the United States by 20% in the next 20 years. Although "energy foundations" may be a feasible technology to improve the energy efficiency of building heating and cooling systems, a potential issue which may be encountered is the soil-structure interaction related to the expansion and contraction of the concrete and surrounding soil during heating and cooling, respectively. The possibility for plastic thermal deformations in the soil surrounding the foundation poses a risk to the engineering performance of energy foundations, and deserves careful consideration. This requires a more detailed understanding of the recoverable and irrecoverable thermal strains encountered by a soil specimen during heating while under different loading conditions. This study involves the development of a new thermo-hydro-mechanical cubical cell, and its use to evaluate the impact of initial stress state anisotropy on the thermally induced volume change in saturated soils. Specifically, thermal heating and cooling tests were performed on water-saturated, compacted silt specimens under four initial plane strain Ko conditions. The results from these tests were compared between each other and with predictions from a modified thermo-elasto-plastic model to evaluate the impact of initial stress state anisotropy on the thermally-induced volume change in saturated soils. |
