Investigation of in situ thermomechanical behaviors of soil around an energy pile with flat dilatometer tests.

An energy pile alters the ground temperature fields around it, which may lead to uneven settlements and a higher risk of failure. The thermomechanical behaviors of soils have been studied extensively in laboratory experiments, while in situ investigations are rare. In this research, flat dilatometer tests (DMTs) are first employed to investigate the thermomechanical behaviors of soil under in situ conditions. The soils were heated by a full-scale precast high-strength concrete (PHC) energy pile, and a series of DMTs were conducted. The results show that temperature changes had a substantial impact on the DMT data of the silt and clay layers. The measured pressures p0 and p1 of the silt and clay layers decreased with increasing ground temperature, and the measured pressure p2 of the silt and clay layers decreased at the beginning and then increased with increasing ground temperature. Although the silt and clay layers have similar variations in the measured pressures, the clay layer has a greater thermal response than the silt layer. Finally, the critical state soil mechanics theory is used to analyze the pore water pressure and thermomechanical properties of in situ overconsolidated soil. The results indicate that the elastic region (yield surface) and mean effective stress of in situ soil decrease with increasing ground temperature, potentially resulting in more irreversible deformation and a higher probability of failure. [ABSTRACT FROM AUTHOR]