Comparative Study on the Thermomechanical Behavior and Bearing Capacity of Energy Piles in Dry and Moist Soil Conditions

This paper investigates the impact of pile temperature and soil moisture on pile behavior during gradual loading and unloading, using 1 g physical model tests. The findings provide insights into the behavior and bearing capacity of energy piles. Each test involves increasing the mechanical head load on the pile from 15 to 515 N in 10 steps, followed by a gradual unloading back to 15 N. Tests are conducted at three pile temperatures (15.5 °C, 21.5 °C, and 27.5 °C) and under two ground conditions (air-dried silty sand and 70% initial saturation silty sand), totaling six tests. The results demonstrate a strong linear positive correlation between pile temperature and bearing capacity in both dry and moist soil. Higher temperatures can enhance the pile’s sleeve strength and its activation at greater headloads. The study introduces a new parameter, the pile tip behavior index, to estimate the soil’s elastic/plastic state based on changes in vertical and lateral soil pressure under the pile tip. The influence of soil temperature and moisture on the lateral earth pressure coefficient at rest (K0) beneath the pile tip is also examined. Pile loading has minimal impact on K0 in dry conditions but reduces it in moist conditions, with unloading leading to an increase in K0 in both scenarios.