Thermomechanical Behavior of Energy Piles and Interactions within Energy Pile–Raft Foundations

Abstract

Energy pile groups generally show different behavior than single energy piles because of the presence of rafts and the thermomechanical interaction between piles. This paper presents the results from a series of full-scale field tests to investigate the thermomechanical behavior of an energy pile–raft foundation. The energy pile group was nonsymmetrically operated to analyze the thermally induced group effects. A nonuniform temperature increase may induce a significant change in the distributions of the thermal stress and mobilized shaft resistance. This paper demonstrates that group effects between energy piles can trigger effects in the pile-raft foundation. The nonsymmetrical thermal loading induces a differential displacement in the foundation. When the number of operating piles increases, a lower thermal stress develops along the operating pile and the differential displacement decreases. In addition, because of the indirect heating of the surrounding piles, the differential displacement will continuously decrease during long-term operation, and the thermal stress on the surrounding, nonoperating piles gradually becomes crucial.