Investigation of Thermal Loading Effects on Shaft Resistance of Energy Pile Using Laboratory-Scale Model

Abstract

Cyclic temperature changes in an energy pile generate cyclic thermal expansive and contractive strains along the interface, which may impact both the serviceability and the ultimate pile resistance. This paper aims to assess induced changes in the shaft resistance of an energy pile after being subjected to different temperature variation, between 24°C and 34°C. This was done by measuring the load-settlement curve of a laboratory-scale floating energy pile installed in fully saturated normally-consolidated (NC) kaolin. A 10% relative settlement criterion was adopted to define the shaft resistance. Changes in temperature and pore pressure were also monitored in the surrounding clay using embedded thermocouples and a pore pressure transducer. Measurements during thermal loading showed that a positive excess pore water pressure was generated during the first thermal cycle followed by a negative pore pressure (suction) during the same cycle, while subsequent thermal cycles generated a cyclic pore pressure that remained negative regardless of the number of thermal loading cycles. It was also observed that piles subjected to heating exhibited greater shaft resistance than the reference pile tested at room temperature. Although the shaft resistance was considerably influenced by cyclic thermal loading, increasing the number of thermal cycles did not make appreciable differences in shaft resistance.