Numerical Investigation of the Load Movement and Ultimate Load of Energy Piles Embedded in Sand

Even though the energy pile is known as an efficient dual-purpose system nowadays, the interactive response under simultaneous mechanical and thermal loads requires further investigation. An attempt has been made to evaluate the effect of different factors on load-displacement response and bearing capacity, including different loading conditions, pile geometry, and ground conditions using a three-dimensional (3D) numerical model. The energy pile model was validated and then subjected to thermal loadings of +10°C, +20°C, and −10°C in saturated and dry sandy soil with different relative densities and coefficients of thermal expansion. In addition, analyses were carried out in conditions from the tip of the pile being embedded in very loose sand to being embedded in a rock-hard layer to provide a comprehensive coverage of all the scenarios in engineering practice. Results indicate that the ultimate bearing capacity of the energy pile can increase by 25.5% or decrease by 13% depending on the applied temperature and geotechnical conditions. When the pile is heated and cooled, the bearing capacity increases and decreases, respectively, while for the piles placed in dense and saturated sand, sand with a larger thermal expansion coefficient, or socketed into a very hard layer with 60 to 100 times higher elastic modulus compared with the upper layer, the effect of thermal loads on the pile bearing capacity are more noticeable. Results show that in piles with a smaller diameter, the temperature variation effects are slightly higher. The findings of the study are useful for engineers in design practice to optimize the performance of energy piles under different conditions.