Thermomechanical Behavior of Parallel Multi-U-Shaped Energy Piles Under the Summer Condition

Abstract

As a green and sustainable geothermal development technology, energy piles have received wide attention in the field of energy underground structure engineering. This work examines the variation rules of the pile-soil temperature, stress-strain, side friction resistance, and pile-top displacement of a full-scale parallel multi-U-type energy pile under the action of temperature loading using a combination of numerical modeling and field testing. As the number of parallel U-type heat exchanger tubes increases, the temperature of the energy pile body rises. However, after a certain number is reached, the effect of additional increases on the temperature rise of the pile body decreases. Additionally, there is a phenomenon known as thermal interference between the heat exchanger tubes, which should be kept at a suitable distance to minimize their mutual influence. The parallel 5U-type energy pile’s temperature is fairly evenly distributed along the depth direction, and the strain of the pile body demonstrates that the two ends of the pile body change in size, with the middle end having the largest restraining stress. When combined with the change in pile side resistance, this location is thought to produce the displacement’s zero point. The pile top displacement increases by 0.65 mm for every 5 °C increase in the water entry temperature.

Keywords

• energy pile
• parallel multi-U-shaped buried pipe
• numerical simulation
• heat accumulation
• thermomechanical behavior