Soil thermal response to temperature cycles and end boundary conditions of energy piles

Mohammed Faizal, Aria Moradshahi, Abdelmalek Bouazza, John S. McCartney

Research output: Contribution to journalArticleResearchpeer-review

10 Citations (Scopus)

Abstract

This paper explores the influence of building cover and pile toe boundary conditions on ground temperature distributions surrounding energy piles. Experimental and numerical studies were conducted on two isolated cast-in-place energy piles installed in dense unsaturated sand, one exposed to the atmosphere at the ground surface (diameter=0.6 m and length=16.1 m) and the other installed under a six-story building (diameter=0.6 m and length=10 m). Investigations were conducted for monotonic heating and daily cyclic temperature changes of the piles ranging between 10°C and 35°C. The changes in ground temperature decreased as radial distance increased from the edge of both piles. Cyclic temperatures in both piles induced lower ground temperature changes and decreased the radial thermal influence zone compared with monotonic heating. However, the radial thermal zone in cyclic operating mode can be influenced by different ratios of heating to cooling times and hence should be selected carefully to avoid unexpected ground temperature changes. Atmospheric effects were observed up to a depth of 2 m for the energy pile exposed to the atmosphere. The insulation provided by the building footprint slightly decreased the impacts of ground-atmosphere interaction on the soil temperature distribution with depth near the surface compared to the energy pile exposed to the atmosphere. The ground temperature variations were dominant along the length of the heat exchanger loops for both piles. However, they were negligible near the pile toe below the heat exchanger loops for both piles.

Original languageEnglish
Article number04022027
Number of pages14
JournalJournal of Geotechnical and Geoenvironmental Engineering
Volume148
Issue number5
DOIs
Publication statusPublished - May 2022

Keywords

  • End boundary conditions
  • Energy piles
  • Ground temperatures
  • Radial thermal influence zone
  • Temperature cycles

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