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research article

Centrifuge modelling of heating effects on energy pile performance in saturated sand

Ng, W.W. C.
•
Shi, C
•
Gunawan, A
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2015
Canadian Geotechnical Journal

The operation of energy pile in summer can expel excessive heat of the buildings into the ground by the use of a heat pump. Despite of having been implemented for decades, the design of energy pile still relies heavily on empiricism as there is still limited understanding about heating effects on pile capacity. A series of centrifuge model tests in saturated sand is reported in this study to investigate heating effects on the settlement patterns as well as capacities of single piles. In total, four in-flight pile load tests under different temperatures (i.e. 22℃, 37℃ and 52℃) were carried out. Variations of pile capacity were interpreted with the help of a non-linear elastic analysis. The test results show that after heating at zero applied axial load, toe resistance of pile was mobilized as a result of constrained downward thermal expansion of pile. Heating to a higher temperature caused thermally induced the neutral plane (NP) to shift towards the pile toe. It is also found that for pile under a maintained working load, a temperature increase of 30℃ made the pile head initially heave by 12.5 mm and gradually settle by 5.1 mm after 4 months of continuous heating. The post pile settlement is believed to be caused by thermal contraction of sand. Subsequent pile load tests showed that pile capacity increased by 13% and 30% with an incremental temperature of 15℃ and 30℃, respectively. With an increasing temperature, shaft resistance increased but at with a reducing rate. At a higher temperature increment, In contrast, toe resistance increased more rapidly than shaft resistance due to a larger downward expansion of the pile at higher temperature increment. For simplicity, earth pressure coefficient with a value of 1.1K0 and 1.3K0 was found to be suitable for estimating the capacity of model pile with a temperature increment of 15℃ and 30℃, respectively.

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Type
research article
DOI
10.1139/cgj-2014-0301
Web of Science ID

WOS:000358606100004

Author(s)
Ng, W.W. C.
Shi, C
Gunawan, A
Laloui, Lyesse  
Hanlong, L.
Date Issued

2015

Publisher

National Research Council Canada

Published in
Canadian Geotechnical Journal
Volume

8

Issue

52

Start page

1045

End page

1057

Subjects

energy pile

•

capacity

•

centrifuge modelling

•

heave

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
LMS  
Available on Infoscience
December 4, 2014
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/109211
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