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Field test of a floating thermal pile in sensitive clay

Bergström, Anders ; Javed, Saqib LU and Dijkstra, Jelke (2021) In Geotechnique 71(4). p.334-345
Abstract
The response of floating pile foundations in deep deposits of soft clay is governed by the settlements within the clay deposit surrounding the piles. A long-duration thermal response test (TRT) has been performed to assess the impact of heating and cooling on the geotechnical performance of a vertically loaded slender tubular steel pile in a deep deposit of sensitive clay. The results from the instrumented test site indicate that negligible excess pore water pressures, up to 3 kPa during heating and down to −1·1 kPa during cooling, were generated in the soil adjacent to the pile for a 50 W/m heat flux. The heating rate was sufficiently low to facilitate the drainage of pore water. The influence radius for the excess pore water pressures,... (More)
The response of floating pile foundations in deep deposits of soft clay is governed by the settlements within the clay deposit surrounding the piles. A long-duration thermal response test (TRT) has been performed to assess the impact of heating and cooling on the geotechnical performance of a vertically loaded slender tubular steel pile in a deep deposit of sensitive clay. The results from the instrumented test site indicate that negligible excess pore water pressures, up to 3 kPa during heating and down to −1·1 kPa during cooling, were generated in the soil adjacent to the pile for a 50 W/m heat flux. The heating rate was sufficiently low to facilitate the drainage of pore water. The influence radius for the excess pore water pressures, however, extended beyond the soil volume affected by temperature change. The absence of thermally triggered creep settlements could be explained by the overlap between the remoulded zone resulting from pile installation, the extent of the heating, and the low creep susceptibility of remoulded sensitive clay for moderate temperature changes. Furthermore, no difference in the ultimate bearing capacity was found between the thermal pile and the reference pile, which was only loaded with a serviceability load during the test series. The current test data, therefore, indicate that driven floating piles in a deep deposit of soft clay also function as heat exchanger piles with minimal detrimental effects, for similar operational conditions as used in the TRT. It should be noted, however, that other pile types that do not extensively remould the clay adjacent to the pile shaft may show more significant influence of the thermal changes. (Less)
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publication status
published
subject
in
Geotechnique
volume
71
issue
4
pages
334 - 345
publisher
ICE Publishing
external identifiers
  • scopus:85102949480
ISSN
0016-8505
DOI
10.1680/jgeot.19.P.094
language
English
LU publication?
yes
id
9e8f5e05-efb0-4f51-9616-0a26b30478ba
date added to LUP
2020-06-11 19:27:31
date last changed
2021-03-30 13:39:41
@article{9e8f5e05-efb0-4f51-9616-0a26b30478ba,
  abstract     = {The response of floating pile foundations in deep deposits of soft clay is governed by the settlements within the clay deposit surrounding the piles. A long-duration thermal response test (TRT) has been performed to assess the impact of heating and cooling on the geotechnical performance of a vertically loaded slender tubular steel pile in a deep deposit of sensitive clay. The results from the instrumented test site indicate that negligible excess pore water pressures, up to 3 kPa during heating and down to −1·1 kPa during cooling, were generated in the soil adjacent to the pile for a 50 W/m heat flux. The heating rate was sufficiently low to facilitate the drainage of pore water. The influence radius for the excess pore water pressures, however, extended beyond the soil volume affected by temperature change. The absence of thermally triggered creep settlements could be explained by the overlap between the remoulded zone resulting from pile installation, the extent of the heating, and the low creep susceptibility of remoulded sensitive clay for moderate temperature changes. Furthermore, no difference in the ultimate bearing capacity was found between the thermal pile and the reference pile, which was only loaded with a serviceability load during the test series. The current test data, therefore, indicate that driven floating piles in a deep deposit of soft clay also function as heat exchanger piles with minimal detrimental effects, for similar operational conditions as used in the TRT. It should be noted, however, that other pile types that do not extensively remould the clay adjacent to the pile shaft may show more significant influence of the thermal changes.},
  author       = {Bergström, Anders and Javed, Saqib and Dijkstra, Jelke},
  issn         = {0016-8505},
  language     = {eng},
  number       = {4},
  pages        = {334--345},
  publisher    = {ICE Publishing},
  series       = {Geotechnique},
  title        = {Field test of a floating thermal pile in sensitive clay},
  url          = {http://dx.doi.org/10.1680/jgeot.19.P.094},
  doi          = {10.1680/jgeot.19.P.094},
  volume       = {71},
  year         = {2021},
}