Mechanical behaviour of a small-scale energy pile in saturated clay

Yavari, Neda; Tang, Anh Minh; Pereira, Jean‐Michel; Hassen, Ghazi

doi:10.1680/jgeot.15.t.026

Cited by 67 publications

(28 citation statements)

References 38 publications

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“…A number of small-scale physical model studies have characterized the axial thermal response of energy piles for monotonic heating (McCartney and Rosenberg, 2011;Ng et al, 2014b;Goode and McCartney, 2015) and cyclic temperatures (Kalantidou et al, 2012;Ng et al, 2014a;Stewart and McCartney, 2014;Yavari et al, 2014Yavari et al, , 2016aNg et al, 2016;Wang et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

“…Another reason for the stable responses of the thermal strains towards the end of experiments is that there were no head loads on the pile or end restraints in the present study. According to some physical model studies with thermal cycles on energy piles (Kalantidou et al, 2012;Stewart and McCartney, 2013, Yavari et al, 2014, 2016aWang et al, 2016), thermally induced settlement is reversible for pile head loads corresponding to as low as 20% of the pile ultimate resistance, and becomes irreversible for higher pile loads, particularly for loads closer to the ultimate pile resistance. However, the soil type plays an important role in the thermal response of the pile, and the dense sand at the current site likely contributed to the relatively high resistance to axial thermal deformations.…”

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confidence: 99%

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Axial and Radial Thermal Responses of a Field-Scale Energy Pile under Monotonic and Cyclic Temperature Changes

Faizal

Bouazza

Haberfield³

et al. 2018

J. Geotech. Geoenviron. Eng.

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The axial and radial thermal responses of a field-scale energy pile installed in dense sand and subjected to monotonic and cyclic temperatures are examined. It is found that the axial thermal strains in the pile are more restricted to thermal expansion/contraction compared to radial thermal strains. The radial thermal strains are close to that of a pile expanding/contracting freely, indicating minimal resistance from the surrounding soil in the radial direction. As a result, very low magnitudes of radial thermal stresses developed in the pile compared to axial thermal stresses. The pile-soil radial contact stresses estimated from cavity expansion analysis are up to 12 kPa for a pile temperature change of 22.5 o C and are likely negligible for the range of commonly-encountered operating temperatures of energy piles installed in dense sand. During cyclic heating and cooling, unstable changes in axial and radial thermal strains were observed initially during initial cycles indicating a ratcheting response. The changes in strains became more stable over further cycles, without significant changes in side friction, pile-soil contact stresses, or strength of the dense sand.

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Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

Axial and Radial Thermal Responses of a Field-Scale Energy Pile under Monotonic and Cyclic Temperature Changes

Faizal

Bouazza

Haberfield³

et al. 2018

J. Geotech. Geoenviron. Eng.

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“…For a saturated clay-concrete interface, Di Donna et al showed an increase of the interface shear strength due to heating, which may be explained by thermal consolidation [12]. Yavari et al showed that the temperature effects on the friction angle and adhesion are minor [13][14] and the results of Xiao et al [11] showed a slight decrease of adhesion of the soil-concrete interface when subjected to cooling and negligible effects on the friction angle for unsaturated soil conditions. Xiao et al [15] also pointed out that after 10.5 temperature cycles an increase of the interface shear strength as well as an increase of adhesion (in the case of large heating cycles) was detected for sandy silty clay-concrete interface and it was mostly attributed to water migration due to the temperature changes.…”

Section: Introductionmentioning

confidence: 99%

“…Focusing on the response of the soil-pile interface, Xiao et al, Di Donna et al, and Yavari et al performed direct shear tests to explore the effect of the temperature changes [11][12][13][14] and Xiao et al [15] investigated the effect of temperature cycles on a disturbed natural soilconcrete interface for unsaturated conditions. For a saturated clay-concrete interface, Di Donna et al showed an increase of the interface shear strength due to heating, which may be explained by thermal consolidation [12].…”

Section: Introductionmentioning

confidence: 99%

Influence of thermal cycles on the deformation of soil-pile interface in energy piles

et al. 2019

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Energy piles are double purpose foundation elements used both for transferring loads to the soil and temperature regulation in buildings. The response of the pile-soil interface is influenced by daily and seasonal temperature variations. In order to assess the impact of thermal cycles on the mobilization of shear strength in energy piles, a series of saturated soil-concrete interface direct shear tests were performed in the laboratory for different temperature gradients with a new interface direct shear device adapted for thermomechanical loading. As natural soils are very complex due to a high variability of mineralogy and anisotropy, silica and carbonate sands were chosen in this study. Those sands are considered as the main types of sandy soils commonly met in geotechnics. The experimental campaign is divided in two parts: (i) Concrete-soil direct shear tests at 13°C (constant temperature) to be used as a reference (ii) Concrete-soil direct shear tests after 10 temperature cycles with a gradient ∆T=10°C, under submerged conditions. For these two types of soils, realistic temperature cycles applied between 8 and 18°C cause the overall low contraction of the samples. However the interface friction angles are not significantly modified before and after the temperature cycles. Even if the vertical strains of soils are cumulative along temperature cycles, soil's strains and friction angle changes are relatively negligible for the temperatures and water content tested, which support the low impact of temperature cycles on the deformation of soil concrete foundation under submerged conditions. These experimental results bring new features which will be implemented in numerical models to study the long-term use of energy piles.

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“…Small-scale physical model studies with thermal cycles on energy piles (Kalantidou et al, 2012;Stewart and McCartney, 2014;Yavari et al, 2014Yavari et al, , 2016aWang et al, 2017;Nguyen et al, 2017) have indicated that the thermally induced axial settlement of the pile is reversible for pile head loads corresponding to as low as 20% of the ultimate pile capacity, but becomes irreversible for higher pile head loads closer to the ultimate pile capacity. The field tests conducted by Faizal et al (2018) indicated that the axial and radial thermal responses of an unrestrained energy pile embedded in dense sand followed linear reversible paths for heating and cooling cycles, suggesting that both the pile and the soil did not undergo significant thermally induced deformations.…”

Section: Introductionmentioning

confidence: 99%

Effects of Cyclic Temperature Variations on Thermal Response of an Energy Pile under a Residential Building

Faizal

Bouazza

McCartney

et al. 2019

J. Geotech. Geoenviron. Eng.

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The effects of daily cyclic temperature variations on the thermal response of an energy pile built under a six-level residential building are examined. The axial and radial thermal strains along the length of the pile followed stable, linear reversible paths during daily active heating and cooling cycles corresponding to a pile temperature range of 10 to 23°C (∆T of-8°C to 5°C) around a baseline temperature of 18°C. The stable responses of the thermal strains indicate that plastic deformations did not occur in the pile during the daily cyclic temperature changes coupled with the mechanical load in the pile corresponding to 52% of its estimated ultimate capacity. A complex distribution of axial thermal stresses with depth was observed in the pile with higher stress magnitudes near the pile ends particularly at the end of cooling due to larger temperature changes in the cooling cycle. The magnitudes of radial thermal stresses were considerably smaller than the axial thermal stresses along the length of the pile and are not anticipated to play a significant role in the development of thermo-mechanical loads in the pile. The temperatures over the cross-section of the pile were uniformly distributed at the end of cooling and heating at all depths while the axial thermal stresses had a non-uniform distribution but with magnitudes less than the calculated ultimate capacity of the pile.

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Mechanical behaviour of a small-scale energy pile in saturated clay

Cited by 67 publications

References 38 publications

Axial and Radial Thermal Responses of a Field-Scale Energy Pile under Monotonic and Cyclic Temperature Changes

Axial and Radial Thermal Responses of a Field-Scale Energy Pile under Monotonic and Cyclic Temperature Changes

Influence of thermal cycles on the deformation of soil-pile interface in energy piles

Effects of Cyclic Temperature Variations on Thermal Response of an Energy Pile under a Residential Building

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