Centrifuge modelling of displacement and replacement energy piles constructed in saturated sand: a comparative study

Ng, Charles Wang Wai; Gunawan, Anthony; Shi, Chao; Ma, Qijie; Liu, Hanlong

doi:10.1680/jgele.15.00119

Cited by 51 publications

(13 citation statements)

References 13 publications

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“…In addition to these mechanical actions, thermal loading will occur upon repeated heating-cooling cycles. The complex thermomechanical loading conditions and the associated interaction between the pile and the surrounding soil could substantially affect the capacity (e.g., Goode and McCartney, 2015) and serviceability (e.g., Ng et al, 2016a) of the soil-pile system.…”

Section: Introductionmentioning

confidence: 99%

Thermally induced ratcheting of a thermo-active reinforced concrete pile in sand under sustained lateral load

2023

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Thermally-induced ratcheting of a thermo-active pile is the accumulation of net and irreversible pile head displacement upon heating–cooling cycles. Although this kind of phenomenon has been observed in vertically-loaded piles in sand, it is unknown whether this exists in laterally-loaded cases, and also what underlying mechanisms occur under the thermomechanical flexural soil-pile interaction. This study presents a series of centrifuge tests and finite-element simulations of the thermomechanical behaviour of a laterally-loaded thermo-active pile in sand. A new model reinforced concrete (RC) was used in the centrifuge tests to realistically mimic the thermal and mechanical properties of a prototype RC pile. Ratcheting was evident in laterally-loaded piles and its extent was more significant when the working horizontal load is higher. The ratcheting phenomenon was attributed to the accumulation of soil plastic strain due to the cyclic mechanical loading induced by pile thermal horizontal expansion and contraction, soil dilation upon soil-pile interface shearing, and creep. The additional bending moment induced by the thermal action did not induce yielding within the pile. A subsequent numerical sensitivity study suggested that ignoring the softening behaviour of the sand would lead to underestimation of the magnitude of the accumulative thermally-induced pile head lateral displacement.

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Section: Introductionmentioning

confidence: 99%

Thermally induced ratcheting of a thermo-active reinforced concrete pile in sand under sustained lateral load

2023

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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%

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.

107

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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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“…The results indicate that the radial thermal effects are significantly lower compared to the thermal axial effects at all depths of the energy pile. The radial thermal effects are lower than the axial thermal effects possibly due to the small magnitude of the ratio of the pile diameter to the pile length (i.e., 0.06) as well as the particular construction effects associated with bored cast-in-place piles where the density of the soil on the borehole wall is not significantly modified compared to driven piles (Ng et al 2016).…”

Section: Thermal Responses To Change In Pile Temperaturesmentioning

confidence: 99%

Axial and radial thermal responses of energy pile under six storey residential building

et al. 2019

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The axial and radial thermal responses of a cast-in-place energy pile, 10 m long and 0.6 m in diameter, installed in unsaturated sand under a six storey building are examined during a heating–cooling cycle. The instrumentation in the pile was configured to compare radial and axial thermal responses at the same elevations and to evaluate the temperature and axial thermal stress distribution across the cross-sectional area of the pile. The magnitudes of the axial thermal strains were more constrained than the radial thermal strains at all depths, leading to the development of axial and radial thermal stresses of up to –4.5 and –0.015 MPa, respectively, for a change in average pile temperature of 24.1 °C. The magnitudes of the radial thermal stresses with changes in pile temperature were significantly lower than the axial thermal stresses at all depths of the pile, indicating that the radial thermal expansion had negligible effects on the development of axial thermal strains and stresses. The temperature distribution over the cross section of the pile showed low variations at all depths, indicating that it would be justified to consider a uniform temperature distribution at least in piles of similar dimensions and with even heat exchanger layouts.

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Centrifuge modelling of displacement and replacement energy piles constructed in saturated sand: a comparative study

Cited by 51 publications

References 13 publications

Thermally induced ratcheting of a thermo-active reinforced concrete pile in sand under sustained lateral load

Thermally induced ratcheting of a thermo-active reinforced concrete pile in sand under sustained lateral load

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

Axial and radial thermal responses of energy pile under six storey residential building

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