Numerical study of the response of a group of energy piles under different combinations of thermo-mechanical loads

Donna, Alice Di; Loria, Alessandro F. Rotta; Laloui, Lyesse

doi:10.1016/j.compgeo.2015.11.010

Cited by 129 publications

(49 citation statements)

References 28 publications

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“…For example, Knellwolf et al (2011), McCartney andRosenberg (2011) and Suryatriyastuti et al (2014) used the load transfer (t-z) approach, which includes the effect of thermal expansion and contraction of the pile. The finite-element method has been employed by Laloui et al (2006), Suryatriyastuti et al (2012), Bodas Freitas et al (2013), Dupray et al (2014), Di Donna and Laloui (2015), Rotta Loria et al (2015), Salciarini et al (2015), Bourne-Webb et al (2016) and Di Donna et al (2016), among others. Such studies focus on reproduction of the experimental data and/or investigation of various aspects of the soil-structure interaction, including the effects of the soil's thermal expansion coefficient, pile length, ground surface temperature, thermal loads, as well as cyclic heating and cooling.…”

Section: Introductionmentioning

confidence: 99%

Numerical modelling of thermo-active piles in London Clay

Gawecka

Taborda

Potts

et al. 2017

Proceedings of the Institution of Civil Engineers - Geotechnica

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Thermo-active foundations utilise heat energy stored in the ground to provide a reliable and effective means of space heating and cooling. Previous studies have shown that the effects of temperature changes on their response are highly dependent on their interaction with the surrounding ground. Consequently, it is necessary to consider this interaction and include both the thermal and mechanical behaviour of the ground in design. This paper addresses this issue by performing state-of-the-art finite-element analyses using the Imperial College Finite Element Program, which is capable of simulating the fully coupled thermo-hydro-mechanical behaviour of porous materials. First, the Lambeth College pile test is analysed to demonstrate the capability of the adopted modelling approach to capture the observed response under thermo-mechanical loading. Subsequently, a detailed study is carried out, demonstrating the impact of capturing the fully coupled thermo-hydro-mechanical response of the ground, the use of appropriate boundary conditions and the uncertainty surrounding thermal ground properties. It is demonstrated that the modelling approach has a large impact on the computed results, and therefore potentially on the design of thermo-active piles. Conversely, the effects of thermal conductivity and permeability of the soil are shown not to influence the pile behaviour significantly.

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Section: Introductionmentioning

confidence: 99%

Numerical modelling of thermo-active piles in London Clay

Gawecka

Taborda

Potts

et al. 2017

Proceedings of the Institution of Civil Engineers - Geotechnica

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“…Throughout the design process, these loads were considered as imposed on the uppermost surface of the slab in correspondence with the area delimited by the cross-sectional surface of the underlying piles. This loading situation is considered in this work (as in that presented by Di Donna et al (2016)). The energy piles were equipped with four 24-m-long high-density polyethylene U-loops that are connected in series.…”

Section: The Pile Foundation and Sitementioning

confidence: 99%

“…Mimouni & Laloui (2015) indicated a thickness of the slab of 0·5 m based on the smallest value of height of the cross-section characterising the central zone of this element in plan view. The thickness considered in this work (which corresponds to that proposed by Di Donna et al (2016) and is supposed to be constant over the breadth and length of the slab in the numerical model) is the dimension of the height of the cross-section of the slab at the joint zones with the piles. Because this latter value of height is considered to predominantly characterise the response of the piles over the breadth and length of the slab, it is accounted for in the following analyses.…”

Section: The Pile Foundation and Sitementioning

confidence: 99%

“…Several in situ tests (McCartney & Murphy, 2012;Murphy et al, 2014;Mimouni & Laloui, 2015) and numerical analyses (Di Donna & Laloui, 2014;Jeong et al, 2014;Salciarini et al, 2015;Di Donna et al, 2016;Suryatriyastuti et al, 2016) have recently investigated this problem for energy pile groups. To date, however, knowledge of the development and impact of thermally induced group effects among closely spaced energy piles on their thermo-mechanical behaviour has been limited due to the lack of field data about the exploitation of energy piles that either partially or entirely operate as geothermal heat exchangers for timescales that are typical of practical applications.…”

Section: Introductionmentioning

confidence: 99%

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Thermally induced group effects among energy piles

Loria

2017

Géotechnique

143

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The behaviour of conventional pile groups (e.g. closely spaced) that are subjected to mechanical loads has been shown to be different from the behaviour of single isolated piles. The so-called 'group effects' are responsible for this behaviour and must be considered for an optimal design of pile foundations. In recent years, energy piles have shown potential to work as both structural supports and geothermal heat exchangers, and thus are subjected to both mechanical and thermal loads. An increasing amount of research has investigated the previously unexplored impact of thermal loads on the thermo-mechanical behaviour of energy piles. However, no field data over typical timescales of practical geothermal applications have been available to analyse the development and impact of thermally induced group effects between energy piles (e.g. closely spaced) on their thermo-mechanical behaviour. To investigate this problem, a full-scale in situ test of a group of energy piles and coupled three-dimensional thermomechanical finite-element analyses were performed and are presented in this paper. This work demonstrates that significant thermally induced group effects characterise closely spaced energy piles. Attention must be devoted to these effects throughout the design process (e.g. geotechnical, structural and energy) of energy piles because they play an important role in the serviceability performance of these foundations.

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“…They have also been recently observed in innovative applications of energy piles subjected to both mechanical and thermal loads when serving as structural supports and geothermal heat exchangers for civil structures and infrastructures (e.g. Di Donna et al, 2016;Rotta Loria & Laloui, 2016b).…”

Section: Introductionmentioning

confidence: 99%

The equivalent pier method for energy pile groups

Loria

Laloui

2017

Géotechnique

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This study presents a method for estimating the average vertical displacement of energy pile groups subjected to thermal loads. The method consists of replacing any regular energy pile group with a single equivalent pier of the same length and an equivalent diameter. This equivalent pier is described by material properties that are a homogenisation of those of the piles and the surrounding soil and by a load-displacement relationship of a characteristic energy pile in the group. The load-displacement relationship of the equivalent pier differs from that of a single isolated energy pile because it is modified to account for the group effects. These effects include a greater vertical displacement of the piles subjected to loading in the group compared to the case in which they are isolated, thus involving a more pronounced average group displacement. Comparisons with results obtained through the interaction factor and finite-element methods prove that the proposed approach can accurately estimate the average vertical displacement of energy pile groups. This novel formulation of the equivalent pier method may be used at both preliminary and successive stages of the analysis and design of energy pile groups to assess expediently the thermally induced displacement response of such foundations.

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Numerical study of the response of a group of energy piles under different combinations of thermo-mechanical loads

Cited by 129 publications

References 28 publications

Numerical modelling of thermo-active piles in London Clay

Numerical modelling of thermo-active piles in London Clay

Thermally induced group effects among energy piles

The equivalent pier method for energy pile groups

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