Behaviour of a group of energy piles

Mimouni, Thomas; Laloui, Lyesse

doi:10.1139/cgj-2014-0403

Cited by 157 publications

(66 citation statements)

References 13 publications

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“…The fullscale field experiments reported by Brandl (2006), Laloui et al (2006), Bourne-Webb et al (2009), Akrouch et al (2014), Mimouni and Laloui (2015), Murphy et al (2014) and Wang et al (2015), as well as experimental set-ups by McCartney and Rosenberg (2011), Kalantidou et al (2012), Stewart and McCartney (2013), Ng et al (2014) and Yavari et al (2014a) have provided an invaluable insight into the behaviour of thermo-active piles. Moreover, the results of the first field tests (Bourne-Webb et al, 2009;Brandl, 2006;Laloui et al, 2006) have led to the development of a simplified descriptive framework for thermo-mechanical pile response (Amatya et al, 2012;Bourne-Webb et al, 2013).…”

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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“…The variation of the latter parameter was based on the determination (without accounting for capacitive effects) of an effective thermal conductivity for the soil deposit of λ eff = 2·78 W/(m°C). This average value of effective thermal conductivity was determined experimentally with reference to the soil around the thermally active portion of the operating energy pile EP1 and is slightly lower than the value of λ eff = 3·1 W/(m°C) suggested by Mimouni & Laloui (2015) that was considered by Di Donna et al (2016). Knowledge of λ eff , together with the porosity values of all of the soil layers, allowed calculation of the thermal conductivity of solid particles of the various layers that were subsequently modified based on a comparison with the experimental results for best capturing the thermal behaviour of the foundation.…”

Section: Classification Of the Numerical Simulations And Materials Promentioning

confidence: 60%

“…1(b)) below a heavily reinforced 0·9 m-thick slab. 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.…”

Section: The Pile Foundation and Sitementioning

confidence: 99%

“…the pipe configuration, the mass flow rate of the fluid circulating in the pipes and the fluid mixture composition), and (b) the thermal and hydraulic properties of the foundation. These interactions were not observed by Mimouni & Laloui (2015) because of the short duration of their tests, but are considered to be important for the analysis and design (e.g. geotechnical, structural and energy) of these foundations.…”

Section: Key Aspects Governing the Behaviour Of Energy Pile Groupsmentioning

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%

See 2 more Smart Citations

Thermally induced group effects among energy piles

Loria

2017

Géotechnique

144

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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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Coupled consolidation and heat flow analysis of layered soils surrounding cylindrical heat sources using a precise integration technique

Wang

Zhu

Chen

et al. 2019

Num Anal Meth Geomechanics

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Summary The engineering applications of energy piles, geological radioactive waste disposals, and mining wells of geothermal and petroleum are usually associated with strong coupled behaviour of consolidation and heat flow. This paper aims to present an efficient precise integration technique (PIT) for the analysis of such behaviour within layered saturated soils surrounding cylindrical heat sources (ie, with a cross section as a point, ring, or disc). Each soil layer, together with its embedded part of heat source, is divided into 2N layer elements with equal thickness. Then any pair of adjacent two layer elements are merged into a heat source on the interface. With the aid of Taylor series expansion and recurrence formula for adjacent layer elements combination, such problems can be solved by means of an improved PIT. Typical examples are performed to examine the effects of heat source type and soils layered properties on the coupled consolidation and heat flow responses. The elevation of the clay surface increases with time because of thermal expansion and reaches a peak value before showing a tendency of getting stabilised because of the dissipation of pore pressure becoming dominant. Such a peak cannot be achieved in sand case because of no accumulation of pore pressure. The influencing area of the heat source was found to be limited to near the source. These quantitative results serve as good verification of the presented technique, which proves to be remarkably efficient and several orders more accurate than traditional numerical techniques in that it ideally reaches the accuracy limit of the hardware of the computers used.

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Behaviour of a group of energy piles

Cited by 157 publications

References 13 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

Coupled consolidation and heat flow analysis of layered soils surrounding cylindrical heat sources using a precise integration technique

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