Very limited information is available regarding the impact of heating and cooling processes on the geotechnical performance of piled foundations incorporating pipe loops for ground-source heat-pump systems (so-called energy piles). A pile-loading test that incorporated temperature cycles while under an extended period of maintained loading was undertaken to investigate the behaviour of an energy pile installed in London Clay. Testing was carried out over a period of about seven weeks, with conventional loading tests carried out either side of an extended loading test with thermal cycles. Using an optical fibre sensor system, and other more conventional instrumentation, temperature and strain profiles were observed in the test pile, an adjacent bore-hole, two of the anchor piles, and the heat sink pile. Details of load and movement at the pile head, of ambient air temperature and of the input/output temperature of fluid within the heating system were also recorded. Thermodynamic behaviour observed during t...

Energy pile test at Lambeth College, London: geotechnical and thermodynamic aspects of pile response to heat cycles

Experimental data from different testing methodologies on different compacted clayey soils, with dominant bimodal pore size distribution, are presented and analysed, to provide a comprehensive picture of the evolution of the aggregated fabric along hydraulic and mechanical paths. Fabric changes are analysed both from the porous network viewpoint, by means of careful mercury intrusion porosimetry investigation, and from the soil skeleton viewpoint, by quantifying swelling and shrinkage of the aggregates in an environmental scanning electron microscopy study. The consequences of the aggregated fabric evolution on the water retention properties of compacted soils are analysed and discussed. A new model for water retention domain is proposed, which introduces a dependence of the intra-aggregate pore volume on water content. The model succeeds in tracking correctly the evolution of the hydraulic state of the different soils investigated along generalised hydromechanical paths. The proposed approach brings to l...

An insight into the water retention properties of compacted clayey soils

Energy piles are an effective and economic means of using geothermal energy resources for heating and cooling buildings, contributing to legislative requirements for renewable energy in new construction. While such piles have been used for around 25 years with no apparent detrimental effect, there is limited understanding of their thermo-mechanical behaviour. This paper synthesises the results from three published field studies and illustrates some of the engineering behaviour of such piles during heating and cooling. Simplified load transfer mechanisms for a single pile subjected to pure thermal loadings (i.e. without mechanical load) and combined thermo-mechanical loadings have been developed and are used to interpret the field data with regard to change in axial stress and shaft friction during heating and cooling. The effect of end restraint and ground conditions on the thermo-mechanical response of energy piles is discussed. Values of change in axial stress and mobilised shaft friction due to thermal...

Thermo-mechanical Behaviour of Energy Piles

A new model and analytical solutions for borehole and pile ground heat exchangers

Field performance of an energy pile system for space heating

Note: Sols Reference LMS-ARTICLE-2006-008doi:10.1002/nag.499View record in Web of Science Record created on 2006-11-09, modified on 2017-11-27

Experimental and numerical investigations of the behaviour of a heat exchanger pile

Note: Sols Reference LMS-CHAPTER-2005-001 Record created on 2006-11-09, modified on 2017-11-27

Advances in modelling hysteretic water retention curve in deformable soils

Reference EPFL-CHAPTER-149859 URL: http://www.iste.co.uk/index.php?f=x&ACTION=View&id=337 Record created on 2010-07-05, modified on 2016-08-08

Mathieu Nuth

Papers

Experimental and numerical investigations of the behaviour of a heat exchanger pile

Experimental and numerical investigations of the behaviour of a heat exchanger pile

Advances in modelling hysteretic water retention curve in deformable soils

Mechanics of Unsaturated Soils

Mechanics of unsaturated soils