Effects of Energy Loops on the Geotechnical Performance of Geothermal Energy Piles-PPT Presentation

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The study investigates how geothermal energy loops affect the load capacity and settlement of geothermal energy piles (GEPs). Because relevant field data and laboratory tests were unavailable, the author analysed 60 hypothetical piles using PLAXIS 3D under compression loading. The models varied pile dimensions and the number of high-density polyethylene (HDPE) tubes, with every pile assumed to be installed in dry sand.<br /><br />The soil was represented using a drained Mohr–Coulomb model, and the concrete piles were modelled as elastic structural elements. PLAXIS could not model the tubes inside a hollow pile, so they were represented as structures attached to the pile’s interface. This modelling constraint is important when interpreting the results.<br /><br />The simulations indicate that the effect of energy loops is not uniform: pile capacity depends on how many tubes are installed. For a typical 2 m diameter pile, 3–4 tubes increased computed capacity by approximately 30–75%, potentially because they reinforced the surrounding soil. In contrast, 11 tubes reduced capacity by as much as 70%, possibly because the crowded tubes increased soil compressibility and reduced its strength.<br /><br />Computed settlements at ultimate resistance were close to 10% of the pile diameter, consistent with observed pile-loading behaviour. The modelled capacities of piles without tubes also agreed with estimates from standard soil-mechanics methods, lending some support to the modelling approach.<br /><br />The author concludes that energy loops can significantly influence GEP performance, but their effects are complex and depend on their number and interaction with the pile and soil. Instrumented pile testing is needed to validate the numerical findings.

Keywords

geothermal energy piles

load capacity

settlement

PLAXIS 3D

HDPE tubes

compression loading

dry sand

Mohr-Coulomb model

pile performance

numerical simulation