Centrifuge modelling of heating effects on energy pile performance in saturated sand
Bibliographic record
Abstract
The operation of energy piles in summer can expel excess heat of the buildings into the ground by the use of a heat pump. Despite having been implemented for decades, the design of energy piles still relies heavily on empiricism, as there is limited understanding about heating effects on pile capacity. A series of centrifuge model tests on aluminum energy piles in medium dense saturated sand is reported in this study to investigate heating effects on the settlement patterns as well as capacities of single piles. In total, four in-flight pile load tests under three different temperatures, namely 22, 37, and 52 °C, and different loading sequences were carried out. Variations of pile capacity were interpreted with the help of a nonlinear elastic analysis. The test results show that after heating at zero applied axial load, toe resistance of the pile was mobilized as a result of constrained downward thermal expansion of the pile. Heating to a higher temperature caused the neutral plane to shift towards the pile toe due to a larger degree of mobilization of end-bearing resistance. It is also found that for a pile under a maintained working load, the pile head heaved initially by 1.4%D (D, pile diameter) when the temperature increased by 30 °C, but it gradually settled to 0.8%D after 4 months of continuous heating at the constant temperature. The post-pile settlement is believed to be caused by thermal contraction of sand. Subsequent pile load tests show that pile capacities increased by 13% and 30% with incremental temperatures of 15 and 30 °C, respectively. With an increasing temperature, shaft resistance increased but at a reducing rate. At a higher elevated temperature, toe resistance increased more rapidly than shaft resistance due to a larger downward expansion of the pile. For simplicity, earth pressure coefficients with values of 1.1K 0 and 1.3K 0 were found to be suitable for estimating the capacities of aluminum model piles with temperature increments of 15 and 30 °C, respectively.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".