Thermomechanical Behavior of Energy Piles with Different Roughness Values in Unsaturated Soil
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 150, Issue 5
Abstract
Energy piles are often partially or fully embedded in unsaturated soils, particularly in arid and semiarid regions; however, suction effects on their thermomechanical behavior have not been fully understood. In this study, a series of physical modeling tests were carried out to investigate the behavior of energy piles in unsaturated soils. The soil used for testing is completely decomposed granite, which is a type of clayey sand sampled from Hong Kong. Five constant-temperature pile load tests and three constant-load heating and cooling tests were conducted under different conditions of pile surface roughness and initial soil suction. It is observed that the ultimate capacity of the energy pile () increases as the initial suction increases from 0 to 90 kPa, the pile roughness increases from 0.05 to 1, and the temperature increases from 10°C to 21°C. Moreover, the effects of roughness are more significant in unsaturated conditions than in saturated states. A suction increment can increase both shaft and toe resistance, while temperature and roughness mainly affect the shaft resistance. During cyclic heating and cooling, suction and roughness increment reduces the irreversible pile head settlement due to the increment of shaft resistance. Furthermore, the irreversible pile head settlement is greatly affected by vertical load. When the working load is relatively small (smaller than in this study), the settlement increases with the number of thermal cycles but at a decreasing rate for both saturated and unsaturated conditions, and finally reaches a stable state. When the working load is relatively high ( in this study), the response of the pile does not reach a stable state in saturated conditions even after five thermal cycles. These observations should be treated with caution because they may be specific and only applicable to the case of no overburden pressure. Exercising caution is crucial when interpreting these observations, particularly at a quantitative level, because they may be limited to the test soil and the low stress level utilized in the physical model tests.
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Data Availability Statement
All data, models, and code generated or used during the study appear in the published paper.
Acknowledgments
The Shenzhen Science and Technology Innovation Commission supports this work through research grant 2022N040. The authors also thank the HKSAR Research Grants Council (RGC) for providing financial support through the grants 15200120 and the RGC Direct Allocation Grant P0038211. The third author acknowledges the financial support from the Fifth Round (2023) of the ASPIRE League Partnership Seed Fund, and the AcRF regular Tier 1 Grant (Project No. RG69/23) from the Ministry of Education, Singapore.
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Journal of Geotechnical and Geoenvironmental Engineering
Volume 150 • Issue 5 • May 2024
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© 2024 American Society of Civil Engineers.
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Received: Mar 6, 2023
Accepted: Dec 27, 2023
Published online: Mar 14, 2024
Published in print: May 1, 2024
Discussion open until: Aug 14, 2024
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