MODEL TEST ON THERMO-MECHANICAL CHARACTERISTICS AND BEARING DEFORMATION BEHAVIOR OF ENERGY PILE INLOESS FOUNDATION

Cao Weiping; Li Qing; Li Qingyuan

doi:10.19912/j.0254-0096.tynxb.2022-0812

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Acta Energiae Solaris Sinica ›› 2023, Vol. 44 ›› Issue (4) : 539-546. DOI: 10.19912/j.0254-0096.tynxb.2022-0812

MODEL TEST ON THERMO-MECHANICAL CHARACTERISTICS AND BEARING DEFORMATION BEHAVIOR OF ENERGY PILE INLOESS FOUNDATION

Cao Weiping, Li Qing, Li Qingyuan

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Abstract

Energy piles utilize shallow geothermal energy by exchanging heat with surrounding soils through built-in circulating pipe. Model tests were conducted to investigate the behavior of energy pile embedded in loess soils during 4 entire heating-cooling cycles under two conditions, i.e., the energy pile only experienced heating-cooling cycles and the energy pile experienced loading throughout the heating-cooling cycles. The variation of the temperature of the pile and surrounding soils, the settlement of the soil surface and the pile as well as the pile head load and its internal force were recorded. Furthermore, the load-bearing deformation characteristics and thermo-mechanical characteristics of energy pile with single U-shaped heat exchanger were analyzed. The test results indicated that the pile heat transfer efficiency gradually decreases to a stable state with the development of cycling. The temperature in the energy pile shaft in loess soils decreases with the depth and the cooling-heating cycles will cause accumulation of settlement of the pile. Compared with the energy pile only experiencing heating-cooling cycles, the energy pile experiencing loading throughout the heating-cooling cycles will result in a greater accumulative settlement of pile and a smaller settlement in soil surface as well as a greater range of soils influenced surrounding the pile. For the two above conditions, the maximum superimposed stress will occur near the middle of the pile shaft after the cooling-heating cycles are stable. Heating process will induce negative, positive skin friction on the upper and lower pile shaft, respectively. While cooling process will cause opposite skin friction on the upper and lower pile shaft.

Key words

geothermal energy / energy pile / loess foundation / model test / cooling-heating cycles / thermo-mechanical coupling

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Cao Weiping, Li Qing, Li Qingyuan. MODEL TEST ON THERMO-MECHANICAL CHARACTERISTICS AND BEARING DEFORMATION BEHAVIOR OF ENERGY PILE INLOESS FOUNDATION[J]. Acta Energiae Solaris Sinica. 2023, 44(4): 539-546 https://doi.org/10.19912/j.0254-0096.tynxb.2022-0812

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