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Field Test on Heat Transfer Efficiency and Thermal Mechanical Response of Energy Pile Foundation with Cap Under Embedded Depth(PDF)


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Field Test on Heat Transfer Efficiency and Thermal Mechanical Response of Energy Pile Foundation with Cap Under Embedded Depth
CHEN Yu1 KONG Gang-qiang12 MENG Yong-dong1 WANG Le-hua1 LIU Hong-cheng1
(1. Key Laboratory of Geological Hazards on Three Gorges Reservoir Area of Ministry of Education, China Three Gorges University, Yichang 443002, Hubei, China; 2. Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University, Nanjing 210098, Jiangsu, China)
energy pile embedded depth of foundation heat transfer efficiency thermal mechanical response field test
Based on the low-cap 2×2 pile foundation under embedded depth condition, heat exchange tubes were tied on the bored pile reinforcement cage to form energy piles, and vibrating wire strain gauges/thermometers were arranged to test the temperature and thermal strain of the pile body. The thermal mechanical response characteristic test of a single energy pile operation to the adjacent pile foundation and cap under the constant input water temperature(35 ℃)was carried out; the inlet/outlet water temperature changing with time and the thermal strain of the pile body were measured. The heat transfer efficiency of a single energy pile and its thermal mechanical response characteristics of the cap and adjacent piles were compared and analyzed under the condition of with/without embedded depth. The results show that the heat transfer efficiency under the 3 m depth is 2.65 kW, which is about 68% higher than that of no embedded depth in this field test condition, reflecting the existence of a certain heat retention capacity of the overlying backfill. Under the condition of with/without embedded depth, the maximum thermal stress of the pile body appears in the middle of the pile body and the pile top respectively, which are 1.66 MPa and 2.14 MPa. During the heating process, the pile tip resistance increases first and then gradually decreases to a stable value. After heating for 24 h, it reaches a maximum value of about 20 kPa, which is consistent with the change trend of the inlet/outlet temperature difference. Under the condition of with/without embedded depth, the cap shows slightly different deformations in the heating conditions, and certain consideration should be given to the design of the energy pile structure with the cap. The maximum thermally induced stress values of the cap with/without embedded depth are 0.65 MPa and 2.34 MPa respectively, and the corresponding maximum temperature rise is 3.6 ℃ and 11.0 ℃.


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Last Update: 2021-09-01