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Physical Modeling of Group Energy Pile Behavior under Thermo-Mechnical Loading

Nasehi Heris, Reza | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56710 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Jafarzadeh, Fardin
  7. Abstract:
  8. Energy piles couple the structural support role of conventional piles to the heat exchanger role of shallow geothermal systems for any built environment. So, they are subjected to both mechanical and thermal loads. The use of these piles can be useful in reducing greenhouse gas emissions and reducing fossil fuel consumption. With this in mind, this study is conducted to evaluate the thermomechanical behavior of heat exchanges group piles. For this porpuse, a physical model has been constructed in the Advanced Soil Mechanics Laboratory of the Civil Engineering Department at Sharif University of Technology. In this physical model, four closed-end aluminum pipes with a diameter of 20 mm and a length of 600 mm are used as pile models in the group pile, and each pile is equipped with a U-shaped pipe to circulate water inside the pile. The space between the absorber pipe and the pile is filled with water to have the same temperature throughout the pile. Besides, a water bath is used to control and change the temperature, which is equipped with a water circulation system. In this model, 16 temperature sensors are used, 12 of which are embedded around the pile and inside the soil. Four other sensors are used to measure the temperature of the pile. Also, in this model, 128 strain gauges are used along with the pile on its outer surface; in a way, that strain gauges are installed on four sections in each pile. The sections are 10, 30, 40, and 55 cm apart from the top of the pile. At each section, eight strain gauges are used, 4 of which are used to measure axial strain, and four other strain gauges are used to measure bending strain. Besides, LVDTs are used to measure the head settlement of each pile. In this physical model, the total pressure cells are also used to monitor the vertical and horizontal pressure changes of the soil under the toe pile. Three series of experiments have been conducted to study the mechanical and thermal behavior of heat exchanger group piles. In the first study, only the pile 1 was considered as energy pile and its temperature was adjusted. In the second study, pile 1, 2 were considered as energy piles and in the third experiment piles 1,2 and 3 were assumed to be energy piles. The mechanical loading in all of the experiments were 40 kilograms. The results revealed that in heating cycles, energy piles experienced a settlement and, in the cooling, cycles the energy piles experienced a heave. But, overall, the cycles caused a permanent settlement in the energy piles. Bending moment decreased as the distance from the soil surface increased, while mobilized friction increased as we approach the end of the piles
  9. Keywords:
  10. Energy Pile ; Pile Group ; Physical Modeling ; Geothermal Energy ; Thermomechanical Loading ; Heat Exchanger Pile

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