In recent years, energy piles have been widely used in the collection of shallow geothermal energy. However, the engineering characteristics of the soil and the mechanical behaviour of the pile are affected by temperature, particularly in clay. To explore the influence of heating–cooling cycles on the thermo-mechanical response of an energy pile in saturated clay, a laboratory model test was designed. The energy pile in saturated clay was subjected to ten heating–cooling cycles. A fibre Bragg grating (FBG) system was adopted to monitor the pile strain. Meanwhile, pile and soil temperature, pore water pressure and pile top displacement data were collected using a dynamic acquisition instrument. The results show that FBG sensors can achieve good results in measuring the axial strain of a pile. The distribution and transmission of thermally induced axial force and stress are affected by soil properties and pile constraints. Temperature cycling will lead to the thermal consolidation of saturated clay, improving the bearing performance of energy piles, and to an irreversible settlement of the energy pile.

中文翻译：

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饱和粘土中能量桩的热力响应研究

近年来，能量桩在浅层地热能采集中得到广泛应用。然而，土壤的工程特性和桩的力学性能受温度影响，特别是在粘土中。为了探讨加热-冷却循环对饱和粘土中能量桩热机械响应的影响，设计了实验室模型试验。饱和粘土中的能量堆经历了十次加热-冷却循环。采用光纤布拉格光栅（FBG）系统监测桩应变。同时，采用动态采集仪采集桩土温度、孔隙水压力和桩顶位移数据。结果表明，光纤光栅传感器在测量桩的轴向应变方面取得了较好的效果。热致轴向力和应力的分布和传递受土壤特性和桩约束的影响。温度循环将导致饱和粘土的热固结，提高能量桩的承载性能，并导致能量桩的不可逆沉降。