热力耦合作用下新型相变混凝土能量桩传热机制及承载性能研究

The energy consumption of urban heating accounts for about 11.5% of the total energy consumption in China. At present, commonly used centralized heat-supply is based on burning fossil fuels for example coal, which exacerbates air pollution in region with heating provision. Shallow geothermal energy at shallow depths is a kind of renewable energy, The utilization of shallow geothermal based on energy pile can effectively solve or alleviate the building energy consumption problem. However, temperature stress caused by insufficient heat exchange affected the bearing capacity of energy pile, seriously which limits its popularization and use. To solve the above problems, phase-change energy storage technology, optical fiber sensing technology, geotechnical centrifuge technology, and finite element method are fused to test the hydration process and physical and mechanical properties of phase-change concrete, optimize the proportion of phase-change concrete, improve the physical and mechanical properties of energy pile, develop high precision phase-change concrete-soil interface shear test system, study on the evolution law of shear strength of phase-change concrete-soil interface under thermo-mechanical coupling condition, construct a thermo-mechanical coupled finite element model to investigate the thermal tuning and allocation mechanism of phase-change concrete pile, improve the thermal conversion efficiency, reveal the bearing mechanism of phase-change energy concrete pile by using laboratory model experiments and finite element numerical simulation. The research results of this project will provide fundamental data and theoretical support for the thermo-mechanical coupling effect study of pile engineering in complex environments.

我国城镇建筑采暖能耗约占全国能源消费总量的11.5%，目前最主要的集中采暖方式仍是燃烧煤炭等化石能源，这加剧了采暖区的大气污染问题。浅层地热是来自地表以下的可再生能源，基于能量桩的浅层地热利用可以有效的解决或者缓解建筑能耗过高问题，然而目前由热交换不充分引起的温度应力严重影响了能量桩的承载性能，限制了其推广使用。针对上述问题，本项目融合相变储能技术、光纤传感技术、土工离心机技术和有限元计算方法，开展相变混凝土水化过程和物理力学性能测试，优化相变混凝土配比，改善能量桩物理力学性能；研发高精度相变混凝土-土界面剪切实验系统，研究热力耦合作用下相变混凝土-土界面剪切强度演变规律；建立热力耦合有限元模型，探明相变混凝土能量桩热调谐及配置机制，提高热转化效率；通过模型实验和有限元数值模拟揭示相变混凝土能量桩承载机理。该项目研究成果为复杂环境中桩基工程的热力耦合效应研究提供强有力的基础数据和理论支持。

能量桩是一种兼具换热和承载复合功能的建筑节能技术，能够有效缓解建筑能耗过高问题。然而，普通混凝土能量桩存在换热效率低、热力耦合作用下长期承载性能有待改善等问题，阻碍了能量桩技术的进一步发展和应用。针对上述问题，本项目提出了相变混凝土能量桩解决方案，首先开展早期水化性能和热物理性能测试实验，优化相变混凝土配比；研究了桩体热物理力学性质对相变混凝土能量桩换热性能的影响，提出了适用于热力耦合设计的代表性温度变化计算模型和能量桩传热性能优化解析模型，以提高能量桩的热能转化效率。此外，融合光纤光栅和智能温控等新型传感技术，搭建了冷热循环精确可调的能量桩桩-土界面接触特性监测系统，研究了循环温度荷载作用下桩-土界面剪切强度和能量桩承载性能发展规律，提出了能量桩承载性能荷载传递模型、基于马尔科夫链蒙特卡洛模拟的能量桩单桩优化设计方法和基于人工神经网络的能量桩长周期位移发展评估模型，实现了改善能量桩长期承载性能的目的。项目研究成果为循环温度作用下能量桩换热性能优化和长期热力耦合响应机理研究提供了强有力的基础数据和理论支撑。