间歇式运行模式下黄土地基中能量桩热-力特性模型试验  

Model tests on thermal-mechanical behavior of energy piles in loess ground under intermittent operation mode

作　　者：曹卫平[1,2] 李清源 赵敏[3] 吴奇兴 李庆 Cao Weiping;Li Qingyuan;Zhao Min;Wu Qixing;Li Qing(School of Civil Engineering,Xi’an University of Architecture&Technology,Xi’an 710055,China;Key Laboratory of Geotechnical and Underground Space Engineering of Shaanxi Province,Xi’an University of Architecture&Technology,Xi’an 710055,China;Xi’an Technological University,Xi’an 710021,China)

机构地区：[1]西安建筑科技大学土木工程学院,陕西西安710055 [2]西安建筑科技大学陕西省岩土与地下空间工程重点实验室,陕西西安710055 [3]西安工业大学,陕西西安710021

出　　处：《土木工程学报》2024年第9期123-134,共12页China Civil Engineering Journal

摘　　要：能量桩是将传统桩基与地源热泵相结合的一种建筑节能新技术。为研究黄土地层中能量桩热交换效率及承载变形特性,了解黄土饱和状态对能量桩热交换效率、桩土温度、桩土沉降及桩身轴力、摩阻力的影响规律,开展间歇式运行模式下黄土处于天然湿密状态及饱和状态的能量桩模型试验。试验采用的黄土为人工配制黄土,模型桩为内置单U形换热管的现浇钢筋混凝土桩。试验结果表明:黄土中能量桩具有较高的热交换效率,黄土饱和时能量桩的热交换效率大于黄土处于天然湿密状态,随着无量纲直径D/L的增大,能量桩的热交换效率增加。不论黄土处于天然湿密状态还是饱和状态,桩顶沉降呈现出棘轮形式并随冷热循环次数增加逐渐增大。热循环、冷循环对能量桩的承载力影响不同,经过每一个完整的冷热循环后,桩的承载力均降低了。该文还建立了计算能量桩热交换效率的新公式,该公式考虑了桩身侧表面积及循环液与初始地温差的影响。Energy pile is a new building energy-saving technology that combines traditional pile foundation with geothermal pump.Model tests,under intermittent running mode,were conducted on energy piles which were embedded in loess ground with two different states of density and moisture,i.e.,the state of natural density and water content and the fully saturated state,in order to study the heat exchange efficiency and bearing deformation behavior of energy pile in loess ground as well as to understand how the saturation of loess affects the heat transfer efficiency,the temperature and settlement of pile and surrounding soil,and the axial force and skin friction of the pile.The loess used in tests is artificially prepared and the model piles are cast-in-place reinforced concrete pile equipped with single U-shape heat pipe exchanger.The test results show that the heat exchange efficiency for energy piles in saturated loess is greater than that in unsaturated loess.The heat exchange efficiency of energy pile increases with the normalized diameter of pile,D/L.A ratcheting pattern for pile head settlement and the increase of the pile settlement with the cycles were observed during cyclic thermal loading regardless of the saturation sate of the surrounding loess.It was also found that the heating and cooling cycles have different effects on the pile capacity depending on the saturation sate of the loess,while the bearing capacity of energy pile decreases after every heating-cooling cycle.In addition,a new approach was proposed to calculate the heat exchange efficiency,which consider the influences of side surface area of pile shaft and the initial temperature difference between heat carrier fluid and ground.

关 键 词：能量桩 承载变形特性 冷热循环 黄土 模型试验 

分 类 号：TU473[建筑科学—结构工程] TU43[建筑科学—土工工程]