Effects of the pile buried pipe parameters on the thermal-mechanical coupling characteristics of energy pile under the groundwater seepage
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摘要:
为获得地下水渗流作用下桩埋管参数对能量桩热-力耦合特性的影响，建立了不同埋管参数的能量桩数值模型，分析了桩埋管数量、埋管布置形式、埋管管径对单位桩深换热量、日换热量、桩截面平均温升、桩身位移增量及桩身附加温度荷载的影响。结果表明：增加埋管数量可以增大能量桩换热量，但也会加剧桩内不同埋管间的热干扰，导致换热性能下降及桩身位移和附加温度荷载的增加；渗流下桩埋管的布置形式对其换热性能有显著影响，而对桩的力学特性影响较小，且渗流速度越大，2种布置形式对应的能量桩换热量差异逐渐增加，桩顶位移增量与桩身附加温度荷载逐渐减少；增加埋管管径可以提高能量桩的换热量，但也会加大桩身和桩周土壤温升，导致桩身位移和附加温度荷载增大。研究结论对于渗流作用下能量桩的优化设计与高效运行具有一定的指导意义。
Abstract:In order to examine the influences of buried pipe parameters on the thermal-mechanical coupling characteristics of energy piles under the groundwater seepage, the numerical models of energy piles with different buried pipe parameters are established. The influences of the buried pipe number, layout of buried pipe, and diameter of buried pipe on the heat exchange rate per pile depth, daily heat exchange amount, pile body average temperature rises, displacement increment, and additional temperature load are investigated. The results show that the increasing number of buried pipes can improve the heat transfer of energy pile, but also increase the thermal interference between different buried pipes in the pile, resulting in the decrease of heat transfer performance and the increase of pile displacement and additional temperature load. Under the groundwater seepage, the layout of buried pipes has a significant effect on the heat transfer performance, but has little effect on the mechanical properties of the pile. Moreover, with the increasing seepage velocity, the difference of heat transfer rates of the energy piles corresponding to two layouts increases gradually, and the pile top displacement increment and the pile additional temperature load decrease gradually. The increasing diameter of buried pipe can improve the heat transfer of energy pile, but it will also increase the temperature rise of the pile and the soil around the pile, leading to the increase of pile displacement and additional temperature load. The research results can provide guidance for the optimal design and efficient operation of energy pile under seepage action.
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表 1 模拟计算条件
Table 1. Calculated conditions for simulation
参数 数值 U型管内/外径/mm 25/32 U型管导热系数/（W·m−1·K−1） 0.48 U型管密度/（kg·m−3） 1200 U型管比热容/（J·kg−1·K−1） 2300 混凝土密度/（kg·m−3） 2500 混凝土导热系数/（W·m−1·K−1） 2.3 混凝土比热容/（J·kg−1·K−1） 960 土壤固体成分密度/（kg·m−3） 1800 土壤固体成分比热容/（J·kg−1·K−1） 1600 土壤固体成分导热系数/（W·m−1·K−1） 1.7 土壤孔隙率 0.4 循环流体密度/（kg·m−3） 1000 循环流体导热系数/（W·m−1·K−1） 0.67 循环流体比热容/（J·kg−1·K−1） 4216 土壤压缩模量/MPa 35 土壤泊松比 0.3 土壤黏聚力/kPa 20 土壤内摩擦角/（°） 30 混凝土压缩模量/MPa 30000 混凝土泊松比 0.2 
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表 2 不同桩埋管布置形式下能量桩的力学特性
Table 2. Mechanical properties of energy pile for different buried pipe layouts
桩埋管形式 布置形式 桩顶位移增量/mm 最大附加温度荷载/kN 单U 布置一 0.75 53.3 布置二 0.74 51.9 双U 布置一 0.95 64.7 布置二 0.97 65.6
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