49 / 2021-10-08 20:57:22

非饱和黏土地层相变能源桩冷热循环热响应试验研究

相变能源桩；冷热循环；不均匀温度；非饱和黏土；固结沉降

采用钢球封装相变材料替换混凝土中粗骨料能够增加桩体的能量密度、提高换热量，从而减小热交换所需的地下空间资源。本研究通过模型试验对非饱和黏土中的普通混凝土和相变储能混凝土能源桩进行冷热循环加载，对比研究其热响应特性和对桩周土体的影响。结果表明：相变桩在冷热循环的热交换过程中桩体对于土体温度的影响范围约为1.5倍桩径，相变桩的换热管进出口温度变化大于普通桩，表明相变桩热交换效率高于普通桩；相变桩与普通桩在制热循环中的温差小于制冷时的温差，说明制冷加载在相同循环工况下的换热效率要大于制热加载；在制冷循环中相变材料的加入导致桩内竖向和横截面温度的不均匀性。另外，在温度循环作用下正常固结非饱和黏土地基产生明显的固结排水，发生不可恢复的沉降变形。



Using steel ball to encapsulate phase change material (PCM) and replace coarse aggregate in concrete can improve the energy density and heat transfer of the pile; thereby reduce the underground space required for heat exchange. In this study, cooling-heating circulating load was performed on the ordinary concrete energy pile and PCM energy pile placed in a model box containing unsaturated clay to study the thermal response of the piles and influence to the surrounding soil. The results show that the temperature influence range of phase change pile in soil is about 1.5 times of pile diameter in the cooling-heating exchange process, and the difference between the inlet and outlet of the PCM pile is larger than that of the ordinary concrete pile, indicating a large amount of heat transfer. The temperature difference of the PCM pile and the ordinary pile in the heating process is less than that in the cooling process, indicating that the heat transfer efficiency of the cooling mode is larger than that of the heating mode under the same circulating condition. The addition of PCM in the cooling process leads to the uneven distribution of temperature in the vertical direction and cross section of the pile. In addition, obvious consolidation and drainage was observed under the action of temperature cycle, resulting in irreversible settlement of unsaturated clay.