能源桩桩身横向变形试验研究

Experimental study on lateral deformation characteristics of energy piles

关于地源热泵系统(GSHP)运行条件下的能源桩竖向变形特征研究已经取得了大量的成果,然而,目前对能源桩横向变形特征如何影响桩体摩阻力和传热特性的认识还不够充分。在模拟能源桩实际运行工况的条件下进行室内试验,测试了温度循环条件下桩身-岩土体接触界面的变形特征。试验结果表明:温度变化会使桩-土接触界面产生变形,其变形量足以使桩侧摩阻力发生变化,进而改变桩土接触条件并影响能源桩的传热效率。这些研究结论与现场桩身结构响应测试结果较为吻合:温度变化时能源桩桩身侧壁会产生横向的热胀冷缩,随着桩身横向变形,桩侧壁会产生桩侧摩阻力,其大小取决于桩壁深度和温差。

Vertical deformation characteristics of energy pile caused by ground source heat pump system(GSHP)operation have been studied widely.However,there is insufficient understanding on the influence of lateral deformation on friction and heat transfer of energy pile.In this paper,laboratory tests were carried out to monitor the deformation characteristics of sandstone-concrete interface under the condition of temperature cycling.The results showed that the temperature change would cause the deformation of the interface between the energy pile and the rock,which was enough to change the side resistance of the pile,and then changed the sandstone-concrete interface condition,thus affecting the heat transfer efficiency of energy pile.This was in agreement with in-situ test results.It was found that the pile body showed lateral heat-expansion and cold-contraction.Pile side friction would generate on the side wall of the pile due to lateral deformation,which varied with the depth of the pile wall and temperature difference.