中文摘要：

针对地下换热管0℃以下低温运行工况，开展土壤冻胀挤压换热管变形的实验研究．本实验以u型换热管为例，基于变温运行模式，应用冻结锋面追踪和应变测试手段，研究冻结区发展和管截面变形特性，以及换热管初始变形对其冻胀变形的影响．研究表明，土壤冻结区不均衡发展，发展速度逐渐降低；受其影响，管截面呈现椭圆化变形，变形程度随冻结区发展而不断增大，且增大速度逐渐降低；初始变形可使换热管在冻胀过程中变形程度增加．

英文摘要：

Experimental research was conducted on the condition of ground heat exchange pipe working below 0℃, to investigate pipe deformation due to soil frost heave. This experiment took the U-pipe as an example, on the basis of temperature change mode, to study the characteristics of soil freezing area development and pipe＇s cross-section deformation by means of freezing front tracking and strains measurement. Meanwhile, the influence of pipe＇s initial deformation in the course of frost heave was analysed. The results show that the soil freezing area develops asymmetrically, and its development speed decreases manifests ovalisation under the effect of asymmetrical gradually. The pipe＇s cross-section freezing deformation increases with the expansion of freezing area, and its gradually. The pipe＇s initial deformation can make the subsequent course of frost heave. area. The degree of pipe increasing speed decreases deformation increase in the