中文摘要：

以地源热泵技术在农业节能领域中的应用为研究背景,针对地下换热管土结构冻胀变形问题开展数值模拟研究,基于孔隙增长率函数、冻土本构方程、含水量方程和相变传热理论建立数值模型,并结合试验验证该模型的有效性。利用模型对冻胀过程中岩土应力和管体变形特性进行分析,并考察管体降温速率（0.1、0.2、0.3℃/h）对上述2方面的影响。结果表明,岩土冻胀应力和管体变形程度均随冻结范围增大而增大,当冻结直径达到365 mm时,进水管流通面积减小约3.5%,出水管流通面积减小可超过4%,可见出水管的变形更为明显;冻结范围基本一致的情况下,换热管体缓慢降温可导致较大的岩土冻胀应力和出水管变形。

英文摘要：

The research background of this paper is the ground source heat pump（GSHP） technology applied in the field of agriculture energy conservation. The typical application is the GSHP used in greenhouse. However, the operating temperature of ground heat exchange pipe usually sustains below 0°C, when the GSHP runs during the winter night in cold regions. The sustaining low temperature can lead to pore water freeze and volume expansion in soil, which is called frost heave. In this paper, numerical simulation study was conducted to investigate the deformation of pipe-soil heat exchange structure due to frost heave. The numerical model, on the basis of porosity rate function, frozen soil constitutive equation, water content equation and phase change heat transfer theory, was built on the simulation platform ABAQUS and thermal-mechanical coupled subroutine compiled in Fortran. The semicircle soil computational domain and U-pipe were adopted in 2-D geometrical model. Based on the assumptions of this model, its application was restricted to： 1） The initial soil is homogeneous and saturated; 2） The difference of soils inside and outside borehole is neglected; 3） The internal and external pressure of the pipe is uniform; 4） The heat transfer takes place by conduction only; 5） The operational mode of pipe is cooling or constant temperature. This numerical model was verified by frost heave experiment, and the verification included mainly soil freezing temperature field and pipe deformation strain. The result of verification showed that the temperature of center point in the freezing area had a maximum absolute error of 0.6°C, the freezing radius had a maximum relative error of 9.1%, and the pipe strains had a maximum relative error of 16.4%. This numerical model could be applied for the study of pipe-soil structure frost heave and deformation. By means of this model, the characteristics of soil stress and pipe deformation during soil frost heave were analyzed. The results showed that elliptical deformation appe