基于中俄原油管道永冻区工程建设特点,建立冻土多孔介质水热耦合数学模型.地表环境温度采用周期性边界条件,利用SIMPLER算法进行数值求解,得到埋地热油管道自第一年4月末投产,不同月份土壤温度场、水分场、冰水相变界面移动规律随环境温度周期波动的变化关系,并利用ANSYS软件对土壤水热耦合温度场进行冻胀应力分析.结果表明:在地表温度的周期波动下,较长时间内管道周围土壤温度变化剧烈,且受温差和重力的影响,土壤中水分产生了沿管道中心线自上而下的自然对流,随地表以下不同土层温度的不断变化,自然对流涡旋中心形态及强度变化明显,温度梯度对水分迁移影响较大;随着地表温度的升高,管道上方土体的融沉速率略大于管道融沉速率;伴随着融化圈的不断扩大,管道附近土体受较小应力作用范围大,容易发生不均匀冻胀.%Based on the construction characteristics of Sino-Russian crude oil pipeline permafrost regions project, a mathematical model of porous medium coupling of moisture-heat of the frozen soil was established.The periodic boundary conditions were adopted for obtaining the ambient temperature and SIMPLER method was used for numerical simulation.The relationship between the cyclic swing of the ambient temperature and the rule of soil temperature, moisture field and ice phase change interface movement was obtained since the late April of the first year when the pipeline was put into operation.The frost heave stress with the field of temperature coupled with moisture was analyzed by the software ANSYS.The results show that the soil temperature around the pipeline changes dramatically in a long period due to the periodic fluctuations of earth' s surface temperature.Top-down free convection of the moisture contained in the soil is generated along the center line of the pipeline by the effect of temperature difference and gravity.The modality and intensity in the vortex center of the free convection change significantly with the underground soil temperature changing, and water translocation can be easily impacted by the temperature gradient.At the same time, as the rise of the surface temperature, the thawing rate of soil above pipe is slightly larger than that of the pipe.As the melting cycle expands, the soil around pipe impacted by the small stress range is prone to form heterogeneous frost heaving.
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