东北多年冻土区埋地输油管道周围温度场特征非线性分析

Non-linear Analysis of Temperature Fields around the Buried Oil-pipeline in Permafrost Regions,Northeast China

为解决冻土区输油管道周围土壤的温度计算问题，根据考虑相变瞬态温度场的控制微分方程，应用Galerkin法推导出了二维温度场的有限．元计算公式．以东北多年冻土区中俄原油管道工程为背景，根据该工程区的冻土条件和气候条件，应用该方法对温热型输油管道土壤温度场进行了计算预报与对比分析．结果表明：对于输送油温为15℃、直径为0.914m以及管顶埋深为2．0m的管道，在没有铺设保温材料情况下，管顶之上的土壤在管道运行的第1年就达到热平衡状态，同时土壤融化速率在第1年达到最大，随后4a时间里迅速减小，第5年后融化速率变化趋于稳定；管道运行一段时间后，管道周围的融化圈随冷暖季节的变化呈交替式的扩展；在管道运行30a后，融深〉10m，即管底下的融化层厚〉7m，而在铺设5～8cm的聚氨酯保温材料后，融深控制在3．08～3.88m，即管底下融化层厚为0．2～1．0m．因此，合理使用保温方法能有效防止冻土区管道冻害的发生，同时达到保护冻土环境的目的．

Based on the governing differential equations of the transient problem of temperature fields with phase change, the two-dimensional finite element formula of temperature fields around a buried pipeline in permafrost regions are obtained by using Galerkin＇s method. The soil temperature fields around the heated pipeline with and without insulation are analyzed and compared for 30-year operation, on the background of the oil-pipeline construction in Northeast China. It is found that the soil above the pipe would be able to achieve thermal balance condition, and the thawing velocity of frozen soils reaches peak value at the first year,then it begins to decrease in the following 4 years, getting to stable condition after the fifth year, the thawing cylinders of the soil around pipelines would be expanding alternately between cold and warm seasons and the thawing depth below the pipe could exceed 10 meters after 30-year operation when the oil temperature is keeping at 15℃. However, the thawing depth would be able to maintain between 3.08 m and 3.88 m, when pipeline employed the insulation with thickness of 5～8cm. Therefore, the insulation would be able to prevent thawing settlement and environmental damage of permafrost effectively.