Non-linear Analysis for the Characteristics of Thawing Cylinders around the Buried Heat Oil Pipeline in Permafrost Regions

Based on the governing differential equations of the transient problem of temperature fields with phase change, the two-dimensional finite element formula of computing temperature fields around a buried pipeline in permafrost regions are achieved by using Galerkin's method. The soil temperature fields around the heated pipeline are analyzed and compared for the operation period of 30-year. It is found out that the soil above the pipe would be able to achieve thermal balance condition, and the thawing velocity of frozen soils reaches peak value during the first year, the thawing cylinders of the soil around pipeline 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℃, which would result in damages such as thawing settlements, pipeline deformation and environmental destroy of frozen soils. Hence, more attention should be taken to the operation safety of pipelines and environmental problems brought by the heated pipeline.