Numerical Analysis of the Thermal Impact of Parallel Buried Pipelines on Permafrost Foundations

In permafrost regions, buried oil pipelines have a substantial thermal impact on the surrounding permafrost due to the large temperature difference between the oil and ground. The change in the thermal regime of the permafrost may trigger frost heave and thaw settlement of the pipeline, and can even destroy the pipeline. In this paper, an example of parallel-buried pipelines is performed, and a numerical method is employed to simulate the thermal impact of pipelines on permafrost foundations for both ice-poor and ice-rich permafrost with various kinds of distances between parallel pipelines. The results show that the thermal effect caused by the operation of pipelines can increase the temperature of permafrost, as well as cause the underlying permafrost foundation to thaw gradually. The thermal impact of parallel pipelines on the permafrost foundation depends on the distance between the parallel pipelines, ice content of the permafrost, initial permafrost temperature, and so on. The degree of influence on each other decreases as the distance between parallel pipelines increases. With an insulated pipeline that has been in operation for 50 years, the thaw depths under the parallel pipelines, with distances of 5 m, 10 m, and 15 m, increase by 1.4 m, 0.4 m, and 0.1 m compared to the single pipeline in the ice-rich permafrost district with the average ground temperature being −0.5°C and the ice content being 35%. Nevertheless, there is no difference between the single and parallel pipelines if the distance is more than 20 m. The recommended distance between parallel pipelines in this district should be greater than 15 m. Different permafrost districts should set separate recommended distances, and the corresponding protective measures should be made outside the recommended distance.