crude oil pipeline, permafrost, thaw-settlement coefficient, superplastic moisture content, k-means clustering, entropy-extensible cloud model, Oils, fats, and waxes, TP670-699, Gas industry, TP751-762

Global warming has intensified the degradation of permafrost, and the thaw settlement of frozen soil can seriously threaten the safe operation of pipelines. Hence, it is very important to accurately evaluate the thaw settlement risk level of pipeline foundation soil. Herein, the four important factors influencing the thaw settlement, i.e., moisture content, void ratio, ice content and superplastic moisture content, were selected and weighted objectively by the entropy method, and on this basis, the thaw-settlement grade of pipeline foundation soil in permafrost regions was evaluated with the extensible cloud model. Through the practical application of the evaluation model in Mohe–Daqing section of China–Russia Crude Oil Pipeline, the results show that, in current standards, there are no sufficient indicators for evaluating pipe foundation soil,the limit moisture content is too large, and the boundary of thaw-settlement grade in k-means evaluation is not very clear.Instead, the entropy-extensible cloud model could avoid the blurring of the thaw settlement indicators and the uncertainty among the influencing factors, so that the evaluation results are more consistent with the actual situation. Therefore, this study could provide a scientific basis and theoretical reference for the protection against thaw settlement during the design and operation management of pipeline in permafrost regions.