Numerical Analysis On The Coupled Mechanism Of Water,temperature And Stress Fields Of Frozen Soil Around The Mohe-daqing Crude Oil Pipeline In Cold Regions With Thermosyphons

The Mohe-Daqing pipeline is an important crude oil pipeline running through cold region.The freezing and thawing problems of frozen soil may result in serious threats to the safe operation of buried pipeline.Thermosyphons are usually ways to solve this problem in frozen soil.Therefore,it is significant to study numerical simulation of coupled water-heat-stress fields of frozen soil around Mohe-Daqing pipeline with thermosyphons.The water-heat-stress fields of frozen soil were first investigated in this paper.Comparative study was also carried out for soil temperature field with and without thermosyphons to investigate the cooling effect of thermosyphons.It is evident that thermosyphons have great influence on temperature drop of permafrost,and this influence is especially magnificent in winter.In contrast to soil temperature without thermosyphons,installing the thermosyphons could reduce the soil temperature right beneath the pipeline by approximately 2 to 3 ?.Numerical results have been validated by field data.Based on the above model,influence of thermosyphons' s parameters on temperature field was also studied in this paper,such as distance between thermosyphon and pipeline,depth of thermosyphon,and angle of thermosyphon.Results show that when distance between pipeline and thermosyphon is smaller,the depth of thermyphon is larger,angle reaches to 15°,cooling influence of thermosyphon on soil down the pipeline is more evident.When depth of thermosyphons is smaller,angle reaches to 45°,cooling influence of thermosyphon on soil in horizontal direction is more evident.