Heat and Moisture Transfer in the Soil Base of Pipelines with Aufeis

Long-distance trunk pipelines in permafrost areas are subject to various exogenous processes. The pipeline, especially in mountainous areas, crosses the water barrier, which in winter is covered with ice. The interaction of pipelines with ice is not well researched. The purpose of this work is the numerical simulation of the heat and moisture conditions of the soil base of the gas pipeline during the formation of ice. We present a mathematical model of heat and moisture transfer taking into account the actual process of freezing and thawing of the pore solution of soil in the temperature spectrum. The numerical experiment was performed using the recovered heat flow of the icy valley by the method of solving boundary inverse problems of heat conduction. As a result of a numerical experiment, we established that the formation of ice occurs in the second half of winter and has a warming effect. In the first half of the summer period, there is intense thawing of ice and the dynamics of the depth of seasonal thawing comes with some delay, but at the beginning of the winter period, it is restored similarly to regular soil. Suprapermafrost groundwater increases the average annual temperature of the soil around the pipeline and has a warming effect. In this case, the gas pipeline, which is located across the flow, blocking the movement of groundwater, changes the process of the formation of a frozen mass in the soil. Thus, in the summer period, the process of thawing on an icy glade comes with some delay, and at the end of the summer period, the thawing depth coincides with regular soil. The permafrost water acts as a warming agent, thereby raising the average annual temperature of the soil around the pipeline.

frozen soils, aufeis, gas pipeline, heat and moisture transfer, suprapermafrost groundwater, heat flow recovery

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