Keyword: «frost heaving»

The article considers the spatial altitude of the pipeline affected by interaction with frost heaving. The study shows the results of measuring planned-high-altitude positions (PHAP) of the underground pipeline obtained in different seasons to identify the peculiarities of pipeline deformation from frost heaving. According to the data obtained, the deformations are of a complex shape. The spatial position of the pipeline changes after freezing and thawing of the soil, i.e., twice a year. The level of deformations is beyond the limits of safe operation. An observation of the current state of research on the impact of frost heaving on underground pipelines revealed that the applied mathematical models consider a deformation as a single arch. Our PHAP measurements show a complex picture – specifically, bulges are replaced by concavities.

Main pipelines are subjected to various exogenous processes in the permafrost area. The behavior of underground pipelines in permafrost soils is one of the main factors that affect their reliability. Frost heaving is one of the most dangerous processes that recur annually and can lead to pipeline bends in the vertical plane, sagging of individual sections, displacement, or loss of longitudinal stability. The article shows that the long-term monitoring of the planned-high-altitude position of the main gas pipeline revealed a section of the shore slope on the Khatasskaya channel of the river Lena, where intense deformations occur twice a year. The survey procedure is presented, and the graphs of their positions are provided. The changes in the planned-high-altitude position of the pipeline reach one meter. Thus, our hy-pothesis is confirmed.

As a result of seasonal thawing and freezing of the surrounding soil, an underground pipeline, laid in the permafrost area, undergoes vertical displacement changes twice a year. Complex deformations occur in some sections, manifesting as multiple arches transitioning into one another without intervals. This article proposes a methodology for assessing the stresses that occur in the pipeline in such sec-tions. An equation describing the vertical position of the underground pipeline, depending on the weight of the soil above and the reactions of the soil below, has been obtained. There is no need to explicitly specify longitudinal forces in the equation, which greatly simplifies field work in data collection. The soil reactions are determined by using the gradient descent method in solving the equation.

Trunk pipelines laid on the territory of Yakutia are operated in the area of permafrost. A particular hazard in the floodplain area for underground pipelines is moisture migration during freezing and thawing of frozen soils, from which the pipeline changes position twice a year. The article provides an assessment of mechanical stresses from deformations created by frost beams. Mathematical description and selection of underground pipeline model, as well as determination of soil reaction are proposed, obtained position functions by point horizontal and vertical measurements and evaluation of stresses in underground pipeline are shown.

The main pipelines laid on the territory of Yakutia are subject to faster wear due to the influence of permafrost soils on their operational reliability. The article shows that long-term monitoring of the planned altitude position of the main gas pipeline has identified a section of the coastal slope on the Tabaginskaya bayou, in which intense deformations occur twice a year. A mechanism is proposed that leads to complex deformations of the underground pipeline during frost heaving at the moment of the beginning of freezing of the soil. The developed mathematical model confirms this mechanism in the first approximation.