CALCULATION OF UNDERGROUND PIPELINE STRENGTH WHEN WATER-SATURATED SOIL FREEZING

Currently in the oil and gas industry, the most common is the underground pipeline laying. Underground pipeline laying is also used in water-saturated soils. When water-saturated soil freezes, due to ice expansion, a force acts on the pipeline outer surface. This force leads to the appearance of compressive hoop stress in the pipeline wall and can lead to the pipe wall stability loss. For various reasons, there may be water in the cavity of an underground pipeline laid in water-saturated soil. Due to negative temperatures and water-saturated soil freezing, ice will be formed in the soil, as well as in pipeline cavity. In this case, the expansion force of ice in pipeline cavity creates internal pressure on the pipe, alongside with a ring tensile stress. The expansion force of ice in the soil creates external pressure on the pipe with the occurrence of hoop compressive stress. The need to ensure environmental safety of pipeline system operation in the oil and gas industry involves assessing the strength of an underground pipeline laid in water-saturated soil and containing water in the pipe cavity under the influence of ice expansion forces.The aim of research: ensuring environmental safety based on assessing the strength and stability of the pipeline wall due to ice expansion forces.Object of research: environmental safety, pipeline or its sections under the influence of ice expansion forces.Research methods: theoretical studies of the stress-strain state of pipelines in water-saturated soil containing water in the pipe cavity during the onset of sub-zero temperatures, when the pipes are exposed to external and internal ice expansion forces.Analytical expressions are obtained to determine the pressure on the surface of a pipeline laid in water-saturated soil and containing water in the cavity due to ice formation in the soil and in the pipe cavity.