Analytical model of oil pipeline overground transitions, laid in mountain areas

Abstract

Abnormal climate changes cause adverse physical and geographical processes (erosion of soils, waterlogging, flooding, etc.) over the world. This situation stipulates study on effect of soil foundation malleability on pipeline transition strength because of its important diagnostic value. The article develops an engineering approach for stress–strain state estimation of oil pipeline overground transitions, laid in mountainous areas. A mathematical statement was made and analytical solutions of the boundary-value problem were described, which take into account overland transition contact with soil foundation. In order to carry out the force analysis, a tubular rod simulated the oil pipeline contacting with the soil foundation on the adjacent to the overground transition section according to the Fuss-Winkler hypothesis. The overground transition was schematised with a thin-walled shell at the final stage of the assessment of strength. The maximum axial stresses were determined for overground transition operation, considering transition’s two-dimensional thermoelastic state. The final assessment of the strength was carried out according to the energy criterion. The proposed method for the overground transition simulation makes possible considering the soil foundation property effects on the behavior of the oil pipeline transition and presents the results in the form of concise analytical expressions convenient for engineering practice. The conducted researches showed the effect of significant redistribution of loading in the oil pipeline overground transition caused by changes of soil foundation stiffness. Also, the boundary effect of perturbation of the stressed state in adjacent underground sections was found. It was determined the zone sizes the boundary effect has significant manifestations. The boundary state of the pipeline is most often achieved in its lower fibers at a short distance from the edge of the underground section. The obtained results of researches were tested on real constructions of overground transitions of oil pipeline laid in mountainous areas.