The article provides brief information on the design features of concreted pipes used in recent years in the construction of offshore pipelines, as well as in the overhaul of main pipelines operated in difficult engineering and geological conditions. The problem is setting of the stress-strain state of an underwater section of an offshore oil pipeline consisting of a blurred bare part and jointly deforming with it adjacent underground parts in which the soil was not subjected to flooding. The following statements of the problem of the stress-strain state of the calculated section of the oil pipeline are considered: 1) taking into account the effect of internal pressure and temperature stresses on the bending of the pipeline, causing additional bending of the gas pipeline; 2) neglecting the effect of internal pressure and temperature stresses on the bending of the concreted pipe. A method for joint numerical integration of differential equations describing the stress-strain state of a blurred exposed part and adjacent underground parts has been developed. Computer calculation programs have been compiled, in which constant integrations have been found, plots of the main characteristics of the stress-strain state along the entire length of the considered section of the oil pipeline have been constructed. Calculations of the main characteristics of the stress-strain state are carried out, diagrams of pipeline deflection and bending stresses are constructed. The tables show the extreme values of deflection and bending stresses from span and support bending moments for various values of operating parameters and soil conditions on adjacent underground parts. The influence on the ascent of the concreted pipe of the length of the blurred bare part, the parameters of operation, the weakening of the rigidity of soils due to their liquefaction in the underground part was revealed. Recommendations are given to identify possible causes of its ascent, as well as a description of the method of returning the pipeline to its design position.
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