Analytical Model for Non-Bonded Flexible Pipe Under High Temperature and Axisymmetric Load and its Application in Upheaval Buckling

Abstract In order to prevent pipe blockage and reduce transportation costs, submarine pipes usually use the method of heating and pressurizing the pipe when transporting liquids. The high temperature and high pressure will cause the axial deformation of the submarine pipe, but due to the existence of the boundary between the two ends of the pipe, the axial deformation cannot be released and a certain axial force is generated. When axial force accumulates to a certain extent, buckling failure may occur, that is, thermal buckling of submarine pipes. In the process of buckling prediction, the axial force is an important input parameter. In the current engineering application, the non-bonded flexible pipe is often regarded as a steel pipe for fast calculation of the axial force value. However, since the geometry of the non-bonded pipe is very complex, the radial mutual extrusion and interlayer interaction will affect the axial deformation of the pipe. Therefore, it is not appropriate to simply use the deformation of the steel pipe to obtain the equivalent of the deformation of the non-bonded pipe to obtain the value of the axial force. In this paper, an analytical model for calculating the structural response of non-bonded pipes under high temperature loads and axisymmetric loads is proposed, and the structural responses of non-bonded pipes under high temperature loads and internal and external pressures are analyzed. The axial force is compared with the results obtained by the calculation methods commonly used in the current engineering. Further, the impact of these differences on the soft soil seabed upheaval buckling forecast is analyzed.