Submarine Pipeline-soil Coupling

Submarine pipeline and soil interaction is the key problem of the pipeline design. The constitutive models of soil, such as nonlinear elastic, porous elastic and elastic-plastic model are adopted relatively, and the pipe/soil interaction is analyzed by using the common finite element software ABAQUS program. The aim to study the resistance displacement of submarine pipeline is to obtain each resistance displacement curve of constitutive model on each direction, and applied resistance displacement curve to calculate pipeline stress distribution and displacement distribution under submerged weight and environmental loads.Because the pipe and soil are two kinds of different materials, the effect of interface is considered by establishing the pipe-soil contact pair prescribed in the program.First, this paper compile the program of soil constitutive nonlinear elastic model in Fortran language, and embed in ABAQUS to submarine pipe lines with static calculation and analysis. By calculating result, a submarine pipeline in the soil resistance displacement curve has obtained in every direction. Each direction resistance displacement curve can get the nonlinear elastic rigidity coefficient of soil in the direction corresponding. In addition, based on single span submarine pipeline as an example, Using the above the rigidity coefficient of elastic springs simulation of nonlinear soil, and as the single span pipe boundary conditions. Calculated the displacement variations and stress distributions in single span pipeline in gravity and environment load.The previous experimental study indicates that the seepage of the soil plays an important role in the pipe/soil interaction. So the porous elastic model is used secondly. This paper compile a subroutine about void ratio of soil, Using ABAQUS obtains the resistance displacement curve of pipe in the soil in every direction. By resistance displacement relation curves, I obtained spring stiffness of the soil porous elastic models. Using the soil model simulation single span pipeline boundary conditions, calculate the single span pipe stress distribution and its displacement relationship in gravity and environment load.Soil deformation includes both elastic deformations also include plastic deformations. This article obtains the rigidity coefficient of soil in each direction from the soil of elastic-plastic model. Take the submarine single span pipeline as an example. By the spring simulated pipeline and soil contact boundary conditions, investigation of pipe stress distribution and displacement variation relationship. Finally, this paper compared and analyzed resistance displacement curves of three kinds of soil model. The results of calculation and the ALA regulating calculation results were compared. The results of the study indicate that three soil resistance displacement curve changing trends obviously different and porous model and regulation are most closely. The results offer the theory gist for the pipe/soil interaction design.