Abstract: In this paper,a nonlinear differential equation of pipelines is established by considering the BRAZIER effect.Then,the analytical solution to the J-Lay pipeline configuration is obtained through the singular perturbation theory,and such key parameters as the bending moment and the axial force of the pipeline are solved by means of the iterative method.Meanwhile,the analytical solution of the pipeline is proved to be correct by means of the finite element method.Finally,the influences of the tension,the water depth and the ocean currents on the configuration and bending moment of the J-Lay pipeline are investigated.Theoretical results show that (1) in the laying process of the J-Lay pipeline,the peak of the bending moment is always present in the pipeline section near the touch down point; (2) when the tension is increased in a certain range,the more smooth the pipeline configuration is,the smaller the peak value of the bending moment will be,which is beneficial to the pipeline laying; (3) when the other parameters are constant and the water depth increases,the increase of the bending moment peak value of the pipeline is not monotonous; and (4) when the current force is in the opposite direction of the pipe laying,the ben- ding moment peak value of the pipeline increases,which is detrimental to the pipeline laying.

Key words: thin-wall pipeline, nonlinearity, singular perturbation, analytical solution, bending moments