Study On Mechanics Properties Of The "S" Type Sea Pipelines Under Laying Operation

During the pipe-laying operation with a lay-barge, one end of the pipeline is put on the seafloor, the other on the lay-barge, and the suspended part of the pipeline is very long, In case of the suspended pipeline overstressing, the mechanics properties of the pipeline should be analyzed quickly and accurately according to the marine environment, so that the reasonable working parameters of the lay-barge could be determined. In fact, the suspended pipeline has the nonlinear properties in geometry, its length and the force of the touch down point are unknown during laying operations, so that the question is difficult to be solved. Many methods of the pipeline analysis have been put forward during the past thirty years, but almost all of them are limited in the analysis accuracy, speed and universality. Little study on the beach pipeline-laying and related techniques has been done till now, and there isn't any analysis software of pipeline suitable for engineering in our country.To meet the requirements of the "S" type pipelines laying in our country, it is urgent to solve the problems of mechanics properties of the pipelines. This paper aims at the problem of "Research of the pipe laying technique and cable laying equipment on beach and shallow sea". The mechanics properties of the "S" type pipeline and related techniques are studied deeply in this paper.An analytical method is presented for finding the elastic deflection of the "S" type pipelines laid with an articulated stinger in which the buoyancy is adjustable. The stinger segment and the suspended segment of the pipeline are treated separately with a singular perturbation technique and by the use of some additional relation and the continuity condition at the joint between the two segments, an approximate solution of the second order to the deflection of the whole pipeline is obtained. The method not only considered the aspect of non-linearity, elasticity and large deformation of the pipeline but also fitted numerical calculation with computer. The proposed method can be not only used to treat with complex loads and boundaries but also applied to similar structures with little modification. In addition, the computer time required for the method is much less than that for the finite element method, so that optimization of the laying parameters can be performed. The results of the relationship among calculating speed, accuracy and universality are very well using this method.Based on the analysis and calculation on the pipelines, a MATLAB subroutine implementing the fundamental procedures of the proposed numerical theory is included. The 2-D model of the "S" type pipelines are analyzed and then researched the stress and the distortion of the pipelines under abandonment and recovery (A/R) operation using the non-linear finite element method.