Hydrodynamic Test Research Of Spanning Pipes Under The Combined Effect Of The Earthquake Wave Flow

With the rapid development of offshore oil industry, submarine pipelines, an important mode of transportation of oil and gas. has been widely used and are referred to be the lifeblood of offshore oil and gas fields. However, complicated Marine factors seriously affect the safety of subsea pipelines. Once the safety accidents of submarine pipelines occur, our country will deal with significant economic losses and serious social influence. Therefore, it is of important theoretical significance and practical value to research of submarine pipeline damage mechanism, structure analysis carried out on the submarine pipeline and the effective technical means for health monitoring of submarine pipelines. The South China Sea located between tropical and subtropical, waters vastly, seabed topography complicated, bearing kinds of natural disasters.such as waves and internal waves, from the influence of the trend, north to warm, south cold. etc. So the wave flow load has become an important factor which affects the safety of submarine pipelines. Submarine pipelines come into being the inevitable dangling under the wave flow scour and the scour, the change of the seabed, residual stress and thermal stress.In this paper, the research, discussing nonlinear analysis of free spanning submarine pipelines subjected to the wave and water flown, includes:(1) We calculate the dynamic modulus of elasticity based on the cantilever pipe fundamental frequency. It is difficult to achieve complete cantilever pipe embedded in the concrete pier via comparison of test results and theoretical results which are similar to each other. This experiment research provides an important reference value for the experiment model of cantilever end.(2) Two kinds of circumstances are considered in the test, pipe with water and no water. In both cases, contrast central pipe stresses and to strain, we can know that, the dynamic response of the pipe with water should be larger than that of the one without water.(3)In the test, we take into account different span length of offshore pipeline affected by wave load. Compared test results of submarine pipeline under seismic load with the experimental results under wave load, experimental data show that the pipe strain increased along with the increase of span length. Reaction increases more obviously, the longer span. The span length of pipeline is the main factor of the dynamic response of seabed pipeline which is different from that under the earthquake action.(4) In the test, the results showed that the strain of the pipeline decreases with the increasing height of wave and the decreasing trend is not obvious. Experimental data showed that wave height is not the main factors that affecting dynamic response of suspended span pipeline.(5) Measuring the influence of wave height on different location of central pipe in the tests, we can sec from the experimental data analysis that the point7of the central pipe responses strongly. The results of the experiment illustrated that the interaction between water flow and pipeline under wave action is relatively complicated. Pipeline model for numerical analysis should be established with many factors considered.(6)The height of suspended span is also the important factors affecting pipeline dynamic response. We research the dynamic response of the pipeline with different water depth by simulating different span the height. Test result shows that with the increase of water depth, dynamic response of pipe decreases. Experiments show that with the span height increasing gradually, the dynamic response of pipeline increases. The experiment shows the suspended span height is an important factor of affecting dynamic response of the suspended span submarine pipeline.(7)Comparin.g dynamic response of the submarine pipeline under the wave How action to that ofthe submarine pipeline under the action of earthquake, we discuss different dynamic response mode of submarine pipeline.(8) According to the analog output data of ADINA System and experimental data, we can learn that the results on across nodes of the simulation of spanning submarine pipeline-wave the three-dimensional solid model are greater than the experimental results of physics model, but the results on cross-end nodes ofthe simulation are close to that of physics model.