Dynamic Response Characteristics Of Spanning Pipes Under The Combined Effect Of The Earthquake Wave Current

Submarine pipeline is the most economical and efficient way to transport oil and gas resources.Due to the complexity of wave flow erosion and seabed topography,it is easy to appear the span part of the pipeline?When the wave current and earthquake load acting on the pipeline,the support of both sides of seabed soil is affected by the acceleration and displacement caused by the earthquake.The cross section of the suspension is subjected to the action of hydrodynamic pressure caused by the wave current,mutual coupling of loads has a serious threat to the safe operation of submarine pipelines.Therefore,it has great social significance and engineering value to study the dynamic response characteristics of submarine pipeline under complex loads.In this paper,the physical model experiment and the finite element numerical simulation method are used to study the dynamic response of submarine pipeline under the action of multiple loads of wave?current and seismic,and provide suggestions for practical engineering.The model test was carried out in the laboratory of underwater earthquake simulation system at Dalian University of Technology.Based on the measured acceleration and dynamic water pressure data,the influence of the length of suspension,the state of the pipe and the external load on the fundamental frequency and dynamic response of the pipeline is analyzed.Experimental results show that with the increase of the span length,the natural vibration frequency of the pipeline decreases and the dynamic response increases significantly;The increase of flow velocity,wave height and period in a certain range will increase the dynamic response;The dynamic response of three kinds of loads acting on the pipeline is greater than load acting separately;The earthquake load plays a leading role,and the wave and current load play a minor role.Numerical simulation is carried out by using ADINA finite element software.First of all,setting up the experiment pipeline model,simulation and test in the same condition,get the result of dynamic response of pipeline,and compared with the experiment data,the results show that the software can simulate realistic dynamic response characteristic of free spanning pipelines.After the demonstration of software's reliability,considering the pipe soil contact and cross shoulder span pipe prototype pipeline water coupling model further,based on the determination of the contact length of pipe soil,the influence of the factors such as the elastic-plastic characteristics of the seabed soil and the buried depth of the pipeline on the dynamic response of the pipeline is discussed.Based on the analysis of the data of axial stress and circumferential stress in the key parts of pipeline,the following conclusions are obtained: Under the change of the thickness and radius of the pipe wall,the dynamic response of the key parts is not the same between the different load combinations;With the increase of the elastic modulus and cohesion of the seabed soil,the dynamic response of the pipeline decreases gradually;With the increase of buried depth,the dynamic response increases first and then decreases;The influence of soil properties on the dynamic response of the contact part is greater than that of the middle section.