穿越走滑断层海底管道局部屈曲研究及应变响应预测

Research on local buckling and strain response prediction of submarine pipelines across strike-slip faults

海洋地震频繁且海底土体环境复杂,当地震导致断层土体发生永久变形后,穿越断层的海底埋地管道也将受迫发生变形。为确定变形后的管道能否正常工作,需根据实际工况对其进行应变响应预测。首先通过有限元计算软件ABAQUS建立管道与走滑断层的三维实体模型,模拟管-土间的接触作用并通过等效边界方法修正模型,得到管道局部屈曲破坏形式及应变分布情况。然后,通过调整有限元模型参数对断层交角、管道工作内压、管道径厚比对管道极限塑性应变的影响进行敏感性分析,定性分析不同敏感性因素对穿越走滑断层海底管道应变响应的影响。最后,在数值模拟数据的基础上通过MATLAB软件利用基于遗传算法优化的BP神经网络实现对管道应变响应的精确预测。结果表明:穿越走滑断层管道在发生局部屈曲时,可根据轴向压缩应变突变现象确定管道局部屈曲时对应的断层位移,并且断层交角、管道工作内压和管道径厚比都会对跨断层管道应变响应产生影响。

Ocean earthquakes occur frequently and the environment of subsea soil is complex.When earthquakes cause permanent deformation of faults,the submarine buried pipelines acrossthe faults will also be forced to deform.It is necessary to predict the strain response of the pipeline according to the actual working conditions,in order to determine whether the the deformed pipe works well.In this paper,athree-dimensional solid model of the pipeline and strike-slip fault is established by the finite element software ABAQUS,and the contact action between the pipe and soil is simulated.The model is modified by an equivalent boundary method,and the local buckling failure form and strain distribution of the pipeline are obtained.The sensitivity analysis is carried out to study the influence ofthe crossing angle,pipeline internal pressure,pipeline diameter-thickness ratio and soil propertieson the ultimate plastic strain of the pipeline,by adjusting the parameters of the finite element model.The influence of different sensitivity factors on the strain response of the submarine pipeline crossing the strike-slip fault is qualitatively analyzed.Finally,based on numerical simulation data,the accurate prediction of the pipeline strain response is realized by using the optimized BP neural networks based on genetic algorithm with MATLAB software.The results show that when the local buckling occurs,the corresponding fault displacement can be determined according to the abrupt change of the axial compression strain,and the fault intersection angle,the internal pressure of the pipeline and the diameter-thickness ratio of the pipeline will affect the strain response of the pipeline across the fault.