海洋立管触地段横向地震动响应的试验研究

Experimental study on the dynamic response of a marine riser in touchdown zone under lateral earthquake

建立一套立管与海床相互作用的模型试验系统。开展了管-土作用模型在振动台上的模态试验和地震动试验,得到了管-土作用模型的横向固有频率和相应振型、沿立管触地段以及与其相邻的水平段和悬垂段轴向和环向的一些特征点在地震作用下的地震动响应。试验结果表明:横向地震作用下,立管水平段的应变响应非常小;立管触地段海底管道的应变响应很大,是立管结构最易产生损伤的关键部位;立管悬垂段也表现出较大的应变响应,是立管产生损伤的另一个关键部位;在横向地震作用下立管触地段侧边较正上方和正下方更易产生损伤;模型试验的成果丰富了海洋立管动力模型试验的研究内容,为优化海洋立管抗震设计、评估在役油气管道的抗震安全提供了科学依据。

A set of experimental system for testing the riser and seabed interaction was developed by using PVC pipeline and soft clay.Modal tests and seismic tests of the pipe-soil system on a large-sized shaking table were performed.The first three orders of transversal eigen frequencies and correspondent vibration mode shapes were obtained by the modal tests.The seismic responses at some feature points along the pipeline and pipe ring in touchdown zone as well as in adjacent surface zone and catenary zone were also observed.The results show the strain response of the riser in surface zone is very small under lateral seismic excitation.The maximum strain response appears in touchdown zone of the riser.The strain response of the riser in catenary zone is also severe,being another key part of the riser.In addition,the dynamic response in the lateral side of the pipeline is more severe than at the top and bottom of the riser under lateral seismic excitation.The test results enrich the knowledge of dynamic characteristics of the marine riser in touchdown zone,providing a scientific basis to the seismic design and safety assessment of risers in service.