余杨, 李振眠, 余建星, 孙文正, 刘晓伟, 马建东, 刘成. 穿越平移断层海底埋地管道屈曲失效分析[J]. 工程力学, 2022, 39(9): 242-256. DOI: 10.6052/j.issn.1000-4750.2021.05.0391
引用本文: 余杨, 李振眠, 余建星, 孙文正, 刘晓伟, 马建东, 刘成. 穿越平移断层海底埋地管道屈曲失效分析[J]. 工程力学, 2022, 39(9): 242-256. DOI: 10.6052/j.issn.1000-4750.2021.05.0391
YU Yang, LI Zhen-mian, YU Jian-xing, SUN Wen-zheng, LIU Xiao-wei, MA Jian-dong, LIU Cheng. BUCKLING FAILURE ANALYSIS OF SUBSEA BURIED PIPELINE CROSSING STRIKE-SLIP FAULT[J]. Engineering Mechanics, 2022, 39(9): 242-256. DOI: 10.6052/j.issn.1000-4750.2021.05.0391
Citation: YU Yang, LI Zhen-mian, YU Jian-xing, SUN Wen-zheng, LIU Xiao-wei, MA Jian-dong, LIU Cheng. BUCKLING FAILURE ANALYSIS OF SUBSEA BURIED PIPELINE CROSSING STRIKE-SLIP FAULT[J]. Engineering Mechanics, 2022, 39(9): 242-256. DOI: 10.6052/j.issn.1000-4750.2021.05.0391

穿越平移断层海底埋地管道屈曲失效分析

BUCKLING FAILURE ANALYSIS OF SUBSEA BURIED PIPELINE CROSSING STRIKE-SLIP FAULT

  • 摘要: 长输海底管道常不可避免地穿过地震断层,地震断层活动可能导致管道发生扭曲、皱折甚至断裂,极大威胁管道安全。采用创新性的向量式有限元方法(VFIFE)分析穿越地震断层海底管道屈曲失效行为,首先推导考虑材料非线性的VFIFE空间壳单元计算公式,提出适用壳单元的非线性管土耦合模型,然后重点解决了海底管道屈曲及屈曲传播过程中存在的内壁自碰撞接触问题,编制了Fortran计算程序和相应后处理程序。通过文献对比证明了模型的正确性。开展了平移断层作用下空载状态海底管道屈曲失效过程模拟,分析了穿越角度、土体性质和水压大小对海底管道屈曲失效行为的影响,结果表明:海底管道径厚比小,用钢等级高,周围土体强度低,具有更高的抵抗断层位移载荷能力;较低外压和平移断层联合作用下,管道变形呈S形,屈曲失效由断层位移引起的过度弯曲主导,失效模式是第二个弯曲处或者两个弯曲处的受压侧出现明显内陷,截面变形呈椭圆形;穿越角度越小,屈曲失效的临界断层位移越小;周围土体强度越高(砂土>黏土>淤泥夹砂),管道弯曲变形越严重,屈曲失效的临界断层位移越小;较高外压和平移断层联合作用下,屈曲失效由外压主导,主要模式是第一个弯曲处或者第二个弯曲处首先出现压溃,然后发生屈曲传播现象;不同水压和平移断层位移组合下海底管道破坏程度不一,压溃位置、屈曲传播方向和范围、截面变形呈现不同模式。结果可用于指导穿越地震断层海底管道抗震设计和止屈防护研究。

     

    Abstract: Long-distance subsea pipelines often inevitably pass through seismic faults which may impose great threats to pipeline safety, such as twist deformation, wrinkling and tensile rupture. The innovative vector finite element method (VFIFE) was used to analyze the buckling failure behavior of subsea buried pipeline crossing seismic faults. First, the calculation formula of the VFIFE 3D thin shell element were derived considering the material nonlinearity and a custom-made nonlinear pipe-soil interaction model was proposed for the shell element. Then we focused on solving the self-collision contact problem of the inner wall of the pipeline during its collapse and buckle propagation. A Fortran program as well as a corresponding post-processing program was developed. The computation models were verified through a comparison with the published results. A simulation of the buckling failure process of empty subsea pipeline under the strike-slip faults was carried out, and the influences of crossing angle, soil property and water pressure on the buckling failure behavior were analyzed. The results show that the subsea pipeline can hold a higher capacity against fault displacements due to its small diameter-thickness ratio, high steel grade and softer surrounding soil. Under the combined action of lower external pressure and strike-slip faults, the deformation of the subsea pipeline is S-shaped and the buckling failure is dominated by excessive bending caused by fault displacements. The buckling mode is that the compression side of the second bend or both the two bends undergo obvious invagination and the cross-section deformation is elliptical. Under such loads, the smaller the crossing angle, the smaller the critical fault displacement for buckling failure of the pipeline; the higher the strength of the surrounding soil (sand>clay>slit and sand), the more serious the bending deformation and the smaller the critical fault displacement for buckling failure. Under the combined action of high external pressure and strike-slip faults, the buckling failure is dominated by external pressure. The main mode is that the first or second bend collapses firstly and then buckle propagation occurs. Under different combinations of water pressure and fault displacement, the degrees of destruction of the pipeline are different. Moreover, the collapse position, the direction and range of buckle propagation, and deformed cross-sectional shape exhibit different patterns. The results can be used to guide the seismic design and buckling prevention research of subsea pipeline crossing seismic faults.

     

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