海床土体减缓坠物对海底管道撞击作用的研究
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摘要
海底管道受坠物撞击的损伤分析中,海床土体是不宜忽略的因素。基于耦合欧拉-拉格朗日算法(CEL法),该文建立了模拟坠物撞击海底管道过程中土体变形的有限元模型,并进行了物理模型试验,二者结果吻合较好。针对粘土海床,分析了海床柔性、海床土质、管道埋深、摩擦及坠物形状对海底管道损伤的影响。研究表明:对于裸置管道,海床柔性使一部分撞击能量转化为管道的整体变形,减轻管道局部损伤;对于埋置管道,基于软件的二次开发,考虑了正常固结粘土及均质粘土两种情况,二者的安全埋深相差较大。综合考虑上述土质的影响,2 m的埋深可提供有效的保护;埋深超过1 m时,坠物与土体间的摩擦系数对管道损伤的影响更加明显;形状尖锐的坠物受到土体的阻力较小,对管道造成的损伤程度较大。不同形状的坠物撞击管道时,管道的变形特征存在差异。研究结果对管道的风险评估及安全埋深设计具有指导意义。
Seabed plays an important role in the analysis of submarine pipeline subjectd to impact loads. Based on the coupled Eulerian-Lagrangian method(CEL method), a finite element numerical model is established to simulate the soil deformation involved in the impact process. Meanwhile, physical model tests are carried out. The numerical simulation results show good agreement with test results. Aiming at seabed in clay, a series of influence factors on pipeline damage have been analyzed, including the seabed flexibility, soil property, embedment depth,friction, and dropped object shape. For pipelines resting on seabed surface, part of the impact energy will be dissipated through pipeline global deformation due to bed flexibility, which can relieve the pipeline local damage.For buried pipelines, either the normally consolidated clay or the homogeneous clay is considered. The safe embedment depth of these two conditions differs significantly. Considering the aboved soil conditons, an embedment depth of approximately two meters can provide effective protection for pipelines. The friction coefficient between the dropped object and soil has influence on the dissipation of impact energy and pipeline damage, which is signficant when the embedment depth exceeds one meter. Dropped object in sharp shape can casue servere damage because of less resitance from soil. Besides, there are some differences between deformation characteristics of pipelines, which are influenced by dropped objects in various shapes. The research results are expected to provide reference for risk assessment and safe embedment depth design of submarine pipelines.
Seabed plays an important role in the analysis of submarine pipeline subjectd to impact loads. Based on the coupled Eulerian-Lagrangian method(CEL method), a finite element numerical model is established to simulate the soil deformation involved in the impact process. Meanwhile, physical model tests are carried out. The numerical simulation results show good agreement with test results. Aiming at seabed in clay, a series of influence factors on pipeline damage have been analyzed, including the seabed flexibility, soil property, embedment depth,friction, and dropped object shape. For pipelines resting on seabed surface, part of the impact energy will be dissipated through pipeline global deformation due to bed flexibility, which can relieve the pipeline local damage.For buried pipelines, either the normally consolidated clay or the homogeneous clay is considered. The safe embedment depth of these two conditions differs significantly. Considering the aboved soil conditons, an embedment depth of approximately two meters can provide effective protection for pipelines. The friction coefficient between the dropped object and soil has influence on the dissipation of impact energy and pipeline damage, which is signficant when the embedment depth exceeds one meter. Dropped object in sharp shape can casue servere damage because of less resitance from soil. Besides, there are some differences between deformation characteristics of pipelines, which are influenced by dropped objects in various shapes. The research results are expected to provide reference for risk assessment and safe embedment depth design of submarine pipelines.
引文
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[15]Lou M,Ming H Q.Dynamic response analysis of the submarine suspended pipeline impacted by dropped objects based on LS-DYNA[J].Marine science bulletin,2015,17(2):39―55.
[16]Gao P,Duan M L,Gao Q,et al.A prediction method for anchor penetration depth in clays[J].Ships and offshore structures,2016,11(7):782―789.
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[20]李书兆,李亚,鲁晓兵.桩基贯入过程中土体大变形分析与流动机理研究[J].工程力学,2017,34(6):157―165.Li Shuzhao,Li Ya,Lu Xiaobing.Large deformation analysis and flow mechanism study of the soil during pile penetration[J].Engineering Mechanics,2017,34(6):157―165.(in Chinese)
[21]Cosham A,Hopkins P.The effect of dents in pipelines-guidance in the pipeline defect assessment manual[J].International Journal of Pressure Vessels and Piping,2004,81(2):127―139.
[22]王自力,蒋志勇,顾永宁.船舶碰撞数值仿真的附加质量模型[J].爆炸与冲击,2002,22(4):321―326.Wang Zili,Jiang Zhiyong,Gu Yongning.The added mass model of ships collision simulation[J].Explosion and shock waves,2002,22(4):321―326.(in Chinese)
[23]Noh W F.CEL:A time-dependent,two-spacedimensional,coupled eulerian-lagrangian code[C].Methods in Computational Physics.New York:Academic Press,1964,3:117―179.
[24]Jiang H,Xie Y.A note on the Mohr-Coulomb and Drucker-Prager strength criteria[J].Mechanics Research Communications,2011,38(4):309―314.
[25]殷齐麟,董胜,樊敦秋.复杂地层中自升式平台插桩的数值模拟[J].工程力学,2016,33(9):204―211.Yin Qilin,Dong Sheng,Fan Dunqiu.Nuerical simulation of penetration of jack-up platform in complex foundation soils[J].Enginnering Meachinics,2016,33(9):204―211.(in Chinese)
[26]Zeinoddin M,Arabzadeh H,Ezzati M,et al.Response of submarine pipelines to impacts from dropped objects:Bed flexibility effects[J].Internationl Journal of Impact Engineering,2013,62(4):129―141.
[27]GBT 546―2016,霍尔锚[S].北京:中国标准出版社,2016.GBT 546―2016,Hall anchor[S].Beijing:Standards Press of China,2016.(in Chinese)
[2]Longva V,S?vik S,Levold,et al.Dynamic simulation of subsea pipeline and trawl board pull-over interaction[J].Marine Sturcutres,2013,34(4):156―184.
[3]Gao Q,Duan M,Liu X,et al.Damage assessment for submarine photoelectric composite cable under anchor impact[J].Applied Ocean Research,2018,73:42―58.
[4]Ghosh S K,Jhonson W,Reid S R,et al.On thin rings and short tubes subjected to centrally opposed concentrated loads[J].International Journal of Mechanical Sciences,1981,23(4):183―194.
[5]Jones N,Birch S E,Birch R B,et al.An experimental study on the lateral impact of fully clamped mild steel pipes[J].Proceedings of the institution of Mechanical Engineers,Part E:Journal of Process Mechanical Engineering,1992,206(2):111―127.
[6]Ellinas C P,Walker A C.Damage on offshore tubular bracing members[C]//IABSE Colloquium on Ship Collisions With Bridges and Offshore Structures.Copenhagen,1983:253―261.
[7]Bai Y,Pedesren P T.Elastic-plastic behaviour of offshore steel structures under impact loads[J].International Journal of Impact Engineering,1993,13(1):99―115.
[8]Jones N,Shen W Q.A Theoretical study of the lateral impact of fully clamped pipelines[J].Proceedings of the institution of Mechanical Engineers,Part E:Journal of Process Mechanical Engineering,1992,206(2):129―146.
[9]Wierzbicki T,Suh M S.Indentation of tubes under combine loading[J].International Journal of Mechanical Sciences,1988,30(3/4):229―248.
[10]粟京.DNV96版《海底管道系统规范》对冲击防护的新规定[J].石油工业技术监督,1999,15(2):15―17.SU Jing.New states of the shock protection in DNV96version of marine pipe system standard[J].Technology Supervision in Petroleum Industry,1999,15(2):15―17.(in Chinese)
[11]任艳荣,刘玉标,顾小芸.弹塑性海床上的管土相互作用分析[J].工程力学,2004,21(2):84―88.Ren Yanrong,Liu Yubiao,Gu Xiaoyun.Analysis of pipe/soil interaction on elastic-plastic seabed[J].Engineering Mechanics,2004,21(2):84―88.(in Chinese)
[12]Robert D J.A modified Mohr-Coulomb model to simulate the behavior of pipelines in unsaturated soil[J].Computers and Geotechnics,2017,91:146―160.
[13]Yu J X,Zhao Y Y,Li T Y,et al.A three-dimensional numerical method to study pipeline deformations due to transverse impacts from dropped anchors[J].Thin-Walled Structures,2016,103:22―32.
[14]杨秀娟,闫涛,修宗祥,等.海底管道受坠物撞击时的弹塑性有限元分析[J].工程力学,2011,28(6):189―194.Yang Xiujuan,Yan Tao,Xiu Zongxiang,et al.Elastic-plastic finite element analysis of submarine pipeline impacted by dropped objects[J].Engineering Mechanics,2011,28(6):189―194.(in Chinese)
[15]Lou M,Ming H Q.Dynamic response analysis of the submarine suspended pipeline impacted by dropped objects based on LS-DYNA[J].Marine science bulletin,2015,17(2):39―55.
[16]Gao P,Duan M L,Gao Q,et al.A prediction method for anchor penetration depth in clays[J].Ships and offshore structures,2016,11(7):782―789.
[17]王懿,贾旭,黄俊,等.基于CEL的船舶抛锚入泥度分析[J].石油机械,2014,42(12):44―47.Wang Yi,Jia Xu,Huang Jun,et al.Analysis of penetration depth of dropped anchor based on CEL[J].China Petroleum Machinery,2014,42(12):44―47.(in Chinese)
[18]DNV-RP-F107 Risk assessment of pipelines protection[S].Oslo:Det Norske Veritas,2010.
[19]庄元,宋少桥.海底管线埋深问题研究[J].大连海事大学学报,2013,39(1):61―64.Zhuang Yuan,Song Shaoqiao.Study on the depth of submerged pipeline[J].Jounral of Dalian Maritime University,2013,39(1):61―64.(in Chinese)
[20]李书兆,李亚,鲁晓兵.桩基贯入过程中土体大变形分析与流动机理研究[J].工程力学,2017,34(6):157―165.Li Shuzhao,Li Ya,Lu Xiaobing.Large deformation analysis and flow mechanism study of the soil during pile penetration[J].Engineering Mechanics,2017,34(6):157―165.(in Chinese)
[21]Cosham A,Hopkins P.The effect of dents in pipelines-guidance in the pipeline defect assessment manual[J].International Journal of Pressure Vessels and Piping,2004,81(2):127―139.
[22]王自力,蒋志勇,顾永宁.船舶碰撞数值仿真的附加质量模型[J].爆炸与冲击,2002,22(4):321―326.Wang Zili,Jiang Zhiyong,Gu Yongning.The added mass model of ships collision simulation[J].Explosion and shock waves,2002,22(4):321―326.(in Chinese)
[23]Noh W F.CEL:A time-dependent,two-spacedimensional,coupled eulerian-lagrangian code[C].Methods in Computational Physics.New York:Academic Press,1964,3:117―179.
[24]Jiang H,Xie Y.A note on the Mohr-Coulomb and Drucker-Prager strength criteria[J].Mechanics Research Communications,2011,38(4):309―314.
[25]殷齐麟,董胜,樊敦秋.复杂地层中自升式平台插桩的数值模拟[J].工程力学,2016,33(9):204―211.Yin Qilin,Dong Sheng,Fan Dunqiu.Nuerical simulation of penetration of jack-up platform in complex foundation soils[J].Enginnering Meachinics,2016,33(9):204―211.(in Chinese)
[26]Zeinoddin M,Arabzadeh H,Ezzati M,et al.Response of submarine pipelines to impacts from dropped objects:Bed flexibility effects[J].Internationl Journal of Impact Engineering,2013,62(4):129―141.
[27]GBT 546―2016,霍尔锚[S].北京:中国标准出版社,2016.GBT 546―2016,Hall anchor[S].Beijing:Standards Press of China,2016.(in Chinese)
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