青藏高原北部移动冰丘破坏桥墩的数值模拟  

Numerical Modelling on Migrating Pingo Destructing Bridge Pier in North Tibetan Plateau

作　　者：吴珍汉[1] 王连捷[1] 胡道功[1] 吴中海[1] 叶培盛[1] 

机构地区：[1]中国地质科学院地质力学研究所,北京100081

出　　处：《现代地质》2006年第2期239-251,共13页Geoscience

基　　金：科技部国际科技合作重点项目(2001CB711001);中国地质调查局国土资源大调查项目(1212010541403)

摘　　要：青藏高原北部常年冻土区断裂破碎带发育的移动冰丘对桥梁、涵洞、输油管道等工程设施具有不同形式的破坏作用。考虑移动冰丘与工程设施的相互作用,根据野外观测和实验资料设计模型,应用三维有限元数值模拟方法,计算移动冰丘冻胀产生的位移场、应力场和桥墩弯曲应力,分析桥墩破裂机理。结果表明,移动冰丘能够产生11^-21MPa的轴向应力和15^-31 MPa的主应力,在桥墩周围形成不同规模的应力集中区,导致桥墩发生显著偏移。桥墩的偏移和弯曲能够在桥墩内部产生高达61.9~64.6 MPa的张应力和-45.0^-49.0 MPa的压应力,超过桥墩的强度极限。在粗细桥墩连接部位,外侧形成张应力集中区,最大张应力达26~30 MPa;内侧形成压应力集中区,最大压应力达-25^-28.8 MPa。粗细桥墩连接部位外侧的张应力超过了钢筋混凝土的抗张强度,产生与野外观测资料基本吻合的桥墩破裂和结构破坏。移动冰丘导致桥墩变形破坏的三维有限元数值模拟能够为常年冻土区桥梁工程设计和地质灾害防治提供力学参数和科学依据。Migrating pingos formed along fault zone in permafrost north Tibetan Plateau, destructing bridge, culvert and oil pipeline. Here displacement and stress fields caused by migrating pingos and stresses of bended bridge pier were calculated by three dimensional finite element modeling based on field observation and laboratory tests, and breaking mechanism of bridge pier was analyzed after the numerical modeling. It is proved that expansion of migrating pingo can produce axis stress of 11 to - 21 MPa, formed concentration of stresses and caused evident displacement and deviation of bridge pier. The bending and deviation further result in extensional stress of 61.9 to 64. 6 MPa and compressional stress of -45.0 to -49. 0 MPa within the bridge pier, exceeding strength limit of the bridge pier. And stress concentration forms in size change area of upper bridge pier with maximum extensional stress of 26 to 30 MPa and maximum compressional stress of -25 to -28.8 MPa. The maximum extensional stress concentrated in size change area also exceeds strength limit of the bridge pier, formed shear-extensional fractures of the Chumaerhe Bridge. Three dimensional numerical modeling on migrating pingo destructing bridge pier can provide important factors for designing bridge and protecting geological hazard in permafrost.

关 键 词：移动冰丘 不均匀冻胀 桥墩 数值模拟 青藏高原北部 

分 类 号：P694[天文地球—地质学] P512.4