大口径长输埋地管线断层响应行为及破坏机理研究

Permanent ground deformation induced by the fault movement is one of the main reasons why buried pipelines failure or destroy in earthquake, it is an inevitable reality in structural engineering that long-distance buried pipelines transporting oil and gas traverse fault region. It is a basis of seismic fortification for pipeline engineering to recognize exactly response behavior and failure mechanism for buried pipeline under fault movement. In this study, finite element model of pipe-soil system is developed including pipe and soil mass, discontinues contact and interaction behavior between pipe -soil are simulated by finite element model and discontinues deformation analysis (DDA) method,then force-deformation'relation between pipe and soil is developed .Mechanism and condition of strength failure or buckling failure for buried pipeline are recognized by studying response behavior for buried pipeline under fault movement and the influence of related parameters. Solutions to difficult problems, such as contact analysis of pipe-soil and so on , are provided by integrating discontinues deformation analysis (DDA) method. The purpose of this study is not only obtain cognition of response behavior and failure mechanism for buried pipeline under fault movement by elaborate modeling and analyzing, but also seek after feasibility of aseismic response analysis for buried pipeline by discontinues deformation analysis (DDA) method.

断层引起的地面永久大变形是埋地管线地震破坏的主要原因之一，而石油、天然气等长输埋地管线穿越断层区域是工程上无法避免的现实。正确认识断层作用下埋地管线响应行为和破坏机理是管线工程抗震设防的基础。本项目将大口径长输埋地管线和周围土体共同取出建立管土系统模型，采用有限元方法与非连续变形分析（DDA）方法相结合模拟管土界面的非连续性接触及管-土之间的相互作用，建立管-土间的作用力与相对位移之间的关系，为埋地管线抗震设计时弹簧参数的选取提供依据。同时研究断层作用下埋地管线的响应特征及参数影响，认识埋地管线发生强度破坏或者失稳破裂的机制和条件。引入非连续变形分析思想，结合有限元技术给出管土接触模拟等困难问题的解决方案。本项研究，一方面通过较为精细化的建模和分析获得穿越断层埋地管线响应行为和破坏机理方面的认识，另一方面也探索非连续变形分析方法用于解决埋地管线抗震分析等实际工程问题的可行性。

本课题主要针对跨断层大口径长输埋地管线在断层作用下的响应行为及破坏机理进行研究，以掌握其发生强度破坏或者失稳破裂的机制和条件，为埋地管线工程抗震设防提供依据。为此，本课题对跨断层大口径长输埋地管线进行研究，主要研究成果包括：(1)建立跨断层埋地管线-土体三维有限元分析模型。具体包括边界条件处理、断层作用施加、管道及土体本构模型的选取、管土接触面处理及有效计算区域确定，其中有效计算区域考虑了断层位错、管道埋深、径厚比及土体刚度等因素的影响。（2）从断层位错量、管线埋设深度、管道径厚比及场地条件等方面来分析管-土之间的非线性接触状态，即管土界面滑移及分离情况；分析管土之间的接触界面上的接触应力，即管土之间的相互作用。（3）根据建立的数值模拟方法，考虑管道直径及壁厚、周围土体特性、断层位错量、断层倾角、管道与断层夹角及管道埋深分析埋地管线在断层作用下的响应行为及管道屈曲问题，研究埋地管线发生强度与失稳破坏的机理和条件及其参数影响。