【作者】 刘爱文；

【导师】 胡聿贤； 赵凤新；

【作者基本信息】 中国地震局地球物理研究所 ， 地震工程学， 2002， 博士

【摘要】 本文首先介绍了埋地管线在断层作用下的震害，特别是以往震害资料极少的聚乙烯(PE)管在1999年集集地震中通过断层的破坏情况。根据震害资料，本文归纳总结了埋地连续管道的各种破坏模式。接着，本文回顾了现有的埋地管子在断层作用下的分析方法并指出其有待改进的地方。现有的理论分析方法和梁模型有限元方法都难以分析管截面发生大变形的情况，例如屈曲变形。现有的壳模型有限元方法虽然可以分析管截面中的大变形情况，但是，由于在断层作用下受影响的管子的范围比较长，需要耗费大量的计算时间。另外从现在国际上埋地管线的抗震设计规范发展方向来看，人们不再满足于过去的弹性设计从而推出了塑性设计，继而提出极限状态设计(性能设计)的观点。现在的抗震规范和有关研究中，还很少有估计大变形时管子内的应力应变的方法，虽然2000年高田至郎等人基于壳有限元模型的参数研究提出了设计用的简化计算公式，但在他们的分析模型中存在一些问题有待改进。 根据以上的研究背景，本论文采用壳模型有限元方法对管子在断层作用下的地震反应进行了分析。用壳单元对管子进行建模同梁单元相比可以更好地分析管截面的大变形情况。为了解决现有的壳单元方法需要大量计算机时的缺点，本论文首次从理论上把离断层较远管土之间相对变形较小的管子直线段部分的变形等效为一个非线性弹簧，将此等效边界引入到有限元模型中，使得模型中的壳单元部分主要用来分析我们所感兴趣的在断层附近发生大变形的管段，从而达到节约计算时间的目的。比较其他壳分析方法所需的计算时间，本文引入等效边界后的壳模型所需的计算时间最短，高田至郎等的壳和梁单元混合模型为其次，固定边界模型需要的时间最长。 在以往研究埋地管子在断层作用下反应的方法中，一般考虑的是断层两侧为相同场地条件、管线在断层两侧变形为反对称的情况。但是在埋地管线通过断层的实际震害和不均匀沉降实验中，都可以发现管线发生非对称变形的现象。所以在本文提出的壳模型中对这种现象给以了特别的关注。通过设定断层两侧的横向土弹簧参数不同，本文所提出的壳模型可以很好地模拟这种管子发生非对称变形的情况。利用本文所提出的壳有限元模型，对两类埋地管道通过断层的实际震害进行了模拟：第一类是在供水管网系统中占据重要位置的大口径钢管的震害，土耳其地震和集集地震分别都有这类管子的震害；第二类是以往震害资料很少的PE管在集集地震中的震 害。在模拟钢管和PE管的震害中，又分别对比了断层两侧士弹簧刚度相同和不同的 两种情况。 在模拟土耳其地震大口径钢管的震害中，本文壳模型的分析结果与Eidinger的梁 单元模型比较，可以更清楚地解释管子第三处破坏产生的原因。本文壳模型得到的 管子内的最大压缩应变值 （2．4％）较之梁单元模型（9．7％）也更符合管子屈曲变 形的实际程度。另外，本文壳模型计算得到的三处破坏点的压缩应变大小顺序（从 大到小依次为B、A、C）也符合现场所观察的各点破坏程度，而Eidinger的梁模型 得到A点的应变值最大，与实际震害现象相矛盾。这表明本文的壳模型较之梁单元 模型能够更好地模拟埋地管线震害。 本文探讨了管子作为一个中空圆柱壳体在断层作用下非线性反应的大变形表现 形式。对于0＼p三90”的情况，当断层位移相对管径还不是很大时（管子内的弯曲应 变与轴向拉伸应变相差不大的情况），断层附近管子变形形式与梁相似；当断层位移 相对管径很大时（管子以轴向拉伸应变为主的情况），断层附近的管子轴线变形为一 圆弧，管子表现得像一条没有弯曲刚度的索。这说明Kennedy方法和王汝粱等人提 出的梁理论方法在一定条件下对管子的变形假设是成立的，但是这两种理论方法所 得到的管子反应的应变值远小于壳单元方法的结果。这是因为在周围土压作用下管 截面还会发生椭圆化变形或者屈曲变形。现有的梁理论方法得到的结果偏小，本文 发现在进行管截面变形（椭圆化变形或者屈曲变形）修正之后可以得到管于应变的 真实值。 通过本文的分析还发现：既使是在与断层交角为90度的情况下，断层位错足够 大时管子会在断层相交处发生塑性应力集中现象，最终在该处发生拉伸破裂。当管 子与断层的交角大于90度时，压缩应变主导着管子的变形。管于在断层两侧的屈曲 处分别形成一个塑性铰，两个塑性铰之间的管段表现近似为一刚性杆，随着断层位错 增大在土体中发生转动。参数研究表明90度角为管子通过断层的最佳角度，以较大 的口径、较厚的管壁、埋设在较软的场地中为管子通过断层的最佳条件。 由于实际中针对每一个通过断层的管子做三维的壳模型有限元分折是颇更多还原

【Abstract】 Firstly, the study of damage of buried pipelines crossing faults is introduced in the first chapter, specially for the damage of PE gas pipeline in 1999 Ji-Ji earthquake, because these kinds of direct evidences of fault ruptures on PE pipe failures were rare in the past. In general, the failure mode of buried pipeline under the fault movement can be divided into two types: (A) Necking Failure, caused by tensional deformation when the crossing angle β is less than 90°; (B) Buckling Failure, caused by compressive deformation when the crossing angle β is larger than 90°. Next, this paper systematically reviews several simplified design methods that have been proposed to obtain the maximum stress or strain in pipelines crossing an active fault. Usually, the buried pipeline is modeled as cable, beam or shell model in these methods. There are the two limitations for both of the cable method and beam method: (1) It can only analyze the response of pipeline under tensile loading (β<90). When the crossing angle is larger than 90 degree, the pipeline would prone to suffer a buckling damage; (2) It cannot be used to analyze the large deformation in the pipe section. Since it is difficult for the cable or beam model to consider the large deformation in the pipe crossing section, the FEM analysis with shell element has been proposed to investigate the response of pipe. Takada (2000) proposed a simplified design formula to obtaining the maximum strain in steel pipes based on the parametrical study using a beam-shell hybrid FEM.To extend Takada’s shell method, a 3-dimension shell-spring FEM is proposed to analyze the response of steel pipelines under the large fault movement in the second chapter. Soil springs are used around the pipe including vertical, lateral and axial soil springs to consider the interaction between the pipeline and the surrounding soil. The pipe segment near fault that usually suffers large deformation is modeled with a plastic shell element in order to consider the effect of local buckling and section deformation. To reduce the calculating time of the whole model, an equivalent spring proposed by the author is applied at two ends of the shell model.Compared with other analytical FEM models, it is easy for this model to consider the situation when the soil conditions on the both side of the fault are different ( Kl ≠ K2). In the third chapter, the performance of two fault-crossing steel pipelines with large diameters (Φ2.0 m and Φ2.2 m) at fault crossing in Kocaeli Earthquake and Ji-Ji Earthquake are studied. Thames water pipe (Φ2.2 m) suffered three damages along the pipeline asymmetrically spaced around the fault in Kocaelie earthquake, and the Shigang water pipe (Φ2.0 m) suffered two damages along the pipeline symmetrically spaced around the fault in Ji-Ji earthquake. The failure performance of these two damage cases for large diameter steel pipelines are much different form each other because of the different types of fault movements as well as the type of soil condition on both sides of fault (Kl ≠ K2 and Kl = K2). Compared with the beam model, the shell-spring model proposed in this paper can examine the failure mode of a buried pipeline under the fault movement more clearly. The occurrence of the third damage in Thames water pipeline is specially discussed in Chapter 3. Considering different soil spring models for vertical fault movement and horizontal fault movement, two damage cases of PE pipeline in Ji-JiEarthquake have also been simulated.The large deformation of a buried pipeline under fault movement is investigated in the 4th chapter. To examine the inelastic behavior of buried pipelines, the parametric studies on pipe material property, diameter (D), diameter-to-thickness ratio (D/t), crossing angle (β), as well as soil stiffness, have been conducted using a shell-spring FEM method. For each parametric study case, the fault displacement (A) is up to 7 meters. Through the parametric studies, the inelastic behavior of a buried pipeline differs so much from that of the beam更多还原