Investigation on Lifeline fragility and disaster mitigation methods related to surface fault rupture during the chi-chi Earthquake

对考虑地下土体结构三维变化的三维地基模型进行了动力分析。该模型被认为是分析强地震动和活动断层附近位错的有效方法。用观测到的加速度记录得到的群延迟时间指数来建模相位特性。结果表明，群延迟时间的平均值随震中半径的变化而变化，群延迟时间的标准差受破裂指向性的影响。利用许多观测到的加速度记录，得到了任意两点上最大加速度比值的平均值和标准差，以检验一次地震的最大加速度的变化。标准差与两点间距离的对数成正比。在基岩断层位移作用下，利用模型土层对地表的位错进行了实验研究。结果表明：软土层上盘存在剪切带，硬土层上盘存在剪切带；采用壳有限元法分析了某故障穿越管道的性能。计算结果表明，当管道与断层破裂线的夹角大于90°时，管道与断层破裂线的夹角对管道的性能有重要影响。采用壳有限元法进行参数化研究，得到了三种不同横角下管道最大应变的设计公式。介绍了现有的管线穿越故障的对策，并根据新的设计公式提出了几种对策。结果表明，对于大的断层位移，除了硬件对策外，还需要软件对策。

Dynamic analyses for 3-D ground model considering 3-D variation of underground soil structures have been performed. This model is considered to be effective in analyzing strong ground motions and dislocation in the vicinity of active faults.A phase characteristics is modeled by using an index of a group delay time obtained by observed acceleration records. Results show that an average of the group delay time changes depending on a radius from an epicenter and the standard deviation of the group delay time is affected by the directivity of rupture.An average and standard deviation of a ratio of the maximum acceleration at arbitrary two points are obtained using many observed acceleration records to check the variation of the maximum acceleration for one earthquake. The standard deviation is turned out to be proportional to the logarithm of separation distance between two points.A dislocation of ground surface is experimented by using model soil layer under fault displacement at a base rock. The results show that a shear zone occurs both at upper hanging walls for soft soil layer, but only hanging wall for hard soil layer.Performance of a fault crossing pipeline is analyzed by a shell FEM. Computational results show that a cross angle between pipeline and fault rupture line gives an important effects to the behavior when the cross angle is more than 90 degrees.By carrying out a parametric study by employing the shell FEM, a design formula for the maximum pipe strain is obtained for three different cross angles.Existing countermeasures for pipelines crossing faults are introduced and also, several countermeasures are proposed based on the new design formula. It turned out that software countermeasures are required for large fault displacement, besides hardware countermeasures.