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活动断裂附近强地面运动和位错的有效模型。利用观测的加速度记录获得的群延迟时间指数来模拟A相特征。结果表明，群延迟时间的平均值随距离震中半径的变化而变化，群延迟时间的标准差受破裂的方向性影响，利用大量的观测加速度记录，得到任意两点的最大加速度之比的平均值和标准差，以检验一次地震的最大加速度的变化。标准差与两点间距的对数成正比。利用基岩断层位移下的模型土层进行了地表错动实验。结果表明，软土层上悬挑墙处均存在剪切带，而硬土层仅在上悬挑墙处出现剪切带。计算结果表明，当管道与断层断裂线的交叉角大于90°时，管道与断层断裂线的交叉角对管道的行为有重要影响，通过壳体有限元进行参数研究，得到了三种不同交叉角下管道最大应变的设计公式，介绍了管道跨断层的现存对策，并根据新的设计公式提出了几点对策。结果表明，对于较大的故障位移，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.