Reduction for seisic damages and evaluation of aseismic investment for lifeline system

为了减少强地震动对管道的破坏，研究了地基改善方法对液化表面层和埋地管道响应的影响。建立地震中和地震后生命线网络系统有效投资的评价方法也是本研究的目的。首先，重点研究了土壤液化引起的沉降等地面大变形，建立了埋地管道及其接头的地震响应分析方法。开发了基于潜在水头法的液化地面沉降二维有限元分析程序。结合压实法模拟程序、液化分析程序和地面沉降分析程序，分析了地面沉降作用下管道的响应。数值计算结果表明，采用压实改进方法可以有效地减小地表地层和管道的响应。其次，提出了未来地震条件下生命线网系统最优投资的评估方法。该方法采用蒙特卡罗模拟技术计算了生命线系统的可靠性，并对生命线的抗震投资进行了评估，包括管道加固和地面改造的初始成本、损坏管道的更新成本和工业损失。并对快速恢复的可选决策成本进行了研究。对熊本市供水系统进行了数值计算。结果表明，按成本最小的环节进行抗震加固的恢复策略对减少工业损失和缩短恢复时间是有效的。

Objects of this study is to investigate the effect of the ground improvement method on the responses of liquefied surface layers and the buried pipeline for reducing damages of pipeline during strong ground motion. It is also the object of this study to develop the evaluation method for effective investment for lifeline network system during and after earthquakes.Firstly we focus on the large ground deformations like subsidence induced by soil liquefaction and build up the analytical method for seismic response of buried pipeline including its joints. We develop the 2D FE analysis program for the ground subsidence induced by liquefaction based on the potential head method. Combining the programs for the simulation of the compacting method, the liquefaction analysis and the analysis of the ground subsidence, the responses of pipeline subjected to the ground subsidence are analyzed. The numerical computational results show that the compacting improvement method is effective to reduce the responses of the surface ground layers and the pipeline.Secondly we develop the evaluating method for the optimal investment for lifeline network systems subjected to future earthquakes. In proposed method the reliability for the lifeline system is computed by Monte Carlo simulation technique, then aseisimc investment for lifeline is evaluated including the initial cost for strengthening of pipes and ground improvement, renewal cost for damaged pipes and the industrial loss. Also the cost of optional decision for fast restoration is investigated. Numerical computations are conducted for the water supply system in Kumamoto city. Result shows that the restoration strategy for performing the aseismic reinforcement in order of least costed link is effective on reducing the industrial loss and shortening of the recovery.