Departmental Bulletin Paper 2016年熊本地震における熊本市上水道施設管路の被害分析

片桐, 信  ,  大西, 裕也

In this paper the damage of water distribution pipelines of Kumamoto city during the 2016 Kumamoto earthquake is investigated. The authors could have an opportunity to review the repair ledger of 240 pipeline’s damage locations. And they plotted the damage locations on the ground condition map exposed by the Geographical Survey Institute. From review of pipeline’s damage photographs, the main mode of damages was considered to be pulled out of pipe joints regardless of pipeline’s materials. Also, from the distribution of pipeline’s damage, three damage concentration areas were found. In these areas the surface ground is covered with soft soil, and traces of soil liquefaction were also found. In the Guidelines for Seismic Design Method of Water Supply Facilities 2009 published by the Japan Water Works Association, ground strain apply to buried pipelines were amplified in soft ground areas such as flood plains, back swamps, bottom plains and alluvial fans In the liquefaction areas, the ground strain is set to be higher taking account of permanent ground deformations. Therefore, the pipeline’s damage features obtained from this investigation considered to match the current seismic design guideline.

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