Mechanism analysis of earthquake damage to pile foundations due to characteristic micro landform of plains in Japan

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K06566
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Building structures/Materials
• Research Institution: Chiba University
• Principal Investigator: Nakai Shoichi 千葉大学, 大学院工学研究院, 名誉教授 (90292664)
• Co-Investigator(Kenkyū-buntansha): 関口 徹 千葉大学, 大学院工学研究院, 准教授 (50451753) ; 中川 博人 国立研究開発法人建築研究所, 構造研究グループ, 研究員 (80713007)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 地震被害 / 建物 / 杭基礎 / 微地形 / 不整形地盤 / 有限要素解析 / 地震観測 / 東北地方太平洋沖地震

Outline of Final Research Achievements

Due to the 2011 Tohoku Earthquake, a number of buildings have suffered from damage to pile foundations. Among those, a characteristic damage pattern was found in that only one of many similar size buildings in the same site has suffered from pile damage, while other buildings have seemingly survived. Since these sites are situated in the middle of narrow river valleys, the effect of so-called alluvial valley was suggested. In order to clarify this hypothesis, a series of measurements and analyses have been carried out. It was found from the study that due to this irregular ground condition there is a possibility of a building located at the center of a site experiencing larger pile response compared with surrounding buildings when the site is situated in the middle of a narrow river valley. It was also found that this phenomenon is more evident in the case of shaking in the direction parallel to the longitudinal direction of the valley.

Free Research Field

地震工学

Academic Significance and Societal Importance of the Research Achievements

日本では地形が細かく変化することから、不整形地盤（平行成層ではない構造を有する地形・地盤）構造が多いと言える。国内外で、古くから不整形地盤の震動特性に関する研究が行われており、解析的な検討や地震観測記録の検証がなされている。しかしながら、不整形地盤に建つ建物群の地震被害分布に着目した検討はこれまでに知られていない。本検討は、典型的な不整形地盤である沖積谷地盤により、建物群のごく一部、しかも中央部に位置する建物のみに地震被害が集中する可能性を明らかにした最初の研究と考えられる。