Investigation on the formation mechanism of the decollement zone in the viewpoint of geomechanics

2015 Fiscal Year Final Research Report

• Project/Area Number: 25630200
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Geotechnical engineering
• Research Institution: Nagoya Institute of Technology
• Principal Investigator: Zhang Feng 名古屋工業大学, 工学(系)研究科(研究院), 教授 (70303691)
• Co-Investigator(Kenkyū-buntansha): Sakaguchi Hide 独立行政法人海洋研究開発機構, 数理科学・先端技術研究分野, 分野長 (10235145) ; Yamamoto Yuzuru , 数理科学・先端技術研究分野, 分野長代理 (10435753)
• Project Period (FY): 2013-04-01 – 2016-03-31
• Keywords: プレート境界断層 / デコルマ / プロトデコルマ / 動的荷重 / プレート沈み込み運動 / 数値実験 / AMS / SEM

Outline of Final Research Achievements

Based on the assumption that cyclic loadings may be a main reason for the formation of décollement, siltstone and remolded Fujinomori clay are tested with static/dynamic loads. Meanwhile, anisotropy of magnetic susceptibility (AMS) and SEM are also measured to check the changes of micro-structure of the tested specimen. It is found that no major fabric variation happened though deformation occurred due to cyclic loadings, which is exactly the same as the characteristics of décollement. Furthermore, the process of the oceanic plate subducting beneath into continental plate and the dynamic loading of earthquake are simulated by numerical tests to investigate their influence on décollement. It is found that, the simulated results are similar to the observed micro-structural characteristics of décollement. In other words, the repeated dynamic loading due to earthquake is apparently the main mechanism to form the décollement zone.

Free Research Field

地盤工学