An elasto-plastic theory for formation of stick-slip and failure in decollement zone under the deep seabed

2017 Fiscal Year Final Research Report

• Project/Area Number: 16K14305
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Geotechnical engineering
• Research Institution: Kobe University
• Principal Investigator: IIZUKA Atsushi 神戸大学, 都市安全研究センター, 教授 (40184361)
• Co-Investigator(Kenkyū-buntansha): 竹山 智英 神戸大学, 工学研究科, 准教授 (00452011)
• Project Period (FY): 2016-04-01 – 2018-03-31
• Keywords: デコルマ帯 / 粘土鉱物の変質 / 地盤力学 / 弾塑性構成式 / 土／水連成解析 / アスペリティー / スロースリップ地震 / 海溝型地震メカニズム

Outline of Final Research Achievements

In this study, we developed an elasto-plastic constitutive model considering the alteration from smectite to illite of clay minerals for the surface layer of the sliding part of the decollement zone, and incorporated it into the soil / water coupling system. Numerical simulation was carried out in the case where the decollement zone alters while receiving shear stress assuming plate subduction. The occurrence of excess pore water pressure accompanying alteration of clay minerals was in good agreement with the fact observed near the decollement zone. In addition, it was found that such alteration of clay minerals brings over-consolidation to the decollement zone and results in strain softening during shearing. This is consistent with the mechanism that sticking occurs in the decollement zone and an earthquake occurs slowly.

Free Research Field

地盤工学