Development of functional hybrid liquefaction countermeasure using composite improvement body that can be economically applied to existing house

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K04253
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 22030:Geotechnical engineering-related
• Research Institution: Nagoya Institute of Technology
• Principal Investigator: Morikawa Yukihiro 名古屋工業大学, 工学(系)研究科(研究院), 助教 (20710239)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 液状化対策 / 浮き型格子状地盤改良 / 排水性改良体 / 複合型改良体 / 過剰間隙水圧消散工法 / 排水ドレーン / 既設構造物 / 戸建て住宅

Outline of Final Research Achievements

In this study, floating grid type improvement method with a functional hybrid liquefaction countermeasure using composite improvement body with drainage improvement on top of an impermeable improvement was investigated as an economical and effective liquefaction countermeasure for existing houses. As a result of the study, it was found that the shear strength of the soil with drainage drains was maintained during liquefaction at a certain distance from the drain (about half the distance from the drain to the depth), and that the liquefaction strength increased significantly with each vibration. It was also found that the use of composite type improvements in floating grid type improvement increases the effectiveness of liquefaction countermeasure, and that even when only shallow parts of the wall are replaced with drainage improvements, significant countermeasure effects can be obtained depending on the shaking history.

Free Research Field

地盤工学

Academic Significance and Societal Importance of the Research Achievements

本研究によって，排水ドレーンを設置した地盤では加振履歴に応じて地盤強度が飛躍的に上昇したり，ドレーンの有効範囲が上昇したりするなど，これまで見過ごされてきた排水ドレーンの新たな効果が明らかとなった．さらに，本研究が提案している従来の地盤改良工法を想定した不透水性改良体の上部に排水性改良体を組合わせた複合型改良体，そしてそれを用いて既設住宅の周囲を囲う浮き型格子状地盤改良は，液状化時における住宅の沈下被害に加え，傾斜被害までも大きく抑制できることが明らかとなった．従って，本研究成果は既設住宅にも経済的に適用可能な液状化対策の可能性を示し，国土強靭化に大きく貢献できると考えられる．