Aging effects on liquefaction resistance of sands and relevant index parameters

2018 Fiscal Year Final Research Report

• Project/Area Number: 16H04410
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Geotechnical engineering
• Research Institution: Ehime University
• Principal Investigator: Mitsu Okamura 愛媛大学, 理工学研究科(工学系), 教授 (50251624)
• Co-Investigator(Kenkyū-buntansha): 安原 英明 愛媛大学, 理工学研究科(工学系), 教授 (70432797)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 液状化 / 地震 / 液状化判定法 / 年代効果

Outline of Final Research Achievements

Repeated small shaking events due to earthquakes significantly enhance liquefaction resistance of soils. This study investigates the pre-shearing effects on the liquefaction resistance (RL) through laboratory tests and centrifuge tests. An attempt was made to explain the effects quantitatively with a single index parameter of the volumetric strain caused by pre-shearing. It was confirmed from triaxial tests that the RL of pre-sheared sand uniquely increased with increasing volumetric strain during the pre-shearing. To examine the pre-shaking effects on the RL of sand under a level ground condition, centrifuge tests were conducted. Sand models were subjected to small shaking events repeatedly, which were weak enough not to cause liquefaction. At the end of the test, the sand was subjected to a strong shaking event. The relationship between RL ratio of the ground and volumetric strain that occurred in the pre-shaking events coincides with that obtained from the triaxial tests.

Free Research Field

土木工学

Academic Significance and Societal Importance of the Research Achievements

現在で広く用いられている液状化判定法，すなわち地震時に地盤が液状化するか否かを予測する方法は過度の安全側の判定となるため，精度の向上が望まれている。地盤の液状化に対する抵抗力は，古い土ほど大きくなる（年代効果）ことが知られている。本研究では，年代効果を詳細に調べ，その影響を取り入れた液状化判定法を提案した。また，地盤の深部ほど（古い土ほど）液状化強度が増加するメカニズムもある程度明らかにした。