不飽和火山灰質砂質土の液状化機構について  [in Japanese] LIQUEFACTION MECHANISM OF UNSATURATED VOLOCANIC SANDY SOILS  [in Japanese]

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Abstract

火山灰質砂質土で構成された斜面や盛土が,泥流状に崩壊する地震時地盤災害が発生している.本研究では,不飽和の火山灰質砂質土を対象として,同じ乾燥密度で異なる初期水分状態を持つ供試体に対し,間隙空気圧,間隙水圧,供試体体積変化を計測した非排気非排水条件下での繰返しせん断試験を行っている.その結果,緩い火山灰質砂質土は,飽和度が75%程度であっても,繰返しせん断によってサクションが低下すると同時に初期の有効応力を失い,いわゆる液状化状態になることを示した.また,実験結果を基に,不飽和土の液状化機構について考察し,不飽和土が繰返しせん断によって有効応力が失われるか否かは,土の間隙比と飽和度から決まる空気体積と土粒子骨格間隙の体積圧縮可能量に依存することを示した.

Mudflow type failures of natural slope and artificial fill composed of volcanic sandy soil occurred during past earthquakes. In this study, the results of cyclic tri-axial tests of unsaturated volcanic sandy soil measuring pore air pressure, pore water pressure and volume change of soil are reported. Tests are conducted for specimens with various initial suctions and the same dry density under undrained condition both for pore air and pore water. Loose volcanic sandy soil specimen subjected to cyclic shear lost effective stress even if the degree of saturation was about 75%. Based on the test results, the liquefaction mechanism of unsaturated soil was discussed. It was concluded that the fluidization potential depended on the degree of saturation (initial water retention condition) and volume compressibility of the soil.

Journal

  • Doboku Gakkai Ronbunshuu C

    Doboku Gakkai Ronbunshuu C 62(2), 546-561, 2006-07-20

    Japan Society of Civil Engineers

References:  30

Cited by:  4

Codes

  • NII Article ID (NAID)
    10019322205
  • NII NACSIS-CAT ID (NCID)
    AA12131726
  • Text Lang
    JPN
  • Article Type
    Journal Article
  • Data Source
    CJP  CJPref  J-STAGE 
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