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Earthquake induced deformation and failure of soft sediments

Research Project

Project/Area Number 10640440
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field Geology
Research InstitutionYamaguchi University

Principal Investigator

MIYATA Yuichiro  Univ., Fac.Sci., Assoc.Prof., 理学部, 助教授 (60253134)

Project Period (FY) 1998 – 2000
Project Status Completed (Fiscal Year 2000)
Budget Amount *help
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 2000: ¥100,000 (Direct Cost: ¥100,000)
Fiscal Year 1999: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1998: ¥1,400,000 (Direct Cost: ¥1,400,000)
Keywordsstrain rate / argillaceous sediments / earthquake / progressive failure / vein structure / reccurrence period / Nishizaki Formation / hypocenter / 歪み速度 / 平面歪み圧縮試験 / 歪みの局所化 / 三軸圧縮試験 / 間隙水圧
Research Abstract

The deformation and failure of soft sediments induced by earthquakes were experimentally investigated with special reference to (A) high strain-rate and (B) repeated inversion of shearing. The following results are demonstrated ;
(A) As increasing strain rate from 10^<-3> to 10^0/s, (1) shear strain is not localized, and homogeneously deformed, (2) change from limited progressive failure to simultaneous failure, (3) angle of shear plane (α) decrease from 70°to 50°, and (4) shear strength becomes larger. In these results, relationship between (3) and (4) contradict with each other in the sense of mechanics. In general, higher shear strength means higher internal friction as well as larger angle of shear plane (α). However, these results from plane-strain shear tests seems contrary to usual cases. As one reason, it was suggested that the effective stress between particles is reduces due to high pore pressure. (5) Regardless of strain rate, the amount of pore pressure is almost equal. Therefore, the expected high pore pressure under high strain rate was not realized. (6) Under strain rate less than 10^<-3> s^<-1>, angle of shear plane does not change.
(B) Minor fracture array was formed under low strain by repeated inversion of shearing, which is geometrically equivalent to the vein structures found in argillaceous sediments of active plate margin. (1) They are initiated as a conjugate Riedel shear under simple shear before failure with major Riedel shear ; (2) They grow with repetition of stress inversion ; (3) Higher void-ratio and low strain are preferable conditions. (4) The aspect ratio of the shear plane, height to spacing, is controlled by the width of the shear zone.

Report

(4 results)
  • 2000 Annual Research Report   Final Research Report Summary
  • 1999 Annual Research Report
  • 1998 Annual Research Report
  • Research Products

    (6 results)

All Other

All Publications (6 results)

  • [Publications] 田中尚,宮田雄一郎: "高速せん断による泥質堆積物の流動変形"地質学雑誌. 105巻. 352-363 (1999)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] 姉川学利,宮田雄一郎: "未固結砂泥互層における流体の移動過程-宮崎県日南層群の砂泥互層中にみられる流体噴出構造-"地質学雑誌. 107巻(印刷中). (2001)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] Hisashi TANAKA and Yuichiro MIYATA: "Flow deformation of argillaceous sediments under high strain rate shear."Jour.Geol.Soc.Japan. 105, (5). 352-363 (1999)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] Takanori ANEGAWA and Yuichiro MIYATA: "Fluid migration through unconsolidated layered system Fluid injection structures in alternated sandstone and mudstone layers of the Nichinan Group, Miyazaki Prefecture, Japan."Jour.Geol.Soc.Japan. 107, (4)(in press). 352-363

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] 姉川学利,宮田雄一郎: "未固結砂泥互層における流体の移動過程-宮崎県日南層群の砂泥互層中にみられる流体噴出構造-"地質学雑誌. 107巻・4号(印刷中). (2001)

    • Related Report
      2000 Annual Research Report
  • [Publications] 田中尚、宮田雄一郎: "高速せん断による泥質堆積物の流動変形"地質学雑誌. 105巻5号. 352-363 (1999)

    • Related Report
      1999 Annual Research Report

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Published: 1998-04-01   Modified: 2016-04-21  

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