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1990 Fiscal Year Final Research Report Summary

A study of residual strength and method for evaluating the stability of slopes

Research Project

Project/Area Number 01460237
Research Category

Grant-in-Aid for General Scientific Research (B)

Allocation TypeSingle-year Grants
Research Field 農業土木
Research InstitutionUNIVERSITY OF THE RYUKYUS

Principal Investigator

GIBO Seiichi  UNIVERSITY OF THE RYUKYUS.COLLEGE OF AGRICULTURE PROFESSOR, 農学部, 教授 (30045132)

Project Period (FY) 1989 – 1990
KeywordsLandslide / Residual strength parameter / Ring shear test / Clay fraction / Plasticity index / Smectite / Residual factor / Safety factor
Research Abstract

In evaluating the stability of landslide, it is important to clarify the characteristics of residual strength of materials in the slip surface zone. The residual strength is the minimal shear strength along the surface where clay particles are finally oriented. The magnitude of the minimal shear displacement that is needed to attain to the residual state depends on the clay particle property and the normal effective stress. The magnitude of displacement as long as 40-60 cm for mudstone and 200-300cm for gravelly tuffaceous soil were required. A ring shear test is an effective method to attain the residual state, although long time is required due to the large-displacement shearing and the drained conditions.
Residual strength parameter is closely connected with the physical and mineralogical characteristics in landslide soils. It is concluded that clay fraction, plastisity index and amount of smectite appear to be a useful guide to estimate the residual strength parameter, and that furt … More her examination of the matter is warranted.
Back-analyzed strength parameters were not capable of predicting stability of landslide-prone slopes. The proposed method that incorporates a combination of back-analysis, residual and peak strength parameters, residual factor, safety factor and the Mohr-Coulomb's equation makes it possible to conduct a large scale stability evaluation.
The method for calculations of strength parameters are featured by the followings: (1) Laboratory strength parameters are incorporated into the evaluation for soil mechanical validity. (2) The standard slice method, a method used in back-analysis for safety factors, is introduced. (3) Two parameters of residual and peak strengths are incorporated into the expression after residual factors are introduced. (4)The type of slides and the condition of slip surfaces are taken into considerations.
Calculations of safety factors through the estimated residual factor are believed to be effective in determining safety factors of those landslide-prone slopes in dormant state, particularly of those found in areas where many landslide blocks are being spread out, some of which are actually undergoing slides. Less

  • Research Products

    (8 results)

All Other

All Publications (8 results)

  • [Publications] Seiichi Gibo・Keizo Sasaki: "Simple method for evaluating the stability of slopes" Proc.6th Int.Conf.and Field Workshop on Landslides,University of Milan. 157-165 (1990)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 宜保 清一・江頭 和彦 佐々木 慶三・吉沢 光三: "地すべり土塊のせん強度と斜面安定度評価ー牧野地すべりを例としてー" 土と基礎(土質工学会誌). 38巻(12号). 35-40 (1990)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 宜保 清一・江頭 和彦 林 義隆: "地すべり土の残留強度の大変位せん断試験による測定法と物理的鉱物学的性質による類推法" 農業土木学会論文集(印刷中). 159号. (1992)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 宜保 清一・江頭 和彦: "沖縄,島尻層群泥岩試料の残留強度と粘土粒子配向の関係" 農業土木学会論文集(投稿中).

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Seiichi Gibo. Keizo Sasaki: "Simple method for evaluating the stability of slopes" Proc. 6th Int.Conf.and Field Workshop on Landslides, University of Milan. 157-165 (1990)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Seiichi Gibo.Kazuhiko Egashira Keizo Sasaki.Mitsuzo Yosizawa: "Shear strength of landslide clay and evaluation of slope stability -A case study of Makino Landslide in Niigata-" Tsuchi-to-Kiso,JSSMEF. 38(12). 35-40 (1990)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Seiichi Gibo.Kazuhiko Egashira Yoshitaka Hayashi: "Measurement of residual strength of slip-surface soils with a ring shear apparatus and its relation to physical and mineralogical properties of the soils" Trans.JSIDRE. 159. (1992)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Seiichi Gibo.Kazuhiko Egashira: "Relation between reorientation of clay particles and the residual strength mudstones of the Shimajiri Group" Trans.JSIDRE.

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 1994-03-03  

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