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1992 Fiscal Year Final Research Report Summary

A study of dynamic strength of rock masses related to microcrack propagation.

Research Project

Project/Area Number 03452204
Research Category

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

Allocation TypeSingle-year Grants
Research Field 基礎・土質工学
Research InstitutionSaitama University

Principal Investigator

YOSHINAKA Ryunoshin  Saitama Univ. Engineering Prof., 工学部, 教授 (00008822)

Co-Investigator(Kenkyū-buntansha) OSADA Masahiko  Saitama Univ. Engineering Res. Assoc., 工学部, 助手 (00214114)
YAMABE Tadashi  Saitama Univ. Engineering Assoc. Prof., 工学部, 助教授 (40125894)
Project Period (FY) 1991 – 1992
KeywordsDYNAMIC STRENGTH / MICROCRACK / VISCOELASTICITY / SOFT SEDIMENTARY ROCK / PORE WATER PRESSURE
Research Abstract

The foundations of many important structures such as nuclear power plants are often composed of soft sedimentary rocks and subjected to cyclic loading caused by earthquakes and so on. Consequently the capacity of these foundations is required for the stabibility of those rocks under not only static but also cyclic loading.
The purpose of this research is to investigate the relation between static and dynamic strength, mechanism of failure under cyclic loading and viscoelastic properties of soft sedimentary rocks. First, the triaxial compression experiments and stepwise cyclic loading experiments were performed under consolidated and undrained conditions. Comparing the results of two kinds of experiments, we obtained that the ratio of dynamic strength to static strength in total stress expression is from 1.0 to 1.5 but 1.0 in effective stress expression. This means that it is only different in the behavior of pore water pressure.
Cyclic fatigue experiments were performed to investigate the behavior of pore pressure by every stress cycle. As a result, it is found that the behavior of pore pressure is systematically changed and that this change is described by two quantities, that is, the difference between maximum and minimum values in pore pressure caused by a stress cycle and a lag of phase difference on pore pressure cycles for stress cycles. It is thought that failure of rocks results from the brittle process involving the cumulative growth of internal cracks. We interpret that this behavior results from crack initiation and propagation. In fact, internal cracks, with orientations parallel to a maximum compression and ultimate fracture plane, were microscopically observed from rock specimens after failure.
In addition, stress relaxation experiments showed that the peaks of relaxation spectra dispersedly distributed, dependent on temperature. These results are very meaningful to establish the constitutive equations involving the effect of crack growth.

  • Research Products

    (8 results)

All Other

All Publications (8 results)

  • [Publications] 吉中 龍之進: "構造物の建設と岩盤工学" 土質工学会誌「土と基礎」. 40. 1-6 (1992)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 吉中 龍之進: "動的繰り返し荷重下における堆積軟岩の強度・変形特性" 第25回岩盤力学に関するシンポジウム講演論文集. 116-120 (1993)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] T,Yamabe: "Effect of anisotropy on three dimensional excavation analysis of jointed rock masses" Proc.of Int.Conf.on Numerical Methods in Geomechanics. 7. 455-460 (1991)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 吉中 龍之進: "ブロック理論と岩盤工学への応用(訳著)" 土木工学社, 359 (1992)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Rhunoshin Yoshinaka: "Rock engineering and practice." Tuchi-to-Kiso. Vol.40. 1-6 (1992)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Rhunoshin Yoshinaka, Masahiko Osada and Wataru Hori: "Strength and deformation characteristics of soft sedimentary rocks under cyclic loading." Proc. of the 25 th Symposium on Rock Mechanis. 116-120 (1993)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Tadashi Yamabe: "Effect of anisotropy on three dimensional excavation analysis of jointed rock masses." Proc. of Int. Conf. on Numerical Methods in Geomechanics. Vol.7. 455-460 (1991)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Ryunoshin Yoshinaka and Yuzo Ohnishi: Dobokukougaku-sya. Block Theory and its Application to Rock Engineering. (a translation), 359 (1992)

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

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Published: 1994-03-24  

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