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Estimating Stress at Great Depth from Borehole Breakout

Research Project

Project/Area Number 09044120
Research Category

Grant-in-Aid for international Scientific Research

Allocation TypeSingle-year Grants
SectionJoint Research
Research Field 広領域
Research InstitutionTohoku University

Principal Investigator

HAYASHI Kazuo  Tohoku University, Institute of Fluid Science, Professor, 流体科学研究所, 教授 (30111256)

Co-Investigator(Kenkyū-buntansha) SONG Insun  University of Wisconsin, Faculty of Engineering, Research Assistant, 工学部, 研究員
SAITO Hiroyuki  Tohoku University, Institute of Fluid Science, Research Associate, 流体科学研究所, 助手 (70264091)
ITO Takatoshi  Tohoku University, Institute of Fluid Science, Associate Professor, 流体科学研究所, 助教授 (00184664)
HAIMSON Bezalel  University of Wisconsin, Faculty of Engineering, Professor, 工学部, 教授
BEZALEL Haim  ウィスコンシン大学, 工学部, 教授
Project Period (FY) 1997 – 1998
Project Status Completed (Fiscal Year 1998)
Budget Amount *help
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 1998: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1997: ¥2,000,000 (Direct Cost: ¥2,000,000)
KeywordsTectonic Stress / In Situ Measurement / Borehole Breakout / Rock Stress / Geothermal Energy / HDR / ブレイクアウト / 地圧
Research Abstract

The objective of the present study is to clarify the mechanism of nucleation of borehole breakout and to examine the growth process of the borehole breakout, emphasizing the effect of the bottom of the borehole. Firstly, the characteristics of the three-dimensional elastoplastic stress field around the bottom were studied by FEM analysis, paying special attention to the singular stress field around the bottom. Then, a model of a pseudo two-dimensional stress field simulating the three-dimensional stress field was constructed, and the growth process was examined by using the pseudo stress field. The results are summarized as follows :
1) Near the bottom of the borehole, stress concentration takes place at a circumferential position that is different from that at a borehole section far from the bottom. The region of stress concentration is very localized.
2) Thus, for a rock that is insensitive to a local stress field in fracture nucleation, borehole break out is not formed at the bottom of borehole.
3) Variation of the stress field with respect to the distance between the bottom and the observation position, can be seen as the time variation of stress at a fixed depth during drilling. The geometry of borehole breakout calculated by following exactly the loading path just mentioned is almost the same as that estimated by two-dimensional approach.
4) Therefore, the breakout can be considered to be formed on the wall of a cylindrical cavity in an elastoplastic medium subjected to a monotonically increasing load at infinity.
5) The width of the breakout is almost the same as that estimated by purely elastic stress state, indicating the validity of the hypothesis proposed by Haimson et al. on the relationship between the width and the far field stress.

Report

(3 results)
  • 1998 Annual Research Report   Final Research Report Summary
  • 1997 Annual Research Report
  • Research Products

    (12 results)

All Other

All Publications (12 results)

  • [Publications] 伊藤高敏: "ボアホールブレイクアウト形成プロセスの解析" 日本機会学会いわき地方講演会講演論文集. 31-32 (1997)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1998 Final Research Report Summary
  • [Publications] T.Ito: "Stress Concentration at the Bottom of a Borehole and its Effect on Borehole Breakout Formation" Rock Mechanics and Rock Engineering. 31・3. 153-168 (1998)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1998 Final Research Report Summary
  • [Publications] 伊藤高敏: "ボーリング孔掘削過程で起こる圧縮破壊のシミュレーション" 日本機会学会東北支部第34期総会講演会講演論文集. 発表予定. (1999)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1998 Final Research Report Summary
  • [Publications] 伊藤,高敏: "掘削プロセスを考慮したボアホールブレイクアウト形成過程の数値シミュレーション" 資源素材学会平成11年度春季大会講演予稿集. 発表予定. (1999)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1998 Final Research Report Summary
  • [Publications] T.Ito: "Growth Process of Borehole Breakout (in Japanese)" Proc.JSME Tohoku Regional Annual Meeting at Iwaki. 31-32 (1997)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1998 Final Research Report Summary
  • [Publications] T.Ito: "Stress Concentration at the Bottom of a Borehole and its Effect on Borehole Breakout Formation" Rock Mechanics and Rock Engineering. 31. 153-168 (1998)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1998 Final Research Report Summary
  • [Publications] T.Ito: "Simulation of Compressive Fracture During Drilling of a Borehole (in Japanese)" Proc.JSME Tohoku Regional Annual Meeting at Sendai. (to appear). (1999)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1998 Final Research Report Summary
  • [Publications] T.Ito: "Numerical Simulation of Growth of Borehole Break-out During Drilling (in Japanese)" Proc.MMIJ Annual Spring Conf.(to appear). (1999)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1998 Final Research Report Summary
  • [Publications] T.Ito: "Stress Concentration at the Bottom of a Borehole and its Effect on Borehole Breakout Formation" Rock Mechanics and Rock Engineerign. 31・3. 153-168 (1998)

    • Related Report
      1998 Annual Research Report
  • [Publications] 伊藤高敏: "ボーリング孔掘削過程で起こる圧縮破壊のシミュレーション" 日本機会学会東北支部第34期総会講演会講演論文集. (発表予定). (1999)

    • Related Report
      1998 Annual Research Report
  • [Publications] 伊藤高敏: "掘削プロセスを考慮したボアホールブレイクアウト形成過程の数値シミュレーション" 資源素材学会平成11年度春季大会講演予稿集. (発表予定). (1999)

    • Related Report
      1998 Annual Research Report
  • [Publications] 伊藤 高敏: "ボアホールブレイクアウト形成プロセスの解析" 日本機械学会いわき地方講演会講演論文集. 31-32 (1997)

    • Related Report
      1997 Annual Research Report

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Published: 1997-04-01   Modified: 2016-04-21  

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