Application and integrated evaluation of the compact conical-ended borehole overcoring technique in a fractured rock

Toshinori Nayuki, Tatsuya Tanaka, Kenichi Ando, Koji Oka, Naoki Nishizaka, Yuichiro Shimoguchi, Hiroshi Ogawa, Kazu Saito, Kiyotoshi Sakaguchi, Masaharu Ltamoto

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Several rock stress measurement techniques have been proposed by different research groups. Due to factors that cannot be visually confirmed, such as for instance rock type, geological structure and heterogeneity, the applicability and accuracy of the different measurement techniques can vary widely. Validation and engineering judgement with respect to the measured results is therefore necessary. This study focusses on the Compact Conical-ended Borehole Ovarcoring (CCBO) technique (Sakaguchi at al., 1994, 1995 and 1999), which is a stress relief method. With the CCBO technique, the three-dimensional stress field can be determined with a single measurement. Measurements can be carried out in a small zone and are therefore also applicable in fractured rock. In this study, in-situ stress measurement was conducted by the CCBO technique in a horizontal borehole drilled into a natural slope that is composed of fractured rock. In-situ stress measurements were performed at four measurement points in the borehole. To verify the applicability to the fractured rock of the CCBO technique, three-dimensional FEM numerical analysis of the topography based gravitational stress distribution was carried out separately in order to compare the results. Furthermore, a new evaluation method was developed to integrate the several measurements results in order to perform a more reliable assessment of the in-situ stress. Based on the results of the integrated evaluation method, in-situ stress values could be calculated that were highly consistent with the numerical analysis results.

Original languageEnglish
Title of host publicationISRM International Symposium on In-Situ Rock Stress, ISRS 2016
Editors Raasakka, Erik Johansson
PublisherInternational Society for Rock Mechanics
Pages593-599
Number of pages7
ISBN (Electronic)9789517586061
Publication statusPublished - 2016 Jan 1
EventISRM 7th International Symposium on In-Situ Rock Stress, ISRS 2016 - Tampere, Finland
Duration: 2016 May 102016 May 12

Publication series

NameISRM International Symposium on In-Situ Rock Stress, ISRS 2016
Volume2016-May

Other

OtherISRM 7th International Symposium on In-Situ Rock Stress, ISRS 2016
Country/TerritoryFinland
CityTampere
Period16/5/1016/5/12

Keywords

  • Compact Conical-ended Borehole Overcoring technique
  • Fractured rock
  • Integrated evaluation method
  • Three-dimensional FEM analysis

ASJC Scopus subject areas

  • Geophysics

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