Applicability of Core-based In-situ Stress Measuring Methods to Limestone Evaluated by Comparison with Conical-Ended Borehole Metho

Kiyotoshi SAKAGUCHI	Dr. Eng. Research Assoc. Department of Geoscience and Technology, Graduate School of Engineering, Tohoku University
Koji MATSUKI	Dr. Eng. Prof. Department of Geoscience and Technology, Graduate School of Engineering, Tohoku University
Kiyohiko OKUMURA	Dr. Eng. Research Assoc. Department of Geoscience and Technology, Graduate School of Engineering, Tohoku University
Takeshi TOKUMOTO	Tekken Co. Ltd.

J. of MMIJ, Vol.115, No.7, pp.517-524 (1999)

Three-dimensional in-situ stresses in a hard limestone lying about 700m below the surface were estimated by five core-based methods(ASR, DSCA, PSHA, DRA and AE method) and a stress relief method(Conical-ended borehole method; CEBM).

The confidence intervals of the results by CEBM were estimated, and then, the results by the core-based methods were compared to those by the CEBM to examine the reliability of the core-based methods for this particular rock.

The ASR method was difficult to estimate reliable in-situ stresses in this hard limestone whose Young's modulus ranged from 40GPa to 80GPa. A more accurate measuring system was required to apply ASR method to such a hard rock. The DSCA(OC), the PSHA and the DRA(Demax)(e) method estimated the in-situ stresses relatively consistent with those by the CEBM. The agreement of the results by both the conventional DRA and the AE method with those by the CEBM was poor for the rock.

KEY WORDS : Core-based method, Conical-ended borehole method, In-situ stress measurement, Limestone

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