Shigen-to-sozai, Vol.118, No.5,6, pp.361-368.
The State of the Art of Rock Stress Measurement at Great Depth by Borehole Pressurization and the Points at Question
Yoshiaki MIZUTAa
| Professor, Dr., Faculty of Engineering, Yamaguchi University |
| The hydraulic fracturing technique as a method
for determination of in-situ stresses has
the advantage over other stress measuring
methods in that it can be used at considerably
greater depths from a point of access. This
is of great significance in earthquake regions
where stresses at hundreds or thousands of
meters are of interest. Despite of the increasing
use of hydraulic fracturing, however, there
are uncertainties associated with the interpretation
of the resulting data. In particular, confidence
in the calculated maximum principal stress
is less than in the minimum principal stress,
although the former is often of great moment.
Furthermore, the equation established to
calculate the maximum principal stress is
unclear. More recently, dry fracturing techniques
have been developed and examined as the new potential method for determination of in-situ stress at great depth, through studies both in the laboratory and in the filed. In dry fracturing, the borehole wall is subjected to shear load as well as normal load, which are induced by internal pressurization of the probe. The state of the art of rock stress measurement by hydratilic fracturing is reviewed and a comparative study is made of two kinds of dry fracturing techniques, which have been developed as the potential method for stress determination. The general review is followed by individual summaries of each method and the main characteristics of its validations and applications. |
| KEY WORDS: Hydrofracturing, Dry Fracturing, Stress Measurement, Great Depth, Validation Evaluation |