Shigen-to-sozai, Vol.116, No.12, pp.965-971.
Consideration on DSCA and AE Methods for
Stress Measurement by Comparing with Corediscing
Information and Others
Koichi SHIN1, Yasuki OIKAWA2 and Hisatoshi ITO3
| 1. Geotechnical & Earthquake Engineering
Department, Central Research Institute of
Electric Power Industry, Abiko-shi 270-1194 2. National Institute for Resources and Environment, 16-3 Onogawa, Tsukuba 305-8569 3. Geology Department, Central Research Institute of Electric Power Industry |
| Rock stress is of great interest in cavern
excavation, hot dry rock geothermal development
and others. At great depth technically and
economically usable methods for stress measurement
are not many, and it is not rare that only
methods based on laboratory core tests are
available or stress induced rock failure
phenomena like corediscing may give stress
information. Stress induced failure phenomena
like corediscing are straightforward information
about stress state in a rock. On the other
hand, core based methods have assumptions
in their principles to some extent and hence
they are not yet widely accepted. Whether
the core based methods become to be truly
reliable depends on the accumulation of the
comparisons to other clear stress indicators. This paper reports one of them. Corediscing was observed in a granite from 1,000 m depth at Akita pref., Japan. Test specimens for DSCA and AE methods were retrieved just adjacent to the discing point. Estimated rock stress state at the point were in agreement both in the maximum stress direction and the stress value with the corediscing criteria presented by Sugawara et al. and Matsuki et al. Also the spatial variation of stress state were observed in accordance with the structural condition of the rock. The average stress estimated by the core test was found to be in accordance also with shut-in pressure. Thus DSCA and AE methods were found to be basically reliable methods. The specimens were tested about 6 years after the coring at the geothermal region and gave reasonable estimate of rock stress. Therefore it is also said that the effect of heat and the time from core retrieving to test can be not significant. |
| KEY WORDS: DSCA, AE, Rock Stress, Corediscing, Two-Lines-Fitting Scan Method |