Stress measurement using rock cores around the ventilation shaft in Mizunami Underground Research Laboratory

Oikawa, Yasuki*; Soma, Nobukazu*; Tosha, Toshiyuki*; Matsui, Hiroya ; Tanno, Takeo; Hirano, Toru*

Acoustic Emission / Deformation Rate Analysis method (AE/DRA method) is a stress measurement method that uses test pieces cut from a drilled rock core. These test pieces are examined in a laboratory with cyclic-loading tests to measure stress along an axial direction in the original rock mass. We have conducted a basic research on a simple and low-cost estimation method to characterize the rock within the excavated damage zone using data from the investigation with a borehole (including drilling) most effectively. Here, we conducted AE/DRA stress measurement using rock cores provided from the Mizunami underground research laboratory's gallery at -200 m depth. Measured each stress data were varied even if in a same direction but estimated 3-D directions of 1 located in EW(NW-SE)NS range. This generally matches to the hydrofrac stress measurement data conducted near the Mizunami laboratory. A lot of stress data obtained from AE/DRA method and a flexible stress inversion method cause to estimate stable 3-D stress fields.