Fundamental study on evaluation of an excavation disturbed zone by measurement of stress using cores and measurement of vibration caused drilling (Joint research)

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

JAEA-Research 2010-048, 45 Pages, 2011/02

JAEA-Research-2010-048.pdf:7.68MB

In excavating a gallery or a shaft in deep underground, an excavation disturbed zone (EDZ) develops around the opening with new cracks due to both stress redistribution and excavation induced damage. The investigation and the evaluation of an EDZ are needed because the changes in rock properties and the EDZ development influence performance assessment of geological disposal and design of the underground structures. However, the in situ investigation of an EDZ is time consuming and costly because investigations are large-scale and required specialized equipment. We conducted a fundamental study for the development of an EDZ investigation method that is easy and inexpensive using the information obtained from only drilling. This report describes the results of the joint research carried out in fiscal year 2008 and fiscal year 2009. In Chapter 1, we provide the overview and the background of this study. In Chapter 2, we discuss the estimation of stress state around the research gallery at a depth of 200m in Mizunami Underground Research Laboratory (MIU) by Acoustic Emission / Deformation Rate Analysis (AE/DRA) method using rock cores obtained from the drilling. In Chapter 3, results of the evaluation of geological structure around the research gallery at a depth of 200m in MIU based on Seismic While Drilling (SWD) method using the vibrations caused by the drilling are described.

Evaluation of geological structure by means of seismic signal while drilling rock core in the deep shaft

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

no journal, , 

no abstracts in English

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*

no journal, , 

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.