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

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.