Rock mass property evaluation based on the borehole wall images taken by using an ultrasonic scanner (USS)

Otsuka, Yasunori*; Ishikawa, Takanori*; Tajima, Katsuhiro*; Wada, Tetsu*; Aydan, mer*; Tokashiki, Naohiko*; Sato, Toshinori  ; Aoyagi, Kazuhei  

Ultrasonic wave reflection intensity of the wall of borehole drilled from bottom of the East Access Shaft in the Horonobe Underground Research Laboratory, Hokkaido, Japan, was obtained using an ultrasonic scanner (USS). In this paper, we compared results of USS observation with core logging data including core observation, optical digital scanner (ODS) observation, and result of Needle Penetration Index (NPI) tests. The results indicated that ultrasonic wave reflection intensity had a good correlation with other observation results. USS observation and NPI tests are useful techniques for determination of detailed rock mass classification.