Seismic tomography investigation in 140m gallery in the Horonobe URL project

Sugita, Yutaka ; Nakamura, Takahiro; Sanada, Hiroyuki; Aizawa, Takao*; Ito, Shunichiro*

The creation of an excavation disturbed zone (EDZ) is expected around the gallery when the gallery is excavated in the underground to dispose the radioactive waste. In-situ EDZ experiment has been performed to determine the rock properties and width of the EDZ in 140m gallery at a depth of 140m below the surface at Horonobe URL. In the experiment, seismic tomography measurement was performed by using seismic source to observe width of the EDZ. Observation area is 3m square horizontal plane along the sidewall of the 140m gallery. During excavation of the 140m gallery, seismic tomography measurement was performed repeatedly with processing of excavation of the gallery, and the change of velocity distribution of the rock around the gallery was observed. Seismic tomography investigation caught the EDZ developed around the excavated gallery.