Impact of earthquakes occuring around the Horonobe Underground Research Center to the excavation damaged zone around the shaft

Niunoya, Sumio*; Hata, Koji*; Aoyagi, Kazuhei  ; Matsui, Hiroya 

A multi-optical measurement probe consisting of an optical fiber AE sensor, a pore pressure sensor, and a thermometer was installed at a depth from 350 to 370 m of the East access shaft. Using this measurement system, we continuously monitored the EDZ around the shaft and changes in pore water pressure. In this report, we summarized the measured AE and pore pressure data during the maintenance period after the completion of excavation to a depth of 350 m, and analyze the waveform data when earthquake occurred. We also investigated whether the measurement system can capture the effect of seismic motion to the EDZ. As a result, the AE count was slightly increased and pore pressure was slightly changed owing to the seismic motion, however, there is little impact to the EDZ.