First-arrival traveltime tomography for monitoring the excavation damaged zone in the Horonobe Underground Research Laboratory

Ozaki, Yusuke  

In this study, a series of data repeatedly acquired by first arrival traveltime tomography for seven years was analyzed to investigate the time-lapse behavior of excavation damaged zone (EDZ) at 350 m stage in the Horonobe Underground Research Laboratory. The data was highly affected by the shotcrete on the drift wall, and a priori information on the structure of shotcrete was incorporated into the inversion process to alleviate the effect. In addition, time-lapse inversion was applied to trace the change in P-wave velocity in time. Our inversion results indicated that time dependent change of EDZ was not recognized under open-drift condition during the period in the site.