Estimation of convergence curves through shaft excavation in Horonobe underground research laboratory

Tsusaka, Kimikazu; Yamazaki, Masanao; Hatsuyama, Yoshihiro*; Yamamoto, Takuya*

Japan Atomic Energy Agency has constructed an underground research laboratory in Horonobe to establish the reliable engineering technologies related to geological disposal. At the end of March 2008, the ventilation and access shafts reached 161 m and 110 m in depth, respectively. During the shaft sinking, measurements of convergence and stress of support members are carried out in order to feed the results to the selection of the appropriate magnitude of support at deeper levels. In this paper, the authors clarified the depth distribution of the strength of rock and frequency of fracture on shaft wall and the relationship between the initial deformation rate and deformation ratio based on the convergence measurement.