Rock deformation and support load in shaft sinking in Horonobe URL Project

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

Observational construction is essential in underground excavation since it is difficult to estimate rock mass properties based on geological investigation from the ground surface. In the construction, the amount of support elements at the next stage is redesigned by measuring rock mass deformation and support stress caused by excavation. JAEA has been constructing an underground research laboratory in Horonobe. Based on the observational construction, ventilation and access shafts have been excavated 250 m deep and 140 m deep from the ground surface, respectively. The authors investigated the relationship between the initial deformation rate and stress of concrete lining. The initial deformation rate is related to the ratio of the elastic modulus of rock mass to the initial stress and one of indices of rock mass properties. The relationship is helpful to determine whether the amount of designed support elements should be changed at the earlier stage of excavation.