Study on mechanisms of strain variation at great depths

Japan Atomic Energy Agency (JAEA) installed the intelligent type strain meters, at G.L-500 m depth in pilot boreholes drilled from the 200 m level in the Ventilation and Main shafts of the Mizunami Underground Research Laboratory (MIU). Strain variations due to several events including the excavation itself were monitored and analyzed. Monitoring results indicate that the intelligent type strain meter is able to measure very small fluctuations and detect rock deformation from blasting with 300 m vertical separation from the measurement section. The strain meter can detect conditions in the rock mass such as differences in deformability. (author)