2025 Volume 35 Issue 1 Pages 67-80
Seismic wave velocities in the embankment of Naramata Dam in Gunma prefecture, Japan, operated by the Japan Water Agency and the vibration characteristics of the embankment were examined. The results revealed that (1) the estimated S-wave velocities were respectively 350-360 m/s and 540-570 m/s in the upper and the lower sections of the core zone, and (2) those in rock zones were 560-600 m/s in both the upstream and downstream side, and a polarity anisotropy of the S-wave velocities was seen. (3) The P-wave velocities were 520 m/s in the upper section and 1,950 m/s in the lower section of the core zone and (4) 1,800 m/s in the upstream side and 1,100 m/s in the downstream side of the rock zones, and this difference is attributed to the saturation of soils due to the reservoir water. (5) The natural frequency of the embankment evaluated by FE-BE analysis based on the abovementioned soil properties was identical with that obtained from observed spectrum ratios.
