Ohdo Dam Landslide
Conditions following the completion of mitigation works
- Niyodo-Son Tazaki, Takaoka-Gun, Kochi Prefecture, (33_ 32'N; 133_ 05'E).SIZE OF SLIDE:
- Size of Slide
- Length: 170 m; Width: 150 m.
- A relocated local roadway was closed due to 0.5 to 2 m high cracks caused by the landslide. The slide occurred on April 19, 1982.
- Geology, Mechanism of Failure and Type of Movement
- The area above the relocated local roadway is underlain by chert interbedded with slate. The slopes below the road are underlain by siliceous schalstein interbedded with dolomite. The siliceous schalstein was fractured by tectonic activity, and further weakened by infiltration of water. It has been suggested that the rock slide occurred following the rapid failure of the lower slopes due to saturation during the early stages of the infiltration process. The rapid failure of the lower slopes acted as a triggering mechanism for the rock slide, which occurred along fault planes situated along the upper portion of the slope.
- Mitigation Measures
- Since the failure of the lower slopes was close to the triggering mechanism of the main slide, the mitigation measures on the lower slopes is very important. Anchor works and grating crib works were implemented on the lower slopes as well as anchor works on the upper slopes.
Conditions immediately following the slide
Cross section of the Ohdo Dam Landslide