Case Study of Oh-hara Dam Embankment Rehabilitated by Cement-mixed Muddy Soil for Seismic Resistant-Reinforcement

Abstract

Oh-hara dam was constructed as the center core type fill-dam for irrigation in 1953. About 55 years has passed when the dam was repaired, as reported in this paper. The safety inspection of the embankment indicated that the embankment was insufficient in the stability during earthquake, and the leaking was developed at the crest by aging.
This paper presents a case study of Oh-hara dam rehabilitated for the seismic resistant-reinforcement and leakage control of the embankment by a cement-mixed soil. The zoning for rehabilitation consisting of upstream and downstream buttress random zones and the center core zone at the crest was designed to fit in the original embankment. The muddy soil that added the soil excavated from the original embankment to the mud in reservoir at the rate of 1: 1.5 by volume was utilized for making the cement-mixed embankment soil. As the result, the excavated soil produced under construction was used up effectively as the embankment soil without the disposal at outside of dam site, and the reservoir capacity of about 30,000m³ was increased in addition to removing the mud in reservoir of about 26,000m³.