| Dahuofang Reservoir is a key project in Hunhe mainstream, build in 1950's. The reservoir serves mainly for flood control, irrigation and urban water-supply, and power generation and fish farming as well. Its total storage capacity is 2.187 billion cubic meters. The reservoir dam is an earth dam with a clay core wall, built earliest in our country. Experienced from the severe flood in Hunhe river in 1995, the original design requirement has been not met through hydrologic rechecking. Therefore this project becomes unsafe, and rebuilding for its safety is needed.For this purpose, a study on the rebuilding for safety of the large reservoir, Dahuofang is conducted in this work. Considering the three key problems associated with the safety rebuilding of large reservoirs: raising dam, enlarging discharge capacity and coordination between the flood-control project and its shielding area, and their appropriate treatment, making tech-economic comparison between different rebuilding alternatives, a relatively optimal alternative has been chosen based on the consideration about flood-control performance, construction condition and economy. The study shows that for reservoir safety rebuilding, a combination of raising dam by a certain height and enlarging flood discharge capacity to a certain degree is advantageous so that both the difficulty from over-raising dam can be alleviated, and the adverse effect of over-enlarging discharge capacity on the downstream area can be reduced.Furthermore, a detail design analyses are made for the rebuilding structures based on the local conditions including the project existing state, topography and geology. Through a large amount of computation and discrimination, the rebuilding installations are determined finally. Among them, in particular, an innovative kind of baffle block for flow deflection and energy dissipation is designed on the spillway chute, which is superior to some ordinary energy dissipaters in energy dissipation efficiency and flow guiding.
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