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Research & development

Open Stone Asphalt Spillways

Research and Development

Open Stone Asphalt Spillways

When reservoir water levels exceed the designed top water level for a dam, water will flow over/in a designed structure and discharged into the watercourse downstream.  One example of this type of structure is a spillweir at the top water level with a spillway on the downstream face of the dam.

The spillway requires erosion protection which is robust enough to withstand the high hydraulic loads but which is also aesthetically acceptable as for the majority of the time the spillway will be dry.  Open Stone Asphalt (OSA) is a suitable material but there was a lack of information on the design of OSA spillways.

With several flood alleviation schemes planned in Germany Karlsruhe University was commissioned to undertake studies on OSA spillways and Hesselberg Hydro was asked to give advice on the mix design, installation routines and material knowledge.

After laboratory studies and tests on scale models the first scheme in Germany was installed in 2003.  Since then several schemes have been installed and more are planned.  In the UK the first project designed with the information learned from the research is due to start on site in 2008.

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