Rehabilitation of the Kölnbrein Dam/Austria-Paper

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The 200 m-high Kölnbrein Dam in Austria is the country’s largest concrete dam. After its first major reservoir filling in 1978, horizontal cracks developed in the central dam blocks, causing seepage of up to 200 litres per second and sharply increased foundation water pressure. Earlier repairs—including cement and resin injections, a temporary freezing curtain, and upstream sealing measures—did not provide a lasting solution.<br /><br />A rehabilitation plan developed by Professor Lombardi added a downstream support arch to reduce loads on the cracked dam. The structure, built with about 460,000 m³ of concrete, was connected to the original dam through adjustable neoprene bearings designed to transfer the support forces while accommodating movement between the structures.<br /><br />Grouting was a central part of the rehabilitation. Extensive drilling and monitoring informed targeted treatment of the bedrock and concrete. Cement grout was used to consolidate and seal rock, while specially developed RODUR epoxy resins filled cracks in the dam concrete. Grouting pressures and quantities were controlled using the GIN method to limit the risk of creating further cracks. Approximately 130,000 m of injection, testing, and monitoring boreholes were completed, and about 200 tonnes of resin were injected.<br /><br />The rehabilitation was completed in 1994, restoring unrestricted power-plant operation and allowing the reservoir to reach its maximum level again. Monitoring showed that the structures generally behaved as expected. After roughly two decades of operation, minor increases in seepage were traced to new small cracks, rather than deterioration of the original resin. Targeted regrouting in 2011–2012 used about five tonnes of resin and restored tightness.

Keywords

Kölnbrein Dam

Austria

concrete dam

reservoir seepage

horizontal cracks

downstream support arch

grouting rehabilitation

epoxy resin injection

GIN method

structural monitoring