Wolf Creek Dam: Comprehensive Structural Repair prevents Dam Failure
Built in the 1940s, Wolf Creek Dam in Kentucky, USA, not only generates electricity, it also protects the entire region from floods. When the 1,748m long and 79m high dam was built as a combination of a concrete structure and an earth-fill embankment structure, the geotechnical knowledge that would have been necessary for a detailed analysis of the surrounding subsoil was not yet available. Consequently, the original cutoff trench designed for the dam foundation was too shallow. In addition, water leakage containing carbonic acid partially dissolved the limestone underneath the earth-fill embankment which resulted in cavities that were up to 12m high.
In the 1960s, seepage at the dam reservoir and two large sinkholes indicated imminent dam failure, which was initially prevented by filling the bedrock with approx. 221,720m³ of pressurized grout and by building a concrete diaphragm wall. Since the cutoff wall that was built at the time was too shallow and not wide enough to intercept the decisive cavities, in 2005, the U.S. Army Corps of Engineers once again detected uncontrollable seepage that resulted in a high risk of dam failure.
In order to prevent a catastrophe, a comprehensive structural repair program was begun in March 2006. To stabilize the dam, a new, approx. 1,160m long and 84m deep concrete diaphragm wall consisting of overlapping secant piles and rectangular panels that reach through the earth-fill embankment into loadbearing soil was built. The diaphragm wall consists of 1,197 overlapping Ø 1.27m concrete piles that were used in combination with 3.2m long and 0.8m wide panels.
Initially, grout curtains were installed upstream and downstream of the dam in order to consolidate the foundation and prevent slurry loss. Afterwards, a Protective Concrete Encasement Wall (PCEW) consisting of concrete panels was built through which the guide holes for the larger secant piles boreholes were bored into the bedrock.
The piles were installed using five Wirth Drill Rigs supplied by DSI Underground Systems USA. The bottom hole assembly of the drills is fitted with an inclinometer and has a roller rock bit face that was fitted with a 0.6m long stinger. On March 6th, 2013, the last pile was installed – a full nine months faster than originally planned.
Thanks to these innovative and comprehensive structural repair measures, residents below the dam can now relax, and tourists can return to the popular recreation area at Lake Cumberland without having to worry. The structural repair of Wolf Creek Dam was distinguished with the Outstanding Project Award by the Deep Foundations Institute in 2013.