Proceedings-DFI/EFFC 11th International Conference on Piling and Deep Foundations, 2014, Stockholm, Sweden, (DFI)
A Brand New Barrier Wall Installed at Wolf Creek Dam
Maurizio Siepi and Carlo Crippa, Trevi S.p.A, Italy; Fabio Santillan, TREVIICOS, USA; Lyndon Bedford, Soletanche Bachy UK, United Kingdom
Wolf Creek dam, on the Cumberland River in Kentucky, US, operated and maintained by the Nashville District of the USACE, is the Corps' largest reservoir east of the Mississippi river. The 1748 m (5,736 ft) long Wolf Creek dam combines earthfill and concrete gravity sections. Construction began in 1941 and was completed in 1950. The dam showed signs of instability in the 1960ís, and in the late 70ís an in-depth project of rehabilitation was undertaken, using both grouting and secant piles. The works saved the dam, but in the late 90ís further signs of distress worried the Nashville district of USACE which, after a study conducted on the water seepage, concluded that construction of a new concrete barrier cut-off wall was needed. In 2009, the $341.4 USD million contract was awarded to TREVIICOS-SOLETANCHE JV. The new wall, located upstream of the concrete monoliths, has a minimum thickness of 60 cm (24 in.), and runs the length of the embankment, into the right abutment, for about 4,200 feet. The founding depth reaches 84 m (275 feet), well below the zone of solutioning. With a total surface approaching 92,903 sq.m (1,000,000 sq.ft), the Wolf Creek barrier wall is unlike any other project in the world. The construction of the cut-off wall followed a complicated but logical sequence of several operations, involving a variety of technologies: grouting, hydromill, directional drilling, and secant piles with reverse circulation. The intensive rock grouting program was aimed to minimize the risk of slurry loss and extend the positive cut-off further deep. Subsequently, an Encasement Concrete wall was installed with hydromill, toeing into the rock, to protect the embankment during the following phases. Smart holes were then drilled into the Encasement wall down to the final depth. Eventually, the holes were used to install the secant piles by employing the reverse circulation piling method. An extensive verification campaign has confirmed the superior quality of the cutoff wall consisting of 1200 secant piles, exceeding by far USACEís requirements. The main project was substantially completed in early 2013. A small portion of secant piles wall will be installed downstream of the dam, to close the switchyard, finishing the project in the early months of 2014.
|article #1959; publication #100 (IC-2014)|