ABSTRACT
ABSTRACT: Many embankment dams that retain coal combustion by-products, such as fly ash, disposed from coal-fired power plants are constructed in stages. The dam is raised to provide additional capacity when the storage capacity of the original stage is reached. The Cardinal Fly Ash Retention Dam is located in eastern Ohio, USA. The original dam consisted of a 54 m (180 ft) high arched earth embankment with a zoned cross section. To increase the disposal capacity of the impoundment, the dam was raised 15m (50ft) in 1998 utilizing a composite structure consisting of a Roller Compacted Concrete (RCC) upstream shell, a clay core, a granular drainage blanket, and an earthen downstream shell. Economic analyses of various options to raise the dam lead to the unique utilization of an RCC fill with bottom ash from the plant as the aggregate for the mix in the project that also provided a beneficial long-term disposal of the bottom ash at a considerable saving. A construction method that combines the advantages of RCC and of earth fill building techniques proved to be effective and economical. The RCC characteristics for this project were evaluated on the basis of strength and durability. The lightweight RCC aggregate minimized the loading and deformation experienced by the new construction and existing structure. Cracks RCC zone were observed and monitored during and after construction. The potential effects of the cracks to the dam were evaluated. A summary of the design and construction of the dam raising is presented herein including a review of design alternatives, RCC mix design and placement, joint preparation, stability analyses, test results, and other significant QA/QC requirements.
