Trends and Innovations in RCC Dam Design and Construction

Although roller-compacted concrete (RCC) has been used for construction of dams worldwide for nearly 20 years, new techniques, materials, and construction procedures are still being developed. Further, better understanding of RCC behavior is allowing the planning, design, and construction of RCC dams of unprecedented height. The topics discussed in this paper are from the authors' international and domestic experience on over 10 RCC dam projects, including Olivenhain Dam, a 306-foot high RCC dam currently under construction in San Diego County, California. Key topics that will be addressed in this paper include: 1. Grout-Enriched RCC: Grout-enriched RCC has been used extensively in China for upstream and downstream facing of RCC dams and for RCC placement against formwork. This technology is currently under investigation in the United States and is part of placing trials currently underway at the Olivenhain Dam Project. Potential uses and drawbacks of this technique will be presented in this paper; 2. Placement Techniques: It is known that RCC lift joints represent the weakest part of any RCC dam. Recently, variations in RCC placement methods have been developed to dramatically improve lift joint quality, including the sloping lift and monolithic-block methods of construction. Advantages and disadvantages of these techniques will be discussed; 3. Geomembrane Liner Facing Systems: Geomembrane liners represent a new and controversial material for upstream facing of RCC dams. The benefits of a properly designed system extend well beyond providing enhanced seepage control and are known to include reduced pore/uplift pressures in the dam, decreased tensile stresses, and reduced potential for cracking. This paper will explore the advantages and disadvantages of geomernbrane liner systems for RCC dams; 4. RCC Appearance: The downstream slopes of many early RCC dams were unfaced RCC that resulted in an unattractive appearance, particularly as volunteer vegetation found its way onto the slopes. While this is primarily an aesthetics issue and/or owner preference, numerous options have been developed to enhance the long-term appearance of RCC dams. Several available options for improving appearance will be discussed in this paper; 5. RCC Handling and Workability: Handling and workability of RCC has been enhanced by improvements in mix design approach and delivery systems used for construction. Although these approaches are not universally accepted, the profession appears to be moving in the same direction on these issues. Industry trends in mix workability and handling will be documented in this paper. 12 pp., 4 references.