The ABCs of ACBs - What Have We Learned, 12 Years Later Armoring Embankment Dams, Levees and Spillways with ACBs

摘要

Over the past 23 years numerous embankment dams and earth-cut spillways in the United States have been armored with Articulating Concrete Blocks (ACBs) to provide overtopping protection and to extend the life of the structures. With the current focus on evaluating and rehabilitating dams throughout the United States to pass increased design flows, the use of this construction technology has become popular. As a result, some ACB manufacturers have made significant investments in research and development of their concrete block systems to evaluate and improve their performance for use on embankment dams and earth-cut spillways, provide design data for designers, and develop more economical embankment armoring solutions. In addition to established ACB manufacturers, researchers from the USDA, Department of the Interior Bureau of Reclamation and the U.S. Army Corps of Engineers have designed, tested, and patented ACB systems and details for use on embankment dams, spillways and channels. In 2001, the primary author presented a paper titled: The ABCs of ACBs - An Assessment of Articulating Concrete Blocks for Embankment Overtopping Protection [Schweiger, 2001]. This paper provides a brief history of the use of ACBs in the United States which included a summary of findings from research and laboratory testing of various ACB systems and summarized the status of ASTM standards being developed to address the manufacture, testing, design, and installation of ACBs for armoring embankment dams and spillways. At that time, only 25 dams had been armored using ACBs for overtopping protection. Because of the infrequency of the design events, none of these dams had experienced an overtopping event. Since that time, there have been many changes in ACB armoring technology with new ACB manufacturers entering the market with new products, additional full scale physical modeling performed for a wider range of flow conditions, and new and improved design details have been developed. Several dams and spillways armored with ACBs have been overtopped and performed satisfactorily with overtopping flow depths and velocities approaching 4 feet and 30 feet per second, respectively. Over the same period, at least one known ACB overtopping application has failed. Much has been learned about what works and what does not work. The purpose of this paper is to provide an update on important developments in the use of ACBs for armoring embankment dams and spillways, and to share performance information from actual ACB dam armoring projects that have experienced overtopping flows.