Introducing NRCS Design Guidance for Articulated Concrete Block Armored Spillways

摘要

The USDA Natural Resources Conservation Service (NRCS) has planned, designed, constructed, and rehabilitated dams for over 80 years. These dams are an important part of United States infrastructure. The proper design and maintenance of these structures is critical for their effective and safe operation. The NRCS does not allow water to pass over a dam without a designated spillway. An auxiliary spillway conveys runoff flows that are in excess of what the principal spillway can convey. The spillway must function with minimal risk of a dam breach. NRCS typically constructs auxiliary spillways as open channels excavated into natural materials. The lining of the auxiliary spillway channel can range from grass to structural concrete. Articulated Concrete Blocks (ACBs) have recently been used as an effective erosion resistant spillway lining. An ACB system is a matrix of interconnected concrete block units with specific hydraulic characteristics. ACB armored spillways have an elements of strength and durability that a vegetated spillway does not have, but often with important cost savings compared to a traditional structural spillway. The proper design and installation of all components of an ACB armored spillway system are critical to its successful performance. Recently the NRCS has developed guidance for the use of ACBs in spillways. This guidance was developed in cooperation with industry and academia. The document, titled "ACB Armored Spillways" will be part of the NRCS National Engineering Handbook and is currently under final review. The document includes sections: 1. Basic concepts of ACB Armored Spillway Materials 2. Basic Concepts of ACB Armored Spillway Design 3. Hydraulic Design of Armored Spillways Using ACB 4. Design Considerations for Armored Spillway Design using ACBs 5. Construction Issues for ACB Armored Spillways 6. Approval of ACB Designs 7. ACB Installation Details 8. ACB Maintenance This presentation will overview the NRCS guidance and provides information regarding its development as well as how it can be obtained by practitioners. This paper will be of interest to dam planners and engineers.