Location: Hydraulic Engineering Research2011 Annual Report
1a. Objectives (from AD-416)
Improve methods of predicting earthen embankment erosion and failure, and develop generalized hydraulic guidelines and tools for roller compacted concrete spillways used to protect earthen structures from erosion and increase discharge capacity. Improving methods of predicting earthen embankment erosion and failure will include sub-objectives of quantification and erosion measurement of embankment materials, quantification of protective capabilities of vegetation, development of algorithms and computational models that can be used by the profession to predict earthen embankment erosion and failure causing downstream flooding. The development of generalized hydraulic guidelines and tools for roller compacted concrete spillways will include sub-objectives of development of preliminary guidelines for dimensioning converging sidewalls as well as understanding air entrainment, flow bulking and energy dissipation leading to generalized equations for dimensioning stepped spillways, downstream basins and rip-rap protection that will be used by the engineering profession to design spillways.
1b. Approach (from AD-416)
Small-scale erosion tests and large-scale physical models will be used to develop knowledge of erosion resistance of embankment materials and to develop key relationships related to earthen embankment erosion. Small-scale and large-scale physical models will also be used for water control studies. Data and relationships from physical models and case studies from the literature will be used in the development of predictive and design tools for embankment erosion and spillway design. This will include determination of allowable overtopping and erosion processes associated with overtopping and internal erosion. Other ARS, government, university, international scientists and consultants will collaborate with the USDA-ARS-HERU in carrying out these objectives. The results from this research will be incorporated into evaluation tools, software, design criteria, and management practices that will allow the continued service and increased benefit of the nation's agricultural flood control infrastructure.
3. Progress Report
The WinDAM (Windows Dam Analysis Modules) development continued with WinDAM B and WinDAM C. WinDAM B is a process-based breach erosion prediction model to be used by the profession for predicting erosion and embankment failure during a flood overtopping event. Testing and modification of a beta test version of WinDAM B continued to be carried out by ARS, Kansas State University, and NRCS scientists and engineers. WinDAM B was CCE certified by NRCS. Work also continued on the development of the next phased enhancement of WinDAM, WinDAM C. This work has involved incorporating algorithms to predict the erosion and potential embankment failure during an internal erosion event. This is a two-step process of testing the algorithms in a research computational tool SIMBA (SIMplified Breach Analysis) and developing the interface and computational modules within WinDAM to enhance the program's evaluation capabilities. Research is also being conducted: 1) in cooperation with the University of Mississippi National Center for Physical Acoustics on using physical acoustics methods for mapping embankment conditions and relating this to soil material characteristics that identify erosion prone zones within the embankment, and 2) in cooperation with Oklahoma State University on testing of a more convenient testing apparatus for measuring soil erodibility. Roller compacted concrete (RCC) stepped spillway research continued on the development of relationships for air entrainment inception point, flow depth, air concentration, and energy dissipation. The air entrainment inception point is valuable for determining other design parameters including flow depth, energy dissipation, and air concentrations for RCC stepped spillways. Air entrainment inception point relationships were optimized for stepped spillways having a broad-crested weir using data collected from a 3(H):1(V) stepped spillway physical model. The relationships were further validated from data available from literature. Data collection of velocities, flow depths, and air concentrations from a 3(H):1(V) stepped spillway model was completed. Analyses of these data are substantially completed to further enhance relationships developed for flow depth, energy dissipation, and air concentrations from a 4(H):1(V) stepped spillway model. Limited data from literature will provide independent validation for these relationships.
1. Engineering guidance for roller compacted concrete (RCC) stepped spillways. A common deficiency in aging embankment dams is inadequate spillway capacity. Researchers at the Hydraulic Engineering Research Unit (HERU), Stillwater, OK, are developing design criteria for RCC stepped spillways for overtopping protection and to increase spillway capacity for the rehabilitation of aging embankment dams. Relationships were developed for flow depth, energy dissipation, and air concentrations for 0.25 ft/ft sloped RCC stepped spillways. Data was also collected and analyzed for velocity, air concentration, and flow depth data from a 0.33-ft/ft sloped stepped spillway physical model. This data is being used to complement the previously developed relationships for the 0.25-ft/ft slope stepped spillway in order to develop a generalized equation. These relationships will provide quantifiable design guidance for engineers to use in designing RCC stepped spillways.
2. WinDAM B certification. A Common Computing Environment (CCE) certified version of the computer engineering application tool WinDAM B was developed as a cooperative effort between the USDA-ARS-Hydraulic Engineering Research Laboratory, Natural Resources Conservation Service, and Kansas State University. Prior to CCE certification the program was tested and evaluated using case histories, and synthetic data sets. The purpose of WINDAM B is to predict overtopping performance earthen embankments including allowable overtopping, breach erosion, and failure. This computer tool will be important in evaluating existing structures, with potential for determining hazard classification, emergency action plans, and reducing costs associated with rehabilitation.Benik, R.D., Cooper, C., Crowder, J., Harrington, B., Haynes, M., Hunt, S.L., Johnson, A., Kingery, R., McClenanthan, J., Pridal, D., Schaaf, D., Schlenker, S., Todaro, S., Vargas, J., Visser, K. 2010. Outlet works energy dissipators - best practices for design, construction, problem identification and evaluation, inspection, maintenance, renovation, and repair. FEMA Technical Manual P-679. CDROM