Thesis Analysis of Riprap Design Methods Using Predictive

Thesis Analysis Of Riprap Design Methods Using Predictive Equations For Maximum And Average Velocities At The Tips Of Transverse In-Stream Structures Submitted by Thomas Richard Parker Department of Civil and Environmental Engineering In partial fulfillment of the requirements For the Degree of Master of Science Colorado State University Fort Collins, Colorado Spring 2014 Master’s Committee: Advisor: Christopher Thornton Steven Abt John Williams Abstract Analysis Of Riprap Design Methods Using Predictive Equations For Maximum And Average Velocities At The Tips Of Transverse In-Stream Structures Transverse in-stream structures are used to enhance navigation, improve flood control, and reduce stream bank erosion. These structures are defined as elongated obstructions having one end along the bank of a channel and the other projecting into the channel center and o↵er protection of erodible banks by deflecting flow from the bank to the channel center. Redirection of the flow moves erosive forces away from the bank, which enhances bank stability. The design, e↵ectiveness, and performance of transverse in-stream structures have not been well documented, but recent e↵orts have begun to study the flow fields and profiles around and over transverse in-stream structures. It is essential for channel flow characteristics to be quantified and correlated to geometric structure parameters in order for proposed in-stream structure designs to perform e↵ectively. Areas adjacent to the tips of in-stream transverse structures are particularly susceptible to strong approach flows, and an increase in shear stress can cause instability in the in-stream structure. As a result, the tips of the structures are a major focus in design and must be protected. Riprap size is a significant component of the design and stability of transverse in-stream structures, and guidance is needed to select the appropriate size such that the structure remains stable throughout its design life. The U.S. Bureau of Reclamation contracted the Engineering Research Center at Colorado State University to construct an undistorted 1:12 Froude scale, fixed bed, physical model of ii two channel bend geometries that are characteristic of a reach of the Rio Grande River south of the Cochiti Dam in central New Mexico. A series of factors including the construction of the Cochiti Dam and control levees has caused the historically braided river to meander and become more sinuous. Bank erosion threatens farmlands, irrigation systems, levee function, aquatic habitat, and riparian vegetation. The purpose of the model was to determine the e↵ectiveness of in-stream structures in di↵using the magnitude of forces related to bank erosion. Multiple configurations of transverse in-stream structures with varying x, y, and z parameters were installed in the model, and velocity and shear stress data were collected. A series of twenty-two di↵erent configurations of transverse in-stream structures were tested. An analysis of the average and maximum velocities at the tips of the transverse in-stream structures was performed. Utilizing a channel bend approach velocity, average and maximum velocity ratios were calculated using physical model data. A set of dimensionless parameters consisting of influential structure design parameters was organized and arranged for regression analysis. Predictive equations were developed that describe the ratios of maximum and average velocity at the tips of the in-stream structures to bend-averaged velocities. The predictive equations for maximum and average velocity ratios function as a first approximation of in-stream structure riprap design for configurations that are within the range of tested data. Velocity data were used to assess the suitability of current riprap sizing techniques for transverse in-stream structures. Bank revetment design methodologies were found to be dependable methods for in-stream structure riprap design. Methodologies developed by the United States Army Corps (US- ACE) and the United States Bureau of Reclamation (USBR) were recommended for the sizing of riprap for in-stream structures. Velocity adjustment procedures were created for iii use in the USACE and USBR methods. The velocity adjustment procedures include a velocity factor for the determination of a riprap sizing design velocity. The riprap sizing design velocity produces a conservative riprap size for bank revetment, but an appropriate riprap size for in-stream transverse structures. Two velocity factors are provided: one for natural channels and the one for uniform, trapezoidal channels. Limitations and recommendations of the proposed tip velocity ratios and riprap sizing techniques are provided. iv Acknowledgements First, I would like to thank my parents and brother for their continual and unyielding support with everything I do. Next, I would like to thank Dr. Abt for providing me guidance throughout my graduate study and in my thesis research and writing. I would like to thank the rest of my committee members (Dr. Christopher Thornton and Dr. John Williams) for their guidance and feedback during the completion of my thesis. The research for the thesis could not have been done without the tremendous help and support of my Ph.D. mentors: Michael Scurlock and Natalie Youngblood. The Engineering Research Center sta↵was essential in making this all possible including: Patrick Noonan, Janice Barman, Ryan Zilly, Molly Sullivan, Shane Ritchie, Ryne Pearce, and Tyler Sobieck. Lastly, I would like to thank all of my friends and colleagues for their advice and support over the last few years. In particular, Ami Cobb has been one of the most inspirational and helpful people I have ever had the honor of working with. My graduate school studies and research could not have been completed without her continuous support and encouragement. This thesis is typset in LATEX using a document class designed by Leif Anderson. v Table of Contents Abstract.............................................................................. ii Acknowledgements.................................................................... v List of Tables......................................................................... ix List of Figures........................................................................ xii Chapter 1. Introduction............................................................. 1 1.1. General Background . 1 1.2. Project Background. 2 1.3. Research Objectives. 4 Chapter 2. Literature Review........................................................ 5 2.1. Rock Riprap Sizing . 5 2.2. Description of Riprap Sizing Methods . 6 2.3. Types of In-Stream Structures . 35 Chapter 3. Physical Model Description. 43 3.1. Introduction . 43 3.2. Model Geometry and Flow Conditions........................................ 43 3.3. Model Construction, Components and Startup................................ 46 3.4. Instrumentation and Measurements . 50 Chapter 4. Data Collection . 56 4.1. Baseline Data Collection . 56 4.2. In-Stream Structure Test Program . 56 vi Chapter 5. Data Analysis............................................................ 74 5.1. Terms for Analysis............................................................ 74 5.2. Maximum and Average Velocity Ratios (MVR & AVR) ....................... 76 5.3. Regression Analysis........................................................... 79 5.4. MVRtip & AV Rtip Results . 81 Chapter 6. Bernalillo Priority Site Case Study . 91 6.1. Introduction . 91 6.2. Bernalillo Priority Site Background . 91 6.3. HEC-RAS R Model........................................................... 94 6.4. USBR Velocity Data and Observed MVRtip’s................................. 96 6.5. Design Velocity Calculation from MVRtip’s . 100 6.6. Summary . 101 Chapter 7. Analysis of Riprap Sizing Relationships...................................103 7.1. Introduction . 103 7.2. Median Riprap Size Results . 103 7.3. Comparison of Methods . 110 7.4. Discussion of Results. 112 7.5. Average Velocity Adjustment Procedures for the USACE EM-1601 (1991) and USBR EM-25 (1984) Methods.................................................114 7.6. Example Procedures for In-stream Structure Riprap Design . 117 Chapter 8. Conclusion and Recommendations........................................123 8.1. Overview . 123 8.2. Conclusion. 124 vii 8.3. Recommendations for Further Research . 125 Bibliography..........................................................................128 Appendix A. Velocity and Weir Data for Regression Analyses........................ 134 Appendix B. Regression Analyses Results............................................152 Appendix C. Velocities for Riprap Design Analysis...................................160 Appendix D. Median Riprap Results for Agency Methodologies...................... 167 viii List of Tables 2.1 Agency, publication title, and abbreviated title of various rock riprap design procedures....................................................................... 19 2.2 Guide for selecting stability factors . 21 2.3 Guidelines for selection of Shields parameter and safety factor. 25 3.1 Similitude Scaling Used for the Physical Model (1:12 Froude Scale)............... 44 3.2 Geometric characteristics of Type 1 and 3 bends in the field. 44 3.3 Geometric characteristics of Type 1 and 3 bends in the model . 44 4.1 In-stream Structure Design Program . 59 4.2 Velocity Results from Data Collection. 67 5.1 Material Properties . 75 5.2 Channel Properties . 75 5.3 Flow Properties.................................................................

Load more