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SPECIALTY WORKSHOP: SITES TRAINING AND INTRODUCTION TO WINDAM ASDSO Dam Safety 2008

PART 2 – SITES EARTH SPILLWAY EVALUATION B. Earth Spillway Integrity Analysis b. Characterization of geologic materials: i & ii. History and weakness of Kh & kd. SPECIALTY WORKSHOP: SITES TRAINING AND INTRODUCTION TO WINDAM ASDSO Dam Safety 2008. OBJECTIVES.

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SPECIALTY WORKSHOP: SITES TRAINING AND INTRODUCTION TO WINDAM ASDSO Dam Safety 2008

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  1. PART 2 – SITES EARTH SPILLWAY EVALUATION B. Earth Spillway Integrity Analysisb. Characterization of geologic materials: i & ii. History and weakness of Kh & kd SPECIALTY WORKSHOP: SITES TRAINING AND INTRODUCTION TO WINDAM ASDSO Dam Safety 2008

  2. OBJECTIVES • History of Kh • Field Observations • Origin of Concepts • Kh • Kh Issues

  3. 1983 -The ESFSTG was formed 1991 - ARS & SCS established DAES Team

  4. History of Concepts • TR 71 The NRCS first used the Rock Material Field Classification (RMFC) system to classify rock performance for several engineering applications. • TR-71 Second Edition revised version of the RMFC system by John Moore. • Revised version of RFMC published in ASTM STP – 984 (Moore) • NEH Part 628 Chapter 52 Field Procedures Guide for the Headcut Erodibility INDEX • 2002 Chapter 12 Rock Material Classification System

  5. History of Concepts • TR 71 The NRCS first used the Rock Material Field Classification (RMFC) system to classify rock performance for several engineering applications. • TR-71 Second Edition revised version of the RMFC system by John Moore. • Revised version of RFMC published in ASTM STP – 984 (Moore) • NEH Part 628 Chapter 52 Field Procedures Guide for the Headcut Erodibility INDEX • 2002 Chapter 12 Rock Material Classification System

  6. History of Concepts • ASAE Transactions Vol 32, No 6 “Mechanics of an Earth Spillway Failure” (Temple). • ASAE Applied Engineering in Agriculture; Vol 8, No. 2 “Estimating Flood Damage to Vegetated Deep Soil Spillways.” (Temple) • Bulletin of AEG Vol 31 No. 2, “Headcut Advance Threshold in Earth Spillways” (Moore et. al.) • 1997 ASAE Transactions Vol. 40, No 3 “Headcut Advance for Earth Spillways” (Temple and Moore)

  7. History of Concepts • ASAE Transactions Vol 32, No 6 “Mechanics of an Earth Spillway Failure” (Temple). • ASAE Applied Engineering in Agriculture; Vol 8, No. 2 “Estimating Flood Damage to Vegetated Deep Soil Spillways.” (Temple) • Bulletin of AEG Vol 31 No. 2, “Headcut Advance Threshold in Earth Spillways” (Moore et. al.) • 1997 ASAE Transactions Vol. 40, No 3 “Headcut Advance for Earth Spillways” (Temple and Moore)

  8. HEADCUT MIGRATION dx/dt = C (A - Ao) dX/dt = rate of headcut migration, C = material-dependent advance rate coefficient, A = hydraulic attack, and Ao = material-dependent threshold.

  9. HYDRAULIC ATTACK A = (q q H

  10. MATERIAL-DEPENDENT PARAMETERS AO & C are a function of Kh = headcut erodibility index

  11. [ _ 189 Kh1/2exp(-3.23/ln(101Kh)) ]1/3 Kh> 0.01 AO = 0 Kh< 0.01 AND - 0.79 ln(Kh) + 3.04 Kh< 18.2 C = 0.75 Kh > 18.2 _

  12. Kh issues • Empirical relations based on small amount of data. • Not the only parameter important to spillway erosion. • Spillway erosion is a three phase process • Erosion is dependent on spillway slope, vegetation, material detachment erodibility, flow stress, process, etc. • Large reductions in Kh may not result in spillway breach if other factors are controlling the process. • Kh is represented in logrithmic space.

  13. Kh issues (continued) • Technology is relatively young and will continue to require additional research and change. • classification system is based on weighted parameters. Relative importance of each element is not completely understood. • The classification system includes materials from soils to massive rock but • Difficult to determine soil structure • Original development of Kh for soil did not include soil structure. Elements were commonly assumed equal to 1 with the exception of material strength (Ms)

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