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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: iv. Characterizing the k d factor Soils. SPECIALTY WORKSHOP: SITES TRAINING AND INTRODUCTION TO WINDAM ASDSO Dam Safety 2008. Resources.

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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: iv. Characterizing the kd factor Soils SPECIALTY WORKSHOP: SITES TRAINING AND INTRODUCTION TO WINDAM ASDSO Dam Safety 2008

  2. Resources • Chapter 51, Part 628, NRCS National Engineering Handbook – Earth Spillway Erosion Model • ASTM D5852, Erodibility Determination of Soil in the Field or in the Laboratory by the Jet Index Method

  3. Representative Particle Diameter Figure 51-1 Critical Shear Stress, t, lb/ft2 10-3 10-2 10-1 1 10 Particle Diameter, inches

  4. Objectives • State the common range of the Kd parameter for soils • Using example soil data, assign a value to the Kd parameter accurately • Identify tests used to characterize soils for estimating the Kd parameter

  5. DETACHMENT RATE EQUATION • Units of kd are gd ( )3.10 gw gd gd = dry density of material gw = dry density of material c%= clay percentage

  6. Summary of Factors to compute Kd • Dry Density, gd • Percent finer than 2m (% clay) • Practical range is from 0.01 to 1 • Number is inversely related to resistance to erosion – low value is high resistance, high value is low resistance • Note units are in ft/hr of downward erosion per unit applied stress of lb/ft2

  7. Kd versus Kh values based on flume studies - ARS

  8. Summary of Kd Values • Flume data indicates Kd values could be as high as 10 for very low Kh values (near 0.01) • Equation employing percent clay and dry density predicts lower bound value for Kd of less than 5

  9. Jet Erosion Test ASTM D5852 t

  10. Jet Erosion Test – Greg Hanson t

  11. Not Applicable for Soils with Structure Particle sizes > 7 cm

  12. Jet Erosion Test in NY Spillway

  13. Summary • The Kd parameter is inversely proportional to the Kh parameter • The Kd parameter is a function of the percent clay and the dry density of soils • An alternative is to specifiy the particle diameter of the soils or bedrock

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