Rubble-Mound Stability

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1 Design of Marine Structures Rubble-Mound Stability Steven A. Hughes. Ph.D., P.E. Coastal and Hydraulics Laboratory US Army Engineer Research and Development Center David R. Basco. Ph.D., P.E. Coastal Engineering Center Old Dominion University

2 Design of Marine Structures Contents Overview of Armor Layer Stability Rubble-Mound Trunk and Head Stability Riprap and Toe Stability Cross-Section Design Example Problems Based on: CEM Chapter VI-5-3 (Author: Hans F. Burcharth) CEM Chapter VI-7 (Author: David R. Basco)

3 Armor Layer Stability Hydraulic Instability Movement of armor units Rocking Displacement from layer Sliding of layer Settlement of layer Not armor unit breakage

4 Armor Layer Stability Stability Parameter Parameter Stability Equation

5 Armor Layer Stability Stability Variables Sea State Variables Wave height Wave length Wave steepness Wave angle Wave Asymmetry Spectrum shape Water depth Water density Structure Variables Armor layer slope Freeboard Armor density Armor gradation Armor weight Armor shape Packing density Layer thickness Porosity of layers

6 Armor Layer Stability Damage Parameters

7 Armor Layer Stability Damage Parameters

8 Armor Layer Stability Stability Formula Classification Classified by: Type of armor unit Water depth Superstructure Dynamic Crest elevation Non-overtopped Low-crested Submerged Model Testing Based on small-scale physical models Testing of designs is recommended Always test unusual designs

9 Armor Layer Stability Armor Layer Permeability

10 Design of Marine Structures Contents Overview of Armor Layer Stability Rubble-Mound Trunk and Head Stability Riprap and Toe Stability Cross-Section Design Example Problems Based on: CEM Chapter VI-5-3 (Author: Hans F. Burcharth) CEM Chapter VI-7 (Author: David R. Basco)

11 Rubble-Mound Stability Structure Trunk Stability Design Guidance for These Situations

12 Stability Formula Table Hudson s Equation

13 Rubble-Mound Stability Hudson s Stability Equation

14 Rubble-Mound Stability Hudson s Stability Equation

15 Rubble-Mound Stability Van der Meer s Stability Equation

16 Rubble-Mound Stability Structure Head Stability

17 Rubble-Mound Stability Structure Head Stability where

18 Design of Marine Structures Contents Overview of Armor Layer Stability Rubble-Mound Trunk and Head Stability Riprap and Toe Stability Cross-Section Design Example Problems Based on: CEM Chapter VI-5-3 (Author: Hans F. Burcharth) CEM Chapter VI-7 (Author: David R. Basco)

19 Riprap and Toe Stability Riprap Stability with Gradation Range:

20 Riprap and Toe Stability Toe Stability Toe berms Support main armor layer Prevent damage by scour Design guidance for: Sloping trunk and head Vertical trunk and head

21 Riprap and Toe Stability Toe Stability

22 Design of Marine Structures Contents Overview of Armor Layer Stability Rubble-Mound Trunk and Head Stability Riprap and Toe Stability Cross-Section Design Example Problems Based on: CEM Chapter VI-5-3 (Author: Hans F. Burcharth) CEM Chapter VI-7 (Author: David R. Basco)

23 Cross-Section Design One Side Exposed to Waves

24 Cross-Section Design Both Sides Exposed to Waves

25 Cross-Section Design Phases and Aspects of Design Preliminary Design Phases 1. Structure geometry 2. Evaluate construction technique 3. Evaluate design materials Geometric Design Aspects Crest elevation and width Concrete cap Armor layer thickness Primary layer bottom elevation Toe berm Structure head Lee-side armor Underlayers Bedding/filter layer Scour protection

26 Cross-Section Design Cross-Section Geometry Crest width: Armor layer thickness: Riprap layer thickness: (whichever is greatest) CHL: Steven Hughes, PhD

27 Design of Marine Structures Contents Overview of Armor Layer Stability Rubble-Mound Trunk and Head Stability Riprap and Toe Stability Cross-Section Design Example Problems Based on: CEM Chapter VI-5-3 (Author: Hans F. Burcharth) CEM Chapter VI-7 (Author: David R. Basco)