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One Side Exposed to Waves
Both Sides Exposed to Waves
Preliminary Geometry
Refined Geometry
Evaluation of Construction Techniques
Selected Construction Technique
Evaluation of Materials
Redesign?
Preliminary Choice of Armor Units
Evaluation of Preliminary Design
Functional Evaluation
Economic Evaluation
Environmental/AestheticEvaluation
Modify DesignsOr Abandon Project Final Design
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
Preliminary Design Phases
1. Structure geometry2. Evaluate construction technique3. Evaluate design materials
• Crest Elevation– Prevent excessive overtopping rates
• Depends on height of runup
– Excessive overtopping causes• Lee-side choppiness
• Serious top-bank erosion (e.g. behind revetments)
• Excessive waves in navigation channels
Smooth Impermeable Slopes
Additional Factors
γγγγr - Influence of surface roughnessγγγγb - Influence of fronting bermγγγγh - Influence of shallow waterγγγγββββ - Influence of approaching wave angle
Impermeable Rock Slopes
Permeable Rock Slopes
Coefficients
Generally expressed in the form...
Typical CEM Table(one of six)
Critical AverageOvertoppingDischarges
Crest width:
• Depends on overtopping• Best evaluated with model studies• Little guidance available• Minimum is 3 armor stones wide• Consider use of crest
• Vehicles • Equipment
• Concrete Caps (Superstructures)– Strengthens the crest
– Deflects overtopping away from leeward slope
– Increases crest height
– Provides roadway access for vehicles and equipment
Failure Related to Superstructures
• Concrete Caps (Superstructures)– Requires cap & structure stability studies
– Economic evaluation of cap versus higher rock structure
Armor layer thickness:
Riprap layer thickness:
(whichever is greatest)
Bottom Elevation of Primary Cover Layer:Extend downslope to elevation below SWL equalto the design wave heightH when the structure is in aDepth > 1.5 H.
Extend to the bottom if Depth < 1.5 H.
Bottom Elevation of Primary Cover Layer:To prevent underlayer rock from being pulled through the armor layer,
D15 (cover) < 5 D85 (under)
Failure Due to Toe Berm Erosion and Scour
Toe Berm for Cover Layer Stability
Minimum Height of Toe
Minimum Width of Toe
(where W in these equationsis 1/10 the size
of armor layer stone)
W
Failure Due to Overtopping and Toe Erosion
Failure Due to Other Toe Problems
Backside Slope Failure Due to Overtopping
• Lee-side Cover Layer– Based on
• OVERTOPPING
• LEE-SIDE WAVES
• POROSITY
• HYDROSTATIC PRESSURE
• Lee-side Cover Layer– If minor overtopping present,
• Lee-side armor should be the same as seaward side
• Extending down to SWL or -0.5H (preliminary)
• Model tests recommended.
– If significant overtopping present,• Extend to bottom
One Side Exposed to Waves
Secondary Layer
• Secondary Layer• As thick or thicker than primary• Example:
• Primary: 2 stones thick• Secondary:
• n = 2.5 (between –1.5 &–2H)• n = 5 (below –2H)
•Interface slope as shown
• UNDERLAYERS
One Side Exposed to Waves
• FILTER LAYERS
• STRUCTURE HEADS•At the head and up to15m to 45m on the leeward side, the seaward side armor stone should be used.
Coastal Engineering Practice CommitteeCEM Preview
Movement of armor units• Rocking• Displacement from layer• Sliding of layer• Settlement of layer
Not armor unit breakage
Coastal Engineering Practice CommitteeCEM Preview
Parameter Stability Equation
Coastal Engineering Practice CommitteeCEM Preview
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
Coastal Engineering Practice CommitteeCEM Preview
Coastal Engineering Practice CommitteeCEM Preview
Coastal Engineering Practice CommitteeCEM Preview
Classified by:• Type of armor unit• Water depth• Superstructure• Dynamic• Crest elevation
• Non-overtopped• Low-crested• Submerged
• Based on small-scale physical models• Testing of designs is recommended• Always test unusual designs
Model Testing
Coastal Engineering Practice CommitteeCEM Preview
Coastal Engineering Practice CommitteeCEM Preview
Design Guidance for These Situations
Hudson’s Equation
Coastal Engineering Practice CommitteeCEM Preview
Coastal Engineering Practice CommitteeCEM Preview
Coastal Engineering Practice CommitteeCEM Preview
Coastal Engineering Practice CommitteeCEM Preview
Coastal Engineering Practice CommitteeCEM Preview
Coastal Engineering Practice CommitteeCEM Preview
Coastal Engineering Practice CommitteeCEM Preview
where
Coastal Engineering Practice CommitteeCEM Preview
Gradation Range:
with
Coastal Engineering Practice CommitteeCEM Preview
Design guidance for:• Sloping trunk and head• Vertical trunk and head
Toe berms…• Support main armor layer• Prevent damage by scour
Coastal Engineering Practice CommitteeCEM Preview
Coastal Engineering Practice CommitteeCEM Preview
One Side Exposed to Waves
Coastal Engineering Practice CommitteeCEM Preview
Both Sides Exposed to Waves
Coastal Engineering Practice CommitteeCEM Preview
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
Preliminary Design Phases
1. Structure geometry2. Evaluate construction
technique3. Evaluate design materials
Coastal Engineering Practice CommitteeCEM Preview
Crest width:
Armor layer thickness:
Riprap layer thickness:
(whichever is greatest)
SUMMARY: ARMORSUMMARY: ARMOR--LAYER STABILITYLAYER STABILITY
1. Hudson (1974) SPM (1984)1. Hudson (1974) SPM (1984)•• Limited applicabilityLimited applicability
-- ONLY permeable structuresONLY permeable structures-- ONLY nonONLY non--overtopping wave conditionsovertopping wave conditions
•• Factors not consideredFactors not considered-- Wave period, Wave period, TTpp-- Variable structure permeability, PVariable structure permeability, P-- Damage level, SDamage level, S-- Storm duration (number of waves), tStorm duration (number of waves), tdd
SUMMARY: ARMORSUMMARY: ARMOR--LAYER STABILITYLAYER STABILITY
2. CEM (2000)2. CEM (2000)•• No limitationsNo limitations
-- Includes wave overtopping and Includes wave overtopping and submerged submerged condtionscondtions
-- Includes Includes TTpp, P, S and t, P, S and tdd factorsfactors•• Methods easy for EXCELMethods easy for EXCEL•• Includes partial safety factors for designIncludes partial safety factors for design
Use CEM (2000) methods to estimate armorUse CEM (2000) methods to estimate armor--layer stability.layer stability.
A COURSE INCOASTAL DEFENSE SYSTEMS IITIDES, STORM SURGE and WAVESJack E. Davis, PhD
van der Meer.pdf11-coversheet.pdfA COURSE INCOASTAL DEFENSE SYSTEMS ISTRUCTURAL DESIGNBy DAVE BASCO, PhD