us army corps of engineers of coastal …oas.org/cdcm_train/courses/course3/chap_1b.pdf• 4000...

US Army Corpsof Engineers

CHL: Steven Hughes, PhD

Monitoring and Maintenanceof Coastal Infrastructure

Steven A. Hughes, PhD, PECoastal and Hydraulics Laboratory

US Army Engineer Research and Development CenterWaterways Experiment Station

3909 Halls Ferry RoadVicksburg, Mississippi 39180-6199

Email: [email protected]

Materials in Coastal Design(Continued)



Materials in Coastal Design

Contents

• Material Requirements• Earth and Sand• Stone• Portland Cement and Asphalt• Steel and Other Metals• Wood• Geotextiles and Plastics

Based on CEM Chapter VI-4



Portland Cement and Asphalt

Uses of Concrete in Coastal Construction

• Seawalls, Revetments, Bulkheads. Massive, cast-in-placestructures. Interlocking block armor. Poured cover layersabove water. Sheetpiles.

• Jetties and Breakwaters. Grout. Rib-caps. Filled cellularstructures in mild waves. Weir sections with prestressedsheetpiles.

• Groins. Sheetpiles or concrete panels.• Caissons. Prefab sections. Concrete caps. Other structural

features.(Continued)




Uses of Concrete in Coastal Construction

• Armor Units. High strength concrete for reinforced or

unreinforced cast armor units.

• Piles. Reinforced or prestressed piles for piers and wharfs.

• Floating Structures. Concrete pontoons. Floating

breakwaters.

• Other Applications. Land-based facilities. Outfalls.

Pipelines. Encasing wood or steel structure components.

(Concluded)




Uses of Asphalt in Coastal Construction

• Dikes. Not common in U.S. Many Dutch applications.

• Jetties and Breakwaters. Used only as binder or filler for

rubble mounds. Crest roadway.

• Revetments. Riprap binder for stronger, impermeable slope.

Asphalt slopes where wave action is minimal.

• Roadways and Slope Protection. Bituminous concrete used

for road construction and surfaces on wharfs and quays. Lining

drainage ponds and ditches.




Types of Portland Cement




Important Concrete Properties

• Strength. Based on compression. Bending resistance comes

from reinforcement. Strength increases as water content

decreases. Aggregates and entrained air also factors.

(Continued)





(Continued)

Typical Compressive Strengths of Concrete





(Continued)

Compressive Strengths for Different Water-Cement Ratios





• Durability. Weathering due to freeze/thaw cycles and

restrained expansion. Chemicals can cause cracking. Steel

corrosion problem in salt water. Cavitation and abrasion can

wear away concrete.

• Workability. Mixture's handling, transport, placement, and

finishing behavior. Different requirements for different

structures. Avoid segregation.

(Continued)




Important Concrete Properties• Consistency. Function of water content, aggregates in wet

concrete. Trade-off between strength and "flow." Judged by

"slump."

(Continued)





• Water Tightness. Improved by low air entrainment and

thorough "working." Improved with admixtures.

• Specific Weight. Varies between 140-160 lb/cu.ft. Depending

on aggregates, mixture ratios and reinforcement.

• Volume Change. Contraction causes cracks. Shrinkage

during curing increases with water content.

(Continued)




Important Concrete Properties(Concluded)

Average Unit Weight of Fresh Concrete




Important Asphalt Properties

• Wide range of bituminous concrete availablewith different characteristics

• Physical properties stem from the asphaltcement (aggregates are durable)

• Not affected by chemicals (except petroleum-based products)

(Continued)




Important Asphalt Properties

• Flexible and conforms to uneven surfaces

• Allows for differential movements

• Can be porous or impervious

• Plastic or elastic properties depending ontemperature

(Concluded)




Asphalt Blending Considerations

• Sufficient quantities of asphalt to ensure mixturedurability

• Proper type and size distribution of aggregates

• Sufficient voids in mixture to allow for slightcompaction without loss of stability andimpermeability

• Good workability of heated mixture for easyplacement




Concrete Construction Practices

• Transport. Objective to deliver to site without altering water-

cement ratio, slump, air content.

• Placement. Keep plastic and free of cold joints. Minimize

lateral movement. Avoid adding water to increase flow. No

high drops or high-velocity discharge. Don't over-vibrate.

• Curing. Prevent rapid moisture loss. Protect from freezing.

• Formwork Removal. Oil forms before placement. No form

removal until concrete can withstand combined dead and live

loads.(Continued)




Concrete Construction Practices

• Reinforcement Cover Layer. Minimum 50 mm cover over

steel with 65 mm in splash zone. Prestressed members 75 mm

and 90 mm.

• Joints and Sealants. Contraction and expansion joints allow

for volume change. Construction joints facilitate construction

sequence.

• Repairs. Fill cracks with epoxy. Grout air holes.

(Concluded)




Concrete Armor Units

• Units are vulnerable to tension breakage with no reinforcement

• Reinforcement cost is high (doubles cost of unit)

• Large units have little tension strength beyond supporting self weight.

Design for NO MOVEMENT.

• High strength concrete lowers risk of breakage

• Special fabrication precautions

• Vibrate to remove all voids

• Units should be properly cured

• Avoid rapid curing to minimize thermal cracks

• Special equipment needed for handling, transport, and placement




Environmental Effects on Concrete

• Pollutants. Sulfates and acids can damage concrete. In general,

most pollutants will not cause damage. Asphalt damaged by

petroleum-based products.

• Water Penetration. Salt water can corrode steel reinforcement and

cause spalling. Periodic wetting and drying may cause cracks.

Asphalt is generally impervious and resistant to water penetration.

• Waves and Currents. No affect on well-designed structures. High

flows at discontinuities may cause cavitation and deterioration.

(Continued)





• Ice and Temperature Change. Water freezing in cracks causes

spalling and breakage. Ice impacts and ice loading stresses can

damage. Normal temperature differentials are controlled by good

design. Asphalt can melt if exposed to fire, and become brittle if cold.

• Marine Organisms. No food value for marine critters. Barnacles

have no impact other than additional drag. Asphalt is susceptible to

damage from crustaceous organisms.

(Continued)





• Abrasion. Wind and water borne particles can wear concrete surface

over time. Asphalt resists erosion quite well.

• Seismic Activity. Earthquakes can damage concrete structures by

direct loading. Asphalt is plastic and deforms in earth movements.

• Other Effects. Concrete has good resistance to fire, is not affected

by sunlight, and is hard to vandalize (does provide ample graffiti

canvas).

(Concluded)




Contents





Steel and Other Metals

Uses in Coastal Construction

• Steel. Rolled, cast, and stainless• Concrete reinforcement• Pipe piles and H-piles• Sheetpiles• Conventional steel framing• Fendering/mooring components and specialty items• Wire for gabions, etc.• Fasteners

(Continued)




• Aluminum Alloys. Corrosion resistant• Buildings: Door and window frames, framing

materials, roofing, and siding.• Decking, catwalks, railings, supports• Fasteners

• Other Metals.• Copper: Electrical wiring, pipes• Brass: Hardware fittings, fasteners, survey

monuments• Monel and Titanium: Rare

(Concluded)




Applicable U.S. Steel Standards




Aluminum Alloy Series


• 1000 Series. 99% Al, high thermal and electrical conductivity, loweststrength, 1350 is used for wiring.

• 2000 Series. Copper is major alloying element. Less corrosionresistance.

• 3000 Series. Manganese is major alloying element. Roofing and sidingis usually 3004 aluminum.

• 4000 Series. Silicon is major alloying element. Low melting point.Used in welding and brazing wire.

• 5000 Series. Magnesium is major alloying element. Moderate to highstrength, good corrosion resistance, good for welding.

• 6000 Series. Silicon and Magnesium in equal portions. Mediumstrength, heat-treatable, good corrosion resistance. Windows, doorframes, and lamp posts of 6063 aluminum.

• 7000 Series. Zinc is major alloying element. Heat treatable with veryhigh strength.



Aluminum Alloy Series


• Aluminum alloys 5083, 5086, 5052, and 6061 arecommonly used for applications in the marineenvironment

• Alloys from the 1000, 3000, and 6000 series are alsoused, but have less corrosion resistance.

• Aluminum alloys can be used in the splash zone, butare not recommended for continuous immersion.

• Method of tempering the alloy is an importantconsideration.



General Physical Properties

• Metals in General:• Homogeneous• Consistent strength• Easily formed into shapes• Vary from rigid to flexible, ductile to brittle, soft to hard.

• Steel:• Easily joined• High tensile strength• Good ductility• Good toughness• Wide availability in stock sizes.

(Continued)




General Physical Properties(Concluded)


• Aluminum Alloys:• High corrosion resistance• Good strength-to-weight ratios• Different allow series for specific uses.

• Other Metals.• Copper: High electrical conductivity, workability, and

corrosion resistance.• Brass and Monel: High corrosion resistance. Good

strength and workability.



Tensile Stress Limits - Steel




Tensile Stress Limits - Aluminum




Tensile Stress Limits - Other Metals




General Construction Aspects

• Galvanic Reaction. Contact

between dissimilar metals

causes corrosion. More noble

metal (cathode) protected by

"sacrificial anode" such as zinc.

(Continued)


Galvanic Series in Seawater

Most active (least noble)

Least active (most noble)




• Chose metals close together on galvanic series

• Electrically insulate the metals at contact points

• Protective coating on the more active metal (anode)

• Place a more active metal in contact with coupled metals as

sacrificial anode (zinc is commonly used)

• Periodically inspect and replace sacrificial anodes to extend

component life

(Continued)


If dissimilar metals must be in contact...

Mitigating Galvanic Reactions




• Protective Treatments.

• Bar steel corrodes rapidly

• Paint or tar coating must be applied and maintained

• Concrete encasement for major support structure

• Galvanizing or chrome plating

• Beware abrasion by sand

• Construction may damage factory-finished components.

(Continued)





• Fasteners and Connections. High-strength bolts have

lessened use of rivets. Field connections should be according

to specs.

• Welding and Brazing. Variety of onsite welding methods.

Oxyacetylene for carbon and alloy steels, cast iron, copper,

nickel, aluminum, and zinc alloys. Arc welding for carbon

steel and critical connections.

(Concluded)




Environmental Effects on Metals• Abrasion. Loss of metal is minor…loss of protective coating can be

serious and lead to rapid corrosion.• Corrosion. Primary concern in coastal construction. Fresh water

polluted with acids can cause severe corrosion. Salt air will corrodeunprotected steel.

• Marine Fouling. Fouling increases corrosion rates in carbon steel,stainless steel, and aluminum. Copper and copper-nickel have bestresistance to biofouling. Metal in contact with the ground can becorroded by bacteria.

• Seismic Effects. Well-designed metal structures can withstandearthquakes. Structural steel is well suited for seismic applications.





Contents





Wood


• General Wood Uses. Seawalls, revetments, bulkheads, piers,

wharfs, sand fences, floating structures, formwork, bracing, blocking.

• Untreated Lumber. Temporary uses as formwork, bracing,

machinery supports, dunnage. Interior framework not exposed to soil

or water.

• Treated Lumber. Can have contact with soil and water. Submerged

lunber should be pressure treated with coal-tar creosote.

(Continued)




• Piles and Poles. Used for pile dolphins, guide piles, channel

markers, building foundations, piers, wharfs, trestles, groins, jetties,

powerlines.

• Beams and Stringers. Treated members used for load bearing

structures such as groins, bulkheads, pier decks, wharfs, bracing.

Untreated only used in protected areas.

• Plywood and Laminated Wood. Used as building flooring,

sheathing, gusset plates, concrete forms, signs, floating structures.

Special seawater treatment.

(Concluded)

Wood



Physical and Mechanical Properties

• Main Types.

• Hardwoods shed their broad leafs in the fall.

• Most Softwoods are evergreens with needles.

• General Properties.

• Density varies with volume of air cavities.

• Wood strength increases with density.

• Strength varies parallel and perpendicular to grain.

(Continued)

Wood




• Loading Configurations.

• Parallel to Grain. Most strength in tension and compression.

Shear resistance reduced by knots, etc.

• Perpendicular to Grain. Least strength in tension and

compression. Good shear strength.

• Temperature and Moisture.

• Wood expands and contracts, but not much.

• Wood shrinks as it dries.

• Hardwoods change more than softwoods with moisture content.

Wood

(Continued)




Wood

General Characteristics of Common Wood

(Continued)




Wood

(Concluded)

General Characteristics of Common Wood




(Continued)

Wood

• Protective Treatments.

• Treatment prevents marine borers, etc.

• Pressure treat with coal-tar creosote formaximum penetration.

• Untreated wood piles can be encased inprotective armor.

• Avoid field cutting or boring of treated lumber.



General Construction Aspects(Concluded)

Wood

• Fasteners and Connections.

• Metal connectors should be protected fromcorrosion.

• Adhesives should be water-proof.

• Restrict field-applied adhesives to secondaryjoints.



Wood

Environmental Effects on Wood• Water will penetrate and cause swelling with strength reduction.• Polluted water may help preserve wood by reducing oxygen that

supports wood-attacking marine biota.• Marine organisms are principal cause of wood destruction for

immersed timbers and piles. Proper preservatives are essential.Marine plants do not seem to harm wood, but may cause slipperysurfaces.

• Dry wood can catch fire, but large structural members can toleratesome fire damage before failing.

• Abrasion by harder objects can reduce load bearing cross section.• Wood structures absorb impact energy well.• Human activities and vandalism can wear wood structures.




Contents





Geotextiles and Plastics

Uses of Geotextiles in Coastal Construction

• Filters. A fabric layer between sand or soil andoverlying gravel/stone layer that permits waterdrainage. Replaces granular filters.

• Geotextile Bags. Large bags filled with sand arestacked and used as coastal structures (groins,seawalls, etc.)

• Miscellaneous Uses. Seperate different soil layers.Control bank erosion. Cap contaminated dredgematerial. Provide drainage. Reinforce soil banksagainst lateral movement.




Typical Uses ofGeotextile Fabric inCoastal Revetment




Advantages of Geotextiles in Coastal Construction

• Filtering characteristics are uniform• Fabrics can withstand tensile stress• Geotextile placement is more easily controlled• Underwater placement likely to be more successful

than comparable gravel filters• Inspection and quality control is quick and accurate• Local availability is not a cost consideration




Disadvantages of Geotextiles in Coastal Construction

• Difficult to repair damaged in-situ fabric, particularlyunder several layers of stone

• Some fabrics are relatively impervious to rapidhydraulic transients, leading to uplift pressures(design issue)

• Susceptible to undermining at structure toe if notproperly anchored




Other Forms of Plastic• High-strength nylon fabric.

• Flexible concrete forms• Grout-filled plastic tubes

• Impervious plastic sheets (visqueen).• Liners and covers to prevent seepage• Shield unprotected metal or timber during construction

• Highly porous plastic mesh (dune fence).• High-strength molded plastic.

• Fenders• Line and protect piles• Polyester pipe to replace steel pile• PVC pipe to 25 cm diameter• Epoxy resins



General Design Requirements

• Tensile Strength. Resist tearing by movement of

overlying materials.

• Elongation at Failure. Pore elongation results in soil

loss.

• Puncture Resistance. Survive placement of overlying

materials and movement of materials.

• Abrasion Resistance. Resistance to constant chaffing

by overlying materials.

(Continued)




General Design Requirements

• Durability. Must perform consistently over structure life• Site-Specific Factors. Freeze/thaw conditions or

exposure to chemicals.• Construction Factors. More difficult to place

underwater. Wave action may cause excessivemovement before overlayer can be placed.

(Concluded)




Geotextile Material Properties




Minimum Geotextile Fabric Requirements




Geotextile Installation Considerations


• Geotextile Placement.• Lay loosely, free of wrinkles, creases, and folds. Avoid stretched

fabric.

• For slopes exposed to waves begin at slope toe and proceedupslope with upslode panel overlapping downslope panel.

• In currents the upstream panel should overlap the downstreampanel.

• Properly terminate fabric to protect undermining.

• Horizontal underwater placement, start at structure and proceedaway from the structure.

• Overlying gravel layers must be permeable

• Placement of overlying stones begin at toe and proceed upslope.

• Avoid puncturing fabric during stone layer construction.

(Continued)





• Securing Pins.• Should be 5 mm in diameter and capable of holding 3.8 cm

diameter washer.

• Minimum pin length of 45 cm for medium to high densitysoils (longer for looser soils).

• Place at overlap midpoints.

• Pin spacing at maximum of 0.6 m for slopes steeper than 1-on-3, maximum of 1.0 m for slopes between 1:3 and 1:4, and1.5 m for milder slopes.

• Use additional pins as needed to prevent fabric slippage.

(Continued)





• Seams and Joins.• Lengths can be long, but width of sheets is limited by

practical considerations of manufacture and transport.

• Wider panels reduce number of overlaps (most probablecause of error during placement)

• Above water, overlaps should be at least 45 cm andstaggered.

• Below water, overlaps should be at least 1 m.

• Fabric seams can be glued or sewn (sewn preferred onsite).

(Continued)





• Geotextile Repairs.• During construction, repair damage by cutting out fabric and

replacing with a section giving 0.6 m overlap all around.Edges of replacement fabric should be placed beneathoriginal panel.

• Replace entire panel if tensile strength is needed to reinforceslope.

• Remove overlying stone layers to expose damagedgeotextile fabric beneath rubble slopes.

(Concluded)



ConstructionLimitations:QuarrystoneRevetment




ConstructionLimitations:BlockRevetments &SubaqueousApplications




Environmental Effects on Geotextiles and Plastics


• Chemical and Biological. Generally notbiodegradable, not affected by chemicals found incoastal waters. Alkalis and fuel products can destroysome plastics. Bacterial growth can clog fabric.

• Ultraviolet Radiation. Plastics deteriorate insunlight, but stabilizers can be added duringmanufacture. Not problem for submerged or coveredfabric.

• Fire. Will burn/melt and may release toxic fumes.

• Other Factors. Impact loads, abrasion, vandelism.



Conclusions

• Coastal projects require a large quantity ofconstruction materials

• Proper design requires an understanding materialproperties

• Material specifications are important in designdocuments

• Field engineers must be knowledgable aboutmaterials used in the project

• Inspectors must assure material quality is high andappropriate handling techniques are used duringconstruction

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