repair and rehabilitaytion of coastal structures

7/24/2019 Repair and Rehabilitaytion of Coastal Structures

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US Army Corps

of Engineers

CHL: Steven Hughes, PhD

Monitoring and Maintenance of

Coastal Infrastructure

Steven A. Hughes, Ph, PE

Coastal and Hydraulics Laboratory

US Army Engineer Research and Develoment Center

!ater"ays E#eriment Station

$%&% Halls 'erry Road(ic)sburg, *ississii $%+&-.+%%

Email! Steven.A.Hughes"erdc.usace.army.mil

#epair and #eha$ilitation of

Coastal Structures


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of Engineers


Contents

/ 0eneral Asects o1 Reair and Rehabilitation

/ Rubble-*ound Structures

/ 2ther 3yes o1 Coastal Structures

%ased on! CE* Chater (4- 5Author: Steven A6 Hughes7

#epair and #eha$ilitation

of Coastal Structures


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efinitions

#epair! 'i#ing ortions o1 a structure that have beendamaged by "aves, "inds, currents, surges, imacts,

or seimic activity.

#eha$ilitation! Renovation o1 deteriorated structurecomonents to original condition or upgrading thestructure to "ithstand greater design loads6

&eneral Aspects of



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'hen is #epair (eeded)

&eneral Aspects of


/A1ter damaging storms or other damagingevents

/ !hen eriodic condition insections indicaterogressive deterioration

/ 41 er1ormance monitoring indicates the ro8ect isnot 1unctioning as lanned

/ !hen there is chronic damage 1romunderestimating design loads

/ !hen structure 1unction is modi1ied


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Should Pro*ect $e #epaired)

&eneral Aspects of


/ !hat 1unctions are served by the ro8ect/Are other commerce activities a11ected9

/ Has ris) o1 in8ury increased9

/ Ho" critical is the ro8ect relative to otherro8ects in need o1 reair

/ Economic Considerations

/ Possibility o1 imminent 1ailure or collase

epends Upon...


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ifferences +rom (e esign

esign Enviroment Considerations!

&eneral Aspects of


/ 4n general, no di11erence in actual designarameters 5"aves, "ater levels, etc67

/ *ay have better estimates o1 designarameters

/ Regulatoryenvironmental restrictionsrobably changed

/ Can dra" on ast er1ormance andmonitoring data


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Components for Preparing esign

-6 Revie" original design criteria

6 Determine the cause o1 the roblems

/6 4nvestigate the resent structure relative to the as-built lans

06 Devise a solution to the roblem

16 Design a reair that 1i#es roblem "ithout e#tensive modi1ications

&eneral esign Steps

It helps if you have: 2riginal lans and secs/As-built lans/ Cororate memory

&eneral Aspects of#epair and #eha$ilitation


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Contents



/ 2ther 3yes o1 Coastal Structures





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#u$$le2Mound Structures



/ Relatively 1le#ible "ith tolerance to slightmovement o1 armor

/ Damage is usually/Armor unit brea)age

/ Dislocation o1 armor

/ Removal o1 a section o1 armor


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3ptions for #u$$le2Mound Structures

#eplace 3riginal Structure

Slope and Crest #epair

Chin)ing, resur1acing/Addition o1 dissimilar armor/ Layer reconstruction/ Crest raising/ ;urial

4oe and +oundation #epair

/ 3oe reconstruction/ Scour aron/Addition o1 a berm

Core #epair or 5oid Sealing/ Precast concrete bloc)s/ 'ilter cloth/ 0rout




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#epair Considerations!

Availability o1 construction materials

/ E


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Construction

E6uipmentfor #u$$le2

MoundStructure#epairs




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#epair of Armor and Underlayers

&eneral Categories of Armor 7ayer #epair/ Sot relacement o1 bro)en or dislodged

units

/ 2verlaying e#isting armor layers

/ Relacing armor layers/ Rebuilding the structure

esign guidance is sparse8mostly common sense rules2of2thum$


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Spot #eplacement of Units

/ Damage consists o1 individual dislacedarmor units

/ >o large sections o1 armor dislaced/ >o evidence o1 general sloe 1ailure/ Percentage o1 dislaced units is ?@ or less

'hen to Use Spot #eplacement #epair


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/ Relace dislodged armor units "ith units o1similar tye and si=e

/ Reuse dislaced units I+ sound and notbro)en into smaller ieces

/ Sulement "ith ne" units

#epair Method


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/ Reair underlayer i1 necessary/Achieve good interloc)ing o1 armor units

/ 41 undamaged armor interloc)ing is good, relace

dislodged units "ith good contact "ith neighbors

/ 41 undamaged matri# is loose, rehandle armor as

necessary so reair section has interloc)ing

#oc9 Armor #epair 4echni6ue


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0ood interloc)ing is essential 1or stability

/ Remove and relace undamaged armor layer 1rom

the damage location all the "ay u the sloe

/ Reair section should resemble a (B

/Assure good interloc)ing "ith undisturbed ortions

Concrete Armor #epair 4echni6ue


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/ Least e#ensive/ Shorter time on site/ Less ne" material costs

/ Less rehandling o1 e#isting armor

Advantages

Caveat

4mortant to establish damage caused by design

event and not by a lesser storm event


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3verlaying amaged Armor 7ayers

'hen to Use Armor 3verlays

/Armor layer damage is "ide-sread

/ Large sections are dislaced or slumed

/ Damage "as caused by the design storm ora more severe condition 5but not al"ays7

21ten damaged structure has lo"er crest and

milder sloes than originally built


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/ Single-layer stone overlays/ Uses less material

/ >o design guidance, must test in hysical model

/ 3"o-layer stone overlays/ Use ne" construction guidance

/ *odel test large ro8ects

/ 2verlays using dissimilar armor units/ Usually concrete armor units over stone

/ Design guidance available

/ *odel test large ro8ects

#epair Methods


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Sta$ilityCoefficients

for issimilar

Armor 7ayer3verlays


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Armor 7ayer 3verlay Concerns

/Armor inter1ace "ith e#isting underlying armor

/ E#tra e11ort to achieve interloc)ing bet"een armor layers/ Under"ater ortion is very di11icultuneven sloe

/ Leeside crest armor units/ ey into e#isting structure 5overtoing stability7

/ 2verlay toe

/ *ust be secured and rotected 5may need ne" toe berm7/ Dislodged armor stones may litter the bottom

/ Construction methods/ ;egin at toe and "or) usloe

/ *ay need to build u uneven underlayer


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/ Less e#ensive than relacing armor layer/ Can be used to raise crest and reduce sloe/ Larger armor stones can be used

Advantages

isadvantages/ Large


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#eplacing Armor 7ayers

'hen to #eplace Armor 7ayers

/ 2riginal armor layer is inade23 caused by armor instability


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/ Remove e#isting armor layer on a section/ *ay need to ad8ust or relace e#isting 1irst underlayer

/ 4ncrease underlayer si=e to accommodate larger

relacement armor

/Assure roer thic)ness and comaction

/ ;uild 1rom the toe and roceed usloe/ Plan construction se


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/ Provides a more stable structure "ith less 1uturemaintenance cost/ Provides intended 5or enhanced7 1unctionality/ Use ne" construction design guidance

Advantages

isadvantages/ (ery e#ensive/ Long construction times "hich may imact activities

at the ro8ect site

/ Site stoc)iling o1 construction materials


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#e$uilding the Structure

'hen to #e$uild

/ Structure sustains catastrohic damage/ Structure integrity has been lost

/ Reair ree" 1unctionality re


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#epair Method

/ #e$uild at the same location/ *ay need to bury or comletely remove e#isting structure/ Preare relic structure to serve as base 1or ne" structure

F Remove material 5ma8or e#ense7

F Preare ne" toe

F Lay do"n bedding material

/ Probably "ill result in larger cross section/ Reuse materials or cost "ill be greater than ne" construction

/ #e$uild ad*acent to old a$andoned structure/ Re


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/ *ore robust structure/ Less long-term maintenance costs/ 4mroved 5or ne"7 1unctionality

Advantages

isadvantages/ (ery e#ensive to remove e#isiting structure/ (ery e#ensive to build ne" structure/ Disrution to ro8ect activites



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/ Damage occurs "hen/ Concrete sections are dislodged by "ave action/ Underlying suort stones are lost

/ Di11erential settlement

/ Concrete sections may remain intact or theymay brea) because o1 loading, movement orinade


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/ Correct minor dislacements "ith hydraulic8ac)s or cranes

/ Remove ca sections and relace missingunderlying armor unitsG relace ca section

/ Relace bro)en sections "ith ne" elements/ Remove damaged cast-in-lace sections and

cast ne" sections

#epairing Caps and Cron 'alls



#epair Methods


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/ 4oes and %erms

/ 'or minor damage add ne" material o1 same si=eas needed

/ 'or ma8or damage redesign berm

/ Scour holes and $edding/ 'ill and rotect scour areas according to guidance

/ 5oid sealing/ Reduces "ave and sand transmission

/ Cors guidance available

3ther Aspects of #epair




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Contents



/2ther 3yes o1 Coastal Structures





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3ther 4ypes of Coastal Structures

/ >ot very tolerant to movement or settlement/ Damage is usually

/ Di11erential settlement

/ Dislocation o1 sections

/ ;rea)age o1 sections or comonents

/ Concrete salling

/ Comonent deterioration

Caissons


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Caissons

/ islocation! Li1t and reseat sections 1or smallstructures, remove and relace large sections

/ Settlement!Add to to o1 caisson to achieve crestelevation

/ 7ocali:ed damage! Patch, reair and relaceaccording to circumstances




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4ypes of Concrete #epair

/ Concrete #eplacement

/ Relace de1ective concrete "ith machine-mi#ed concrete o1roer tye

/ ;est 1or large reairs "here damage is beyond rein1orcement

/ ry Pac9/ Sti11 mi#ture rammed into lace in thin layers

/ >arro" slots and cavities

/ Shotcrete/ ;onds "ell "ith ne" or old concrete

/ 0ood 1or shallo" reairs and vertical or overhead sur1aces




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Categories of #epair

/ Class -! eterioration %arrier Systems

/Acts as a barrier to revent or delay 1urther deterioration/ Comleted as maintenance item

/ Reair is non-load bearing

/ Class ! Structural #einforcing

/ Strengthens e#isting, "ea)ened load-bear members

/ Part o1 rehabilitation

/ Class /! Structural #eplacement

/ Partial or comlete relacement o1 structural member




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/ Class -! eterioration

%arrier Systems

/ Class /! Structural

#eplacement

/ Class ! Structural

#einforcing




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#epair of

Pilings




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Conclusions



/ 4mortant to )no" "hen reair or rehabilitation is needed

/ Understand di11erences bet"een RR and ne" design

/ ;ase decisions on structure 1unctionality andconse

repair and rehabilitaytion of coastal structures

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