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REQUIREMENTS AND RECOMMENDATIONSFOR NONDISRUPTIVE ROAD CROSSINGS

2002 Edition / Version 1.0

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SECTION 1:

REQUIREMENTS FOR NONDISRUPTIVE ROAD CROSSINGS

1.1 SUBMITTALS REQUIRED FOR PERMIT TO CONDUCT NDRC 6

1.2 MONITORING SYSTEM 6

1.3 UNACCEPTABLE GROUND SURFACE MOVEMENT 7

1.4 REPAIR AND REINSTATEMENT 7

1.5 PROTECTION OF ADJACENT AREAS AND WORKS 7

SECTION 2:

RECOMMENDATIONS FOR NONDISRUPTIVE ROAD CROSSINGS

2.1 PURPOSE AND SCOPE 10

2.2 PRELIMINARY NDRC PLANNING 10

2.3 GEOTECHNICAL INVESTIGATION 10

2.3.1 RPOSE 10

2.3.1.1 ROUTE SELECTION 10

2.3.1.2 NDRC METHOD SELECTION AND OPTIMIZATION 11

2.3.1.3 DETERMINATION OF DESIGN PARAMETERS 11

2.3.2 SCOPE OF THE GEOTECHNICAL INVESTIGATION 11

2.4 DESIGN 11

2.4.1 ENGINEERING ANALYSIS 11

2.4.1.1 GENERAL ANALYSIS OF THE NDRC DRIVE 11

2.4.1.2 GROUND SURFACE MOVEMENT 12

2.4.1.3 SHORING FOR ENTRY AND EXIT PITS 13

2.4.1.4 DEWATERING 13

2.4.1.5 GROUND IMPROVEMENT 13

2.4.1.6 ALTERNATIVES TO NDRC TECHNIQUES 14

2.4.2 GENERAL RECOMMENDATIONS FOR DESIGN OF NDRCS 14

2.4.2.1 DEPTH 14

2.4.2.2 LOCATION OF ENTRY AND EXIT PITS 14

2.5 CONSTRUCTION SUPERVISION AND MONITORING 14

CONTENTS

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REQUIREMENTS FORNONDISRUPTIVE

ROAD CROSSINGS

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Requirements and Recommendations for Nondistruptive Road Crossings2002 Edition / Municipality of Abu Dhabi City

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2 Upon completion o NDRC construction.

3 At a subsequent time ater completion o NDRC construction as directed by the De-

partment.

Benchmarks or measurement o elevation shall be located a minimum o 50 meters outside

o the monitoring area.

All survey work shall be done using equipment capable o an accuracy o 0.1 millimeter.

1.3 UNACCEPTABLE GROUND SURFACE MOVEMENT

Unacceptable ground surace movement (settlement or heave) s hall be dened

as movement greater than 6.0 millimeters vertically anywhere in a rectangular areacovering the entire width o the roadway along the drive and to boundaries extending

outwards rom the centerline o the NDRC drive. The distance o these boundaries rom

the centerline o the drive shall be as ollows:

ForanNDRCwithadiameter1.0meterorless,theboundariesshallbelocatedone

meter on each side o the drive centerline.

ForanNDRCwithadiametergreaterthan1.0meter,theboundariesshallbelocated

at a distance equal to the drive diameter on each side o the drive centerline.

Any ground surace movement exceeding the above limits that are detected during or

ater NDRC construction shall be immediately reported to the Department and proposed

remedial measures and/or intended actions shall be stated.

Measurements or ground surace movement shall be taken relative to the nished level o

the roadway at the time o measurement.

Ground surace movement limits in the specied area shall remain in eect or 10 years rom

dateofcompletionoftheNDRC,incompliancewithArticle16oftheGeneralConditionsof

Contract in the Field o Contracts o Civil Works.

1.4 REPAIR AND REINSTATEMENT

I ground movement as measured on the roadway surace exceeds the Departments stated

limits(Section1.3,above)orifdamageisapparentinadjacentareas,thecontractorshall

repair and

reinstatetheroadwayand/oradjacentareastotheiroriginalline,level,andcondition.The

expense or the repair and reinstatement shall be borne by the party responsible or the

project.RepairandreinstatementshallbedoneinaccordancewiththeRoadDepartments

StandardSpecicationsforRoadandBridgeConstructionandissubjecttothe

Departments approval.

1.5 PROTECTION OF ADJACENT AREAS AND WORKS

Uponcompletionofconstruction,curbs,sidewalks,orothersurfaceareasadjacenttothe

roadway shall not show any visible sign o disturbance or stress.

Any immediate or delayed damage occurring to Department property that is an indirect

result o utilities damage inficted as a result o the NDRC installation shall be the

responsibility o the contractor. Damage caused to other services or utilities shall be dealt

with separately with the concerned agency.

REQUIREMENTS FOR NONDISRUPTIVEROAD CROSSINGS

The ollowing subsections describe the Abu Dhabi Municipality Road Departments

requirements or construction o nondisruptive road crossings (NDRC).

Theserequirementsdonotcovertherequire-mentsofotheragencieswithjurisdictionfor

worksadjacenttooralreadyexistingbeneaththeroadway.Contractorsareresponsiblefor

procuringanyotherrequiredpermitsorapprovalsfromagencieswithjurisdictionoversuch

surace or subsurace works.

1.1 SUBMITTALS REQUIRED FOR PERMIT TO CONDUCT NDRC

PermissionoftheRoadDepartment(hereinafter,theDepartment)isrequiredforany

NDRCworkcarriedoutbelowpropertyunderthejurisdictionoftheDepartment.The

ollowing items shall be submitted to the Department when applying or a permit: JusticationforconductinganNDRCasop-posedtoanopencutorusingexisting

ducts.

AbriefdescriptionoftheNDRCmethodandequipmenttobeused.

ThenameofthecontractorandNDRCsub-contractorconductingtheworks.

LettersofapprovaloftheNDRCdesign,methodstatement,andsubcontractorsfrom

the consultant and the concerned agency (client) commissioning the NDRC work.

AbriefstatementonthesoilconditionsinthelocationoftheNDRC.

AgeneralplanthatclearlyshowstherouteandlocationoftheproposedNDRC.

Clearplan,prole,andsectiondrawingsoftheproposeddriveshowingthedetails

(suchasinternalandexternaldiameter,wallthickness,couplingsystem,etc.)of

thecasing(orsleeve),pipeline(carrierpipe),andintendedutilityinstallationand

their respective depths below the road surace. The drawings shall also show the

microtunnel(bore)andoverbreakdetails,aswellastheconstructiondetailsofentry

and exit pits and their planned location in relation to the road.

Sketchandscheduleofgroundsurfacemovementmonitoringsystemandbaseline

readingsformonitoringpointscollectedduringinitialsurvey(seenextsection),as

well as predicted ground movement (settlement and/or heave) based on scientic

calculations.

BankguaranteeandassociatedDepartmentalforms.

1.2 MONITORING SYSTEM

Forpurposesofmonitoringforgroundsurfacemovementontheroadway,thecontractor

shall install fush-head pins (35.0 millimeters to 50.0 millimeters in length) in the road

pavement. These pins shall be the monitoring points. The pins shall be installed in a grid

pattern with approximately 2.0-meter centers.

The grid o monitoring points shall cover the entire width o the roadway along the drive and

shall extend outwards in each direction rom the centerline o the drive to a distance o the

drive centerline depth below the road surace.

The contractor shall conduct surveys o all monitoring points and provide the Department

with drawings and precise survey inormation on each point three times:

1 Prior to commencement o NDRC construction (see Section 2.5 or Departmental

recommendation on the establishment o monitoring point baseline inormation).

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2.3.1.2 NDRC METHOD SELECTION AND OPTIMIZATION

The soil investigation analysis should be used as the basis or the selection o the optimum

NDRCmethodandrelevanttunnelingmachinery(pipejacking,microtunneling,jetdrilling,

directionaldrilling,augerboring,etc.),aswellasfordeningtheoptimumoperational

variables(RPM,axialfeedrate,torque,ushandlubricantrate

andspecications,facepressure,etc.)forthechosentechnique.

2.3.1.3 DETERMINATION OF DESIGN PARAMETERS

Theinvestigationshouldresultinproperlyobtained,reliablesoilparameters,whichare

necessaryforadequatedesignofthedrives,shoring,anddewateringdetails.Analysisand

design(calculationsforjackingforces,stressanalysisonthepipeline,groundsurfacesettle-

mentandheaveanalysis,etc.)shouldbebasedonsuchparameters.

2.3.2 SCOPE OF THE GEOTECHNICAL INVESTIGATION

The inormation collected in the geotechnical investigation may include:

Typicalsoilprolesandgroundwaterlevels.

Indexandphaseparameters,suchas:

- Soil classication.

- Phaseparameters,suchasunitweight(),relativedensity(Dr),moisturecontent

(),saturation(S),voidratio(e),porosity(n),andanyotherparametersthatmaybe

useul.

- Shearstrengthparameters,suchascohesion(c),frictionangle(),andunconned

compressive strength (qu).

- Elasticconstantssuchastheelasticmodulus(E),PoissonRatio(),andsub-grade

reaction coecient (K).

- Soilcompressibilityandcollapsecoefcients,suchasvolumecompressibility

(mv,av,M)constantsparameters;compressionindices(dc,dr,etc.),andpre-

compression pressures (pp).

- Permeability (k) and erodability parameters.

- Any other relevant parameters.

2.4 DESIGN

Duringthisstage,adetailedengineeringanalysisshouldbecarriedoutapplyingtheresults

o the geotechnical investigation to the design o t he systems proposed in the preliminary

planning stage.

2.4.1 ENGINEERING ANALYSIS

Engineering analysis includes general geotech-nical analyses o the various aspects and

components o the proposed NDRC system as well as a check on the eects o the drive on

theexistingroadwayandadjacentareas.Thisincludes,butisnotlimitedto,thefollowing:

2.4.1.1 GENERAL ANALYSIS OF THE NDRC DRIVE

An NDRC system should be developed using available actual soil data and surrounding

RECOMMENDATIONS FOR NONDISRUPTIVEROAD CROSSINGS

2.1 PURPOSE AND SCOPE

Thissectionprovidesgeneralrecommendationsforplanning,design,andexecutionof

NDRCworksbelowpropertyunderthejurisdictionoftheDepartment.

NDRCworksconductedbelowAbuDhabiroad-waysunderthejurisdictionofthe

Departmentbyandatthebehestofotherentitiesaresubjecttotheperformance

requirementsoftheDepartment.Itistheresponsibilityofthecontractor,consultant,client

(concernedagency),andanyotherpartiesinvolvedintheconstructionofanNDRCunder

anAbuDhabiroadwaytoensurethatroadpavement,pertinentservices,andadjacent

areas such as sidewalks are not damaged and that any eects are within the acceptable

tolerances stated in the Departments NDRC requirements (Section 1 o this document).

Thesearerecommendationsofgoodpracticesfortheplanning,design,andexecutionof

successul NDRC works. Parties conducting an NDRC are expected to have a sucient

level o knowledge and expertise to carry out the construction successully.

2.2 PRELIMINARY NDRC PLANNING

Basedoninitialsitereconnaissanceandavailablesoilaswellasutilityinformation,adesk

study should be conducted to plan the method and route most appropriate or the purpose

in the given soil conditions. The desk study should accommodate the existing constraints

andallsurroundingconditions.Atthisstage,preliminaryanalysisisusefulincheckingthe

suitability o the proposed NDRC method.

The presence o surace and underground works in the area o the proposed NDRC should

be thoroughly investigated at this stage. Structural and pavement elements must be

considered,aswellasutilities.Conrmationofthepresenceor

absence o underground utilities is best achieved by excavate to locate. As-built drawings

alone may not be sucient or this purpose.

IfutilitiesarelocatedintheimmediatevicinityoftheNDRCwork,contractorsshould

coordinate with the concerned department or agency. Approval by the utility provider may

berequired,andtheprovidermaydemandspecicmeasuresbetakentoprotectitsassets.

2.3 GEOTECHNICAL INVESTIGATION

IfinsufcientgeotechnicalinformationisavailablefortheareawhereanNDRCisproposed,

then a thorough geotechnical investi-gation should be conducted.

2.3.1 PURPOSE

Anumberofobjectivescanbeachievedbyageotechnicalinvestigation:

2.3.1.1 ROUTE SELECTION

Theinvestigationshouldprovidesufcientgroundsfordeningthelineandleveloftheroute,

astheoptimumZ/Dratio(Z=depthtocrownofdrive,D=diameterofdrive)dependsonthe

typeofsoilstrataencounteredandtheNDRCmethodused.TheZ/Dratio,localground

conditions,andtheNDRCmethodhaveadirectrelationshiptothemagnitudeofsurface

deormation (settlement or heave) and breadth o the area aected.

The soil investigation should target specic routing considerations such as to avoid driving

throughweak/strongsoilboundaries,weatheringinterfaces,andgroundwatersurfaces.

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methods may be needed to suciently analyze potential ground movement.

Sincetolerancesagainstgroundsurfacemove-mentsaresmall,theDepartment

recommendsthatveryconservativeassumptionsandmethodsbeusedandthattotal,not

fractional,movementsbedetermined.

Modesofanalysisshouldincludeallrelevantprinciples,whichinclude,butarenotlimitedto:

Elastic,elastoplastic,andviscoplasticdeformationalbehavior.

Immediate,short-term,andlong-termmovements.

Consolidation,collapse,andswell.

Volumetriccompressionandexpansion.

Volumeloss,soilpiping,internalerosion,andhydrocompaction.

Fractionalandtotalgroundmovements.

2.4.1.3 SHORING FOR ENTRY AND EXIT PITS

Proper shoring analysis and design should be conducted to meet the allowable shear

forces,bendingmoments,deections,andminimumpenetration(socketing)requirements

ofthewallsystem.Likewise,properanalysisanddesignoftheproposedsupportsystems

(anchors,bracing,strutting,waling,etc.)shouldbecarriedoutinaccordancewith

internationally acceptable practice.

Wheredesignagainstfullorpartialexternalhydraulicpressuresisassumed,watertight

shor-ing construction should be specied to satisy this condition. This construction should

preclude soil erosion (soil piping behind shoring) and ground settlement around the pits.

Hydraulic pressures behind shoring should never be allowed to exceed values considered in

the design calculations.

Analyticalorempiricalapproachesmaybeused,providedthevalidityandapplicabilityofthe

selectedapproachesarejustied.

2.4.1.4 DEWATERING

Dewateringsystems,includinganappropriatelteraroundriserpipes,shouldbecarefully

considered and designed properly. The lter design should ensure against the possibility o

any internal soil erosion that might cause ground settlement and collapse along t he drive or

around shoring boundaries. Filters can be either conventional soil lters or geotextile lters.

The Department preers and recommends the use o geotextile lters.

2.4.1.5 GROUND IMPROVEMENT

In cases where conventional NDRC methods seem to be unavorable or a particular

appli-cationorgivengroundconditions,orincaseswhereextremesensitivity(interms

oftolerance)oftheadjacentexistingworksdonotfavoranyoftheavailablemethods

alone,groundimprovement,suchassoilgrouting,maybenecessary.Thegoalofground

improvement is to enhance local conditions along the proposed route. Cementitious or

chemicalgroutsystemsappliedbefore,during,orafterconstructionarepossible

alternatives,dependingonexistinggroundconditions.


constraints.Thesystemshouldincluderecom-mendedroute(lineandlevel),boringsize,

NDRCmethod,pipelinedetails,equipment,andoperationalvariables,allofwhich,in

combina-tion,willachievetherequiredtolerances.Theproposedsystemshouldthenbe

analyzed or:

Jacking/pullingforces.

Lubricantcharacteristics.

Facestabil ity.

Thrustreactionelements.

Structuraldesignofpipeandjoints.

Groundsurfacemovement(settlementandheave).

2.4.1.2 GROUND SURFACE MOVEMENT

As ground surace movement is the chie risk and problem aced in attempting a successul

NDRC,itspreventionisdiscussedinmoredetailinthefollowingsubsections.

a. Ground Surface Movements Caused by NDRC Method and Pipeline

The combination o NDRC drive methods and pipeline details are key to preventing

excessivesurfacemovement,whichmayberelatedto:

Diameteranddepthofdrive.

Boringmethodandpractice.

Stiffnessofpipeandjointsystemandstruc-turalintegrity.

Jointalignment.

Maximumjacking/pullingforces.

Lubricationandushdetails.

Pipe/soilinteraction.

Overbreakanditsmanagement.

Facesupportdetails.

Groundwatercontroldetails.

b. Ground Surface Movement Due to Unfavorable Ground Conditions

Regardlessofdrivemethodordetails,sur-roundingsoilmaybesusceptibleto

excessive movements when disturbed by the drive (bore). The ollowing conditions can

infuence ground movements:

Residualorswellstressesleadingtoradial-elasticortime-dependentmovements.

Weaksoilsorshearfailureoftheface.

Loosecompressiblesoilsaroundorabovethedriveleadingtodensicationandhence

ground movement upon disturbance.

Internalerosionofloose,noncohesivesoilduetouncontrolledgroundwater

movements.

c. Movement Analysis Methods

Usingoneoracombinationofnumericalmod-elingmethods,theoreticalandempirical

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operational variables against the completed driving distance in a properly recorded time

frame.Thisrecordcanbeusedasatoolandreferenceforinspectionandcontrol,andisa

permanent record or troubleshooting and interpretation o a drives behavior.

ThroughoutNDRCconstruction,existingworks(roads,nearbystructures,andutilities)

should be requently monitored under the supervision o qualied sta to detect any ground

surace movement.

BeforeConstruction

The Department recommends that several surveys be conducted o the monitoring

points prior to commencement o NDRC construction to establish a baseline level or

each point.

DuringConstruction

The Department recommends that moni-toring points are surveyed or ground surace

movementtwiceeachworkshift,andmorefrequentlyifanymovementisdetected.

AfterCompletionofConstruction

The Department recommends that moni-toring points be surveyed or ground surace

movementonceperdayforaminimumofoneweek,followedbyprogressively

decreasing requency or several months.

The Departments requirements or a monitoring system during NDRC work are

included in Section 1 o this document.


2.4.1.6 ALTERNATIVES TO NDRC TECHNIQUES

Some situations and congurations are not conducive to or prevent the construction o

NDRCs.Forexample,itmaynotbefeasibletoconstructalarge-diameterNDRCwhere

structures or other impediments would require entry and exit pits to be located very near

pavement boundaries.

Where engineering analysis and design suggest that tolerances can not be practically

metwithconventionalNDRCtechniquesandwheregroundimprovementisnotfeasible,

alternatives to NDRC systems should be considered. The goal o these systems is to allow

placement o the required pipelines while minimizing trac disruption. Alternative systems

available include:

Placingreinforcedconcreteslabs(preferablyprecast)belowthepavementlayerson

pregrouted soil abutments and excavating under the slabs. Trac disruption in this

case would be o limited duration and stabilization by anchoring and bolting would be

possible during excavation.

Open-trenchpipe-layingorprecastductinstallationfollowedbyquickbackllingusing

low-strength concrete or an approved fuidized quick-setting cementitious backll

material. Disruption to trac would be very minimal as the duration o the backlling

activity would be short.

Severalothersystemsasdescribedinengineeringandconstructionmethodslitera-

ture.

2.4.2 GENERAL RECOMMENDATIONS FOR DESIGN OF NDRCS

2.4.2.1 DEPTH

ForNDRCswithadiameterof1.0meterorless,theDepartmentrecommendsaminimum

depthof3.0meters,measuredfromtheroadsurfacetothecrownofthedrive.ForNDRCs

withadiameterofgreaterthan1.0meter,theDepartmentrecommendsaminimumdepth

o three times the NDRCs diameter.

Inotherwords,whereD=diameterofdriveandZ=depthtocrownofdrive,the

recommended criteria are:

IfD1.0meter,Z3.0meters. IfD>1.0meter,Z3D.

2.4.2.2 LOCATION OF ENTRY AND EXIT PITS

The Department recommends that entry and exit pits or construction o NDRCs be located

a minimum o 5.0 meters rom the edges o the paved roadway.

2.5 CONSTRUCTION SUPERVISION AND MONITORING

Qualied supervisory sta should be present in the eld during the execution o NDRC works

to ensure that the approved design and method are being ollowed.

Onceconstructionhasbegun,automatedormanualrecordingofalloperationalvariables,

progress,drivebehavior,etc.,shouldbecarriedouttoensurecompliancewiththeintended

set o operational variables. The record produced should orm a continuous log o all

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