andrew harris - countdown to eurocode 7 preparing

7/24/2019 Andrew Harris - Countdown to Eurocode 7 Preparing

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Countdown to Eurocode 7: preparingCountdown to Eurocode 7: preparingfor March 2010for March 2010

Andrew HarrisAndrew Harris

(Geomantix Ltd,(Geomantix Ltd,

Kingston University)Kingston University)


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Outline of presentationOutline of presentation

General rules of Eurocode 7 for SlopesGeneral rules of Eurocode 7 for Slopes

Implications of EC7 for slopesImplications of EC7 for slopes

Stability of circular slip surfacesStability of circular slip surfaces

Current developments in EC7 and NCCICurrent developments in EC7 and NCCI

documentsdocuments

Adapting to EC7 and use of softwareAdapting to EC7 and use of software

Summary of key pointsSummary of key points


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General rules ofGeneral rules of EurocodeEurocode 77

for Slopesfor Slopes


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Contents of EN 1997Contents of EN 1997--1 Sections 11 and 121 Sections 11 and 12

Section 11 Overall stabilitySection 11 Overall stability

Section 12 EmbankmentsSection 12 Embankments

x.1x.1 General (2/2 paragraphs)General (2/2 paragraphs)

x.2x.2 Limit states (2/2)Limit states (2/2)

x.3x.3 Actions and design situations (6/8)Actions and design situations (6/8)x.4x.4 Design and construction considerationsDesign and construction considerations(11/13)(11/13)

x.5x.5 Ultimate limit state design (26/7)Ultimate limit state design (26/7)

x.6x.6 Serviceability limit state design (3/4)Serviceability limit state design (3/4)

11.711.7 Monitoring (2)/Monitoring (2)/12.7 Supervision and12.7 Supervision andMonitoring (5)Monitoring (5)


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Contents of EN 1997Contents of EN 1997--1 Sections 11 and 121 Sections 11 and 12

(cont)(cont)ScopeScope

Section 11 covers overall stability of the groundSection 11 covers overall stability of the groundand movements in the ground related toand movements in the ground related to

foundations, retaining structures, natural slopes,foundations, retaining structures, natural slopes,

embankments, and excavationsembankments, and excavations

Section 12 covers embankments for small damsSection 12 covers embankments for small dams

and infrastructureand infrastructure


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Supervision, monitoring, and maintenanceSupervision, monitoring, and maintenance

Slopes must be monitored whenSlopes must be monitored when

occurrence of limit states cannot be provenoccurrence of limit states cannot be proven

sufficiently unlikely by calculation or prescriptivesufficiently unlikely by calculation or prescriptive

measuresmeasures

assumptions made in calculations are not based onassumptions made in calculations are not based on

reliable datareliable data

Monitoring should provideMonitoring should provide

groundground--water levels or porewater levels or pore--water pressures forwater pressures for

effective stress analysiseffective stress analysis

lateral and vertical ground movementslateral and vertical ground movements

depth and shape of existing slide (for remedial work)depth and shape of existing slide (for remedial work)

rates of movementrates of movement


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Limits states for slopes and embankmentsLimits states for slopes and embankments

Limit states for slopes/embankments include:Limit states for slopes/embankments include:

Loss of overall stabilityLoss of overall stability

of the ground andof the ground and

associated structuresassociated structures

Excessive movementExcessive movement

Loss of serviceabilityLoss of serviceability


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Limits states for slopes and embankmentsLimits states for slopes and embankments

Section 12 adds for embankments:Section 12 adds for embankments:

Internal erosionInternal erosion

Surface erosion or scourSurface erosion or scour

Deformations leading toDeformations leading to

loss of serviceabilityloss of serviceability

damage to adjacent structuresdamage to adjacent structures

problems with transition zonesproblems with transition zones

Effects of freezing and thawingEffects of freezing and thawing

Degradation of base course materialsDegradation of base course materials

Deformations due to hydraulic actionsDeformations due to hydraulic actions

Changes in environmental conditionsChanges in environmental conditions


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Design situationsDesign situations

Design situations must consider:Design situations must consider:

Construction processesConstruction processes

Previous or continuing ground movementsPrevious or continuing ground movements

Effects of slope or embankment on existingEffects of slope or embankment on existing

structures or slopesstructures or slopes

VibrationsVibrations

Climatic variationsClimatic variations

Vegetation and its removalVegetation and its removal

Human or animal activityHuman or animal activity

Variations in water content or poreVariations in water content or pore--water pressurewater pressure

Wave actionWave action


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Design ApproachesDesign Approaches

Design Approach 1 applies partial factors toDesign Approach 1 applies partial factors to

actions in Combination 1actions in Combination 1

unfavourable variable actions and material properties inunfavourable variable actions and material properties in

Combination 2Combination 2


effects of actions and to resistanceseffects of actions and to resistances

but not to material propertiesbut not to material properties

different factors for favourable and unfavourable actionsdifferent factors for favourable and unfavourable actions


material properties and a small factor to variable actionsmaterial properties and a small factor to variable actions

but not to other actions or resistancesbut not to other actions or resistances

in DA3, all actions are treated asin DA3, all actions are treated asgeotechnicalgeotechnical

whenwhendesigning slopes and embankmentsdesigning slopes and embankments


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Design Approach 1 Combination 1Design Approach 1 Combination 1

for slopes and embankmentsfor slopes and embankments


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Design Approach 1 Combination 2Design Approach 1 Combination 2



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Design Approach 2Design Approach 2



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Design Approach 3Design Approach 3



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National choice of Design ApproachNational choice of Design Approach

15


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Partial factor groupingsPartial factor groupings

IndividualIndividual

partial factorpartial factor

or partialor partial

factorfactorgroupinggrouping

Design ApproachDesign Approach

11 22 33

Combination 1Combination 1 Combination 2Combination 2

GG 1.351.35 1.01.0 1.351.35 1.0*1.0*

G,favG,fav 1.01.0 1.01.0 1.01.0 1.01.0

QQ 1.51.5 1.31.3 1.51.5 1.3*1.3*

==

cc 1.01.0 1.251.25 1.01.0 1.251.25

ReRe 1.01.0 1.01.0 1.11.1 1.01.0

GG

xx

cc

xx

ReRe 1.351.35 1.251.25 1.4851.485 1.251.25

GG

xx

cc

//

1.351.35 1.01.0 1.351.35 1.01.0

G,favG,fav

xx

cc

//

1.01.0 1.01.0 1.01.0 1.01.0

QQ

//

GG 1.111.11 1.31.3 1.111.11 1.31.3

**Factor from Set A2 on geotechnical actionsFactor from Set A2 on geotechnical actions


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Implications of EC7 for slopesImplications of EC7 for slopes


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Key features of circular slip analysisKey features of circular slip analysis


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n

iii

n

ii

iiiii

QW

F

ubQWbc

F

0

0

sin

tan

tan1

tan'

BishopBishopss RoutineRoutine (aka(aka SimplifiedSimplified) Method) Method

partial factors applied

to material properties

partial factors

unfavourable

or favourable?partial factors

unfavourable onvariable actions


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Applying partial factors to BishopApplying partial factors to Bishops Methods Method

Applying partial factors is complicated by theApplying partial factors is complicated by theiterative nature of circular slip analysis (oriterative nature of circular slip analysis (ornonnon--circular)circular)

It is unclear what parts of the equation areIt is unclear what parts of the equation arefavourable or unfavourable at any point in thefavourable or unfavourable at any point in the

analysisanalysis

egeg

whenwhen

is negative the selfis negative the self--weight of the slipweight of the slipreduces the overturning momentreduces the overturning moment

There is therefore no fully logical way ofThere is therefore no fully logical way ofapplyingapplying

GG

andand

G;favG;fav

Applying different partial factors to differentApplying different partial factors to differentmaterials may result in a different mechanismmaterials may result in a different mechanism


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Current developments in EC7 andCurrent developments in EC7 and

NCCI documentsNCCI documents


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Developments in EC7Developments in EC7

TC250 SC7 is the CEN committee responsible for EC7. TheTC250 SC7 is the CEN committee responsible for EC7. Themaintenance submaintenance sub--committee considers:committee considers:

all matters associated with the development of the codeall matters associated with the development of the code

Collecting errors and ambiguities in the current textCollecting errors and ambiguities in the current text

ReRe--writing some sections where different EN documentswriting some sections where different EN documentscontradict each other, e.g. Anchoragescontradict each other, e.g. Anchorages

Producing corrigendum and eventually further versions of theProducing corrigendum and eventually further versions of thecodecode

ETC10 is responsible for the evaluation of EC7ETC10 is responsible for the evaluation of EC7

Assessing current best practice and interpretation of the codeAssessing current best practice and interpretation of the code

Has produced a set of standard design examples forHas produced a set of standard design examples forcomparative purposescomparative purposes

No major changes currently proposed for Sections 11 andNo major changes currently proposed for Sections 11 and12 of EN 199712 of EN 1997--11


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ETC10 examplesETC10 examples

ETC10 has produced a set of examples for engineers toETC10 has produced a set of examples for engineers to

apply EC7 principles, please visitapply EC7 principles, please visit www.eurcode7.com/etc10www.eurcode7.com/etc10

and attempt problems, closing date end of December 2009and attempt problems, closing date end of December 2009
http://www.eurcode7.com/etc10http://www.eurcode7.com/etc10http://www.eurcode7.com/etc10http://www.eurcode7.com/etc10http://www.eurcode7.com/etc10


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NCCI documentsNCCI documents

Documents containing NonDocuments containing Non--

conflicting complementaryconflicting complementary

information (information (NCCIsNCCIs) are) arebeing produced based onbeing produced based on

current British Standardscurrent British Standards

and other recognisedand other recognised

guidance documents e.g.guidance documents e.g.CIRIA C580, SpecificationCIRIA C580, Specification

for Highways Worksfor Highways Works

Of particular relevance toOf particular relevance to

slope engineering are BSslope engineering are BS60316031 --

Earthworks and BSEarthworks and BS

80068006

StrengthenedStrengthened

reinforced soils and otherreinforced soils and other

fills + BS5930, BS1377 etcfills + BS5930, BS1377 etc


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DPC BS 6031DPC BS 6031 -- EarthworksEarthworks

A draft of BS 6031 has been produced but is now closed for publiA draft of BS 6031 has been produced but is now closed for publicccommentcomment

It suggests that Design Approach 1 Combination 2 should be usedIt suggests that Design Approach 1 Combination 2 should be usedfor slopesfor slopes

The overall stability of slopes should be checked against DA1The overall stability of slopes should be checked against DA1Combination 2. For completeness, DA1 Combination 1 should also bCombination 2. For completeness, DA1 Combination 1 should also beechecked if the designer considers that the loading applied to thchecked if the designer considers that the loading applied to the slopee slope(other than the mass of the ground in the slope) might control t(other than the mass of the ground in the slope) might control thehefailure mechanism rather than the ground strength parametersfailure mechanism rather than the ground strength parameters (DPC(DPCBS 6031BS 6031 7.3.3)7.3.3)

A minimum surcharge load of 10 kN/mA minimum surcharge load of 10 kN/m22 should be applied to theshould be applied to thesurface at the top of embankments and cuttings where the externasurface at the top of embankments and cuttings where the externallaction might adversely affect the stability of the slope.action might adversely affect the stability of the slope. (DPC BS 6031(DPC BS 6031

7.2.3)7.2.3)

Combination 1 should only be used where there are large externalCombination 1 should only be used where there are large externalforces acting on the slope. A three stage method has beenforces acting on the slope. A three stage method has beensuggested by Frank et al but this results in an equivalent factosuggested by Frank et al but this results in an equivalent factor ofr of

safety of at least 1.35 for the effective stress casesafety of at least 1.35 for the effective stress case


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DPC BS 6031DPC BS 6031 Earthworks, partial factorsEarthworks, partial factors

The partial factors given in the NA annex to BSThe partial factors given in the NA annex to BS

EN1997 should be used in routine work coupledEN1997 should be used in routine work coupled

with the other recommendations of EC7 forwith the other recommendations of EC7 for

selection of design parametersselection of design parameters

BS 6031 points out that the partial factors mayBS 6031 points out that the partial factors may

not be adequate where the risk of any slopenot be adequate where the risk of any slopefailure is very high and may be too high forfailure is very high and may be too high for

situations where residual strength is adoptedsituations where residual strength is adopted

inin

this case it recommendsthis case it recommends

= 1.1= 1.1


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DPC BS 8006DPC BS 8006 Strengthened reinforcedStrengthened reinforced

soilssoils

DPC BS 8006 statesDPC BS 8006 states

BS EN 1997BS EN 1997--1:2004 does not cover the design and1:2004 does not cover the design and

execution of reinforced soil structures; the values ofexecution of reinforced soil structures; the values of

partial factors and load factors given in BS EN 1997partial factors and load factors given in BS EN 1997--

1:2004 have not been calibrated for reinforced soil1:2004 have not been calibrated for reinforced soil

structures. BS EN 1997structures. BS EN 1997--1:2004 should not be used in1:2004 should not be used in

the design and execution of reinforced soil. In the UK,the design and execution of reinforced soil. In the UK,

the design and execution of reinforced fill structuresthe design and execution of reinforced fill structures

should be carried out in accordance with BS 8006should be carried out in accordance with BS 8006--1 and1 and

BS EN 14475:2006. The partial factors set out in BSBS EN 14475:2006. The partial factors set out in BS

80068006--1 should not be replaced by similar factors in BS1 should not be replaced by similar factors in BS

EN 1997EN 1997--1:2004.1:2004. (DPC BS 8006(DPC BS 8006 5.1)5.1)


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Adapting to EC7 and use ofAdapting to EC7 and use of

softwaresoftware


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Adapting to EC7 and use of softwareAdapting to EC7 and use of software

Essentially if Design Approach 1 Combination 2 isEssentially if Design Approach 1 Combination 2 isused very little change is required except forused very little change is required except for

Multiplying unfavourable variable actions by 1.3Multiplying unfavourable variable actions by 1.3

Ensuring that the characteristic parameters and theEnsuring that the characteristic parameters and thedesign situation are appropriately conservativedesign situation are appropriately conservative

Software does not need to be modifiedSoftware does not need to be modified --

applyapplythe partial factors to obtain design materialthe partial factors to obtain design materialproperties and variable actions. As long as theproperties and variable actions. As long as theresultant factor of safety quoted by the programresultant factor of safety quoted by the program

isis

1.0 then the design complies with EC71.0 then the design complies with EC7

The above only checks the ULS limit state, whereThe above only checks the ULS limit state, wherenecessary the SLS limit state must also benecessary the SLS limit state must also beverifiedverified


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BS EN 1997 is already a current standard to whichBS EN 1997 is already a current standard to which

projects may be designedprojects may be designed

By March 2010 all conflicting standards will beBy March 2010 all conflicting standards will be

withdrawnwithdrawn

For slopes Design Approach 1 Combination 2 isFor slopes Design Approach 1 Combination 2 is

recommendedrecommended

Combination 1 may be ignored for slope design exceptCombination 1 may be ignored for slope design except

where external loading is highwhere external loading is high

Care should be exercised in using the BS EN partialCare should be exercised in using the BS EN partialfactors for all design situations and risk levelsfactors for all design situations and risk levels

Current relatedCurrent related BSsBSs

are being updated to removeare being updated to remove

conflicts or withdrawnconflicts or withdrawn


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To be kept upTo be kept up--toto--date on the developments ofdate on the developments of EurocodeEurocode

77

www.eurocode7.comwww.eurocode7.com

For discussion on the application ofFor discussion on the application of EurocodeEurocode

7 see7 see

Bond & Harris (2008), DecodingBond & Harris (2008), Decoding EurocodeEurocode

7, Taylor and7, Taylor andFrancisFrancis

Frank R.,Frank R., BauduinBauduin

C., Driscoll R.,C., Driscoll R., KavvadasKavvadas

M. and KrebsM. and KrebsOvesenOvesen

N.N. DesignerDesigners Guide to EN 1997s Guide to EN 1997--1:1: EurocodeEurocode 7:7:Geotechnical DesignGeotechnical Design General Rules.General Rules. Thomas Telford.Thomas Telford.

Department of Communities and Local GovernmentDepartment of Communities and Local Government

(2007).(2007).A designerA designers simple guide to BSEN 1997.s simple guide to BSEN 1997.London..London..((www.communities.gov.uk/planningandbuildingwww.communities.gov.uk/planningandbuilding).).

Driscoll R., Scott P. and Powell J. (2009)Driscoll R., Scott P. and Powell J. (2009) EurocodeEurocode 7:7:

implications for UK practice.implications for UK practice. CIRIA C641.CIRIA C641.
http://www.communities.gov.uk/planningandbuildinghttp://www.communities.gov.uk/planningandbuildinghttp://www.communities.gov.uk/planningandbuilding