Simple Guide to Eurocode 7-Libre

8/12/2019 Simple Guide to Eurocode 7-Libre

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January 2007

Dpartmnt for Communitis and Local Govrnmnt: London

A Designers Simple Guide

to BS EN 1997


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On 5th May 2006 the responsibilities of the Office of the Deputy Prime Minister (ODPM)

transferred to the Department for Communities and Local Government

Department for Communities and Local Government

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SW1E 5DU

Telephone: 020 7944 4400

Website: www.communities.gov.uk

A Designers Simple Guide to BS EN 1997 December 2005

It should be noted that this guidance has been based on the published

Eurocode, BS EN 1997-1:2004, together with the draft of its National Annex

that was available at the time of writing

Crown Copyright, 2006

Copyright in the typographical arrangement rests with the Crown.

This publication, excluding logos, may be reproduced free of charge in any format or medium

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ONTENTS

CHAPTER 1 A DESIGNERS SIMPLE GUIDE TO BS EN 1997 7

1.1 Introduction to the new EU geotechnical

Codes and Standards 71.2 About this Guide 9

1.3 Some basic points about BS EN 1997 11

CHAPTER 2 A BRIEF OVERVIEW OF BS EN 1997-1 -

GEOTECHNICAL DESIGN, GENERAL RULES. 14

2.1 Introduction 14

2.2 The design philosophy of BS EN 1997-1 172.2.1 Limit states 17

2.2.2 Design Requirements 182.2.3 Design Situations 22

2.3. Geotechnical design methods 222.3.1 Ultimate Limit State Design by Calculation 222.3.2 Calculations for STR and GEO Ultimate Limit State design 252.3.3 Performing Serviceability Limit State design checks 262.3.4 Design by Prescriptive Measures 272.3.5 Design using load tests and tests on experimental models 272.3.6 Design using the Observational Method 27

2.4 The Geotechnical Design Report 28

CHAPTER 3 OBTAINING GEOTECHNICAL DESIGN INFORMATION 30

3.1 Introduction 30

3.2 Using prEN 1997-2 to obtain ground parametervalues from tests 303.2.1. Introduction 303.2.2 Geotechnical Investigations 313.2.3. Soil and rock sampling and groundwater measurements 333.2.4. Field tests in soil and rock 34

3.2.5. Laboratory tests in soil and rock samples 343.2.6. The Ground Investigation Report 35

3.3 Characteristic values of geotechnical parameters 353.3.1. Characteristic values depend on failure mode 393.3.2. Other attempts to express uncertainty in

ground parameter values 393.3.3. Significance of statistical methods 403.3.4. Characteristic values of stiffness and weight density 40


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CHAPTER 4 DESIGN CALCULATIONS FOR FOUNDATIONS

AND RETAINING STRUCTURES 42

4.1 Introduction 42

4.2 Using Design Approach 1 in GEO andSTR ULS calculations 42

4.2.1 Combination 1 444.2.2 Combination 2 44

4.3 Spread foundations 454.3.1 Overall Stability 454.3.2 Design of the foundation 45

Example 4.1. 48

Example 4.2 57

4.4. Piles 62

4.4.1 General 624.4.2 Calculating ultimate compressive resistance

using ground parameters from tests 644.4.3 Vertical displacements of pile foundations

(serviceability of supported structure) 684.4.4 The structural design of piles 694.4.5 Aspects of the construction of piles 69

4.5 Anchorages 69

4.6 Retaining structures 694.6.1 Introduction 69

4.6.2 Limit States 694.6.3 Actions, geometrical data and wall friction 704.6.4 Design and construction considerations 72

Example 4.3 76

Example 4.4 82

Example 4.5 86

Example 4.6 94

Example 4.7 102


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CHAPTER 5 OTHER GEOTECHNICAL DESIGN AND CONSTRUCTION

MATTERS 110

5.1 General 110

5.2 Overall stability 1105.2.1 Limit States 110

5.2.2 Actions and design situations 1115.2.3 Design and construction considerations 1115.2.4 Ultimate limit state design 111

5.3 Design of embankments 1125.3.1 Limit States 1125.3.2 Actions and Design Situations 1125.3.3 Design and Construction Considerations 1125.3.4 Ultimate Limit State Design 1125.3.5 Serviceability Limit State Design 1125.3.6 Supervision and Monitoring 112

5.4 Supervision of construction, monitoring & maintenance 1135.4.1 Introduction 1135.4.2 Supervision 1145.4.3 Checking ground conditions 1145.4.4 Checking construction 1145.4.5 Monitoring 114

5.5 Fill, Dewatering, Ground Improvementand Reinforcement 1145.5.1 Introduction 1145.5.2 Fundamental requirements 115

5.5.3 Constructing with Fill 1155.5.4 Dewatering 1165.5.5 Ground improvement and reinforcement 116

CHAPTER 6 EUROPEAN GEOTECHNICAL CONSTRUCTION

STANDARDS 117

6.1 Introduction 117

6.2 Compatibility between BS EN 1997-1and Execution Standards 118


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6

CHAPTER 7 HOW THE NEW GEOTECHNICAL CODES AND

STANDARDS WILL BE APPLIED AND MAY IMPACT

ON UK PRACTICE 120

7.1 Introduction 120

7.2 How the BS ENs will be implemented 120

7.2.1 The UK National Annexes 1207.2.2 Withdrawal of BS codes and Standards. 121

7.3 A timetable for change 121

7.4 How the BS ENs may be applied 122

CHAPTER 8 REFERENCES AND BIBLIOGRAPHY 123

CHAPTER 9 APPENDICES 126

9.1 Contrasting design philosophies 126

9.2 The three alternative Design Approaches 127

9.3 The other Ultimate Limit States 130

9.4 The correspondence for ground investigation andtesting between BS documents and BS EN documents. 131

9.5 Significance of statistical methods 134

9.6 Calculating pile ultimate compressive resistanceusing static load tests 135

9.7 Calculating pile ultimate compressive resistanceusing the results of dynamic testing 137

9.8 Tensile resistance of piles 138


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Introduction to the new EU geotechnical Codes and Standards

7

1. A DESIGNERS SIMPLE GUIDE TO BS EN 1997

1.1. Introduction to the new EU geotechnical Codes and Standards

The current suite of BS Codes and Standards will, in due course, be

almost entirely replaced by a system of Eurocodes and Standards (ENs1

)published by BSI as BS ENs; it is expected that the replacement will be

complete by about 20102.

The Eurcodes adopt, for all civil and building engineering materials andstructures, a common design philosophy based on the use of separate

limit states3 and partial factors, rather than globalfactors (of safety); thisis a substantial departure from much traditional geotechnical design

practice as embodied in BS Codes such as BS 8004. Furthermore, thegeotechnical design Eurocode (BS EN 1997-1) provides one, unified

methodology for all geotechnical design problems; an advantage of BS EN1997-1 is that its design methodology is largely identical with that for all ofthe structural Eurocodes, making the integration of geotechnical designwith structural design more rational.

Reaching agreement between the EU Member States on this unifiedgeotechnical methodology resulted in what might initially appear to be arather complicated system of equations for use in design calculations; inaddition, it led to the introduction of concepts and terminology that may not

be familiar to many designers of foundations and other geotechnicalstructures. For these reasons, it was felt appropriate to provide this Guide

to help people to interpret the new geotechnical Eurocode system ofCodes and Standards and to understand how this system will eventuallyreplace the current BS Codes and Standards.

1 The following abbreviations are used in this Guide:

BSI British Standards InstitutionCEN ComitEuropen de NormalisationECn Eurocode nEC7-1 Eurocode 7 Part 1, as contained in the DD ENV 1997-1:1995EN Euronorm (European standard)

BS EN British version of EuronormENV published European pre-standard (Vornorm in German)NAD National Application Document. The United Kingdom NAD

is contained in BSI publication DD ENV 1997-1:1995NA National Annex. The United Kingdom NA is contained in BSI publication BS

EN 1997-1:2005.

prEN Pre-norm - draft document circulated for comment but notgenerally published (similarly prENV)

SLS Serviceability Limit State

ULS Ultimate Limit State

2 The process of implementation of the BS ENs and an approximate time-table are discussed

in Section 7.3.

3 BS EN 1990 defines limit states as states beyond which the structure no longer fulfils the

relevant design criteria .

2 Th procss of implmntation of th BS ENs and an approximat tim-tabl ar discussd in

Sction 7.3.3

BS EN 1990 dfins limit stats as stats byond which th structur no longr fulfils thrlvant dsign critria.


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A Designers Simple Guide to BS EN 1997

8

f Ep f p f l , h pp fhm f w Mm S f h EU.Ov h fllw y, v p f pl hv wk p mmly-p f ppl l f mp f l hl, l f

l Eh p y CEN NlS B4 (BSI, ) f mplm. Th mpl f CEN Sl E hw Tl 1.1, h lly hv m f P ply v f vlpm. Th lkw h Bh v f h E p F. 1.15.

Th E f , hy wll y h h hk f .

Whl h p f h E wll m ly ll MmS, h levelf fy ppll m ply.Thf, h m h valuef pl (fy) f lf vl m. Eh E, N, wh

hw l mmy x. Th lm xp Nl Ax. Th h hlE, EN 1997-1, m l BS EN 1997-1 y hl f Nl Fw Nl Ax6. Th Nl

Ax S 7 f h G.

Number7: Name Subject

EN 1990 B f l

EN 1991 E 1 A

EN 1992 E 2 f

EN 1993 E 3 f l

EN 1994 E 4 f mp l

EN 1995 E 5 f m

EN 1996 E 6 f my

EN 1997 E 78 Ghl

EN 1998 E 8 f f hqk

EN 1999 E 9 f lmm

Table 1.1 Th f pmy l E

4

Th Nl S By m plh h E wh y h h x. Imy l p Nl Fw Nl Ax h mplm lqm h lly p y h Ep Cmm ( S 7)

5 p h f h pj, E 7 wll, f , wh

m f h h l ml E f h mpl pj .6N h whl BS EN 1997-1 w plh y BSI m 2004, Nl Ax

y vll.

7 Th CEN m EN 199x m BS EN 199x f pl y BSI.

8 E 7 f w P P 1 (BS EN 1997-1) - Geotechnical design Generalrules P 2 (pEN 1997-2) - Ground investigation and testing, y plh.


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9

1.2. About this Guide

Aims of the GuideTh G k

) v mpl xpl f h w 9f

mplmy hl , , v m h wll lly pl h f lBSI v h x fw y10;

) lfy h m f w mly, xpl ll mh h v xplly C, p y-- xpl f hw h wmh wk h mpl xmpl.

) xpl hw mplm h w f m mply wh h qm f h Bl Rl.

What the Guide contains.

Th G h fllw l S

2. A f vvw f BS EN 1997-1 - Ghl , ll.

3. O hl pm.

4. ll f f .

5. Oh hl m.

6. Ep hl

7. Hw h w hl C S wll ppl my mp UK p.

8. Rf Blphy.

9. App.

Th ppl pp f h G pv simple hp f BS EN1997-1 f h m mm plm hl p. Th G ff l, l-y-l, mmy h C pvppp f C l m11.

I m kp h G lly fl pl,m f h ml h l wh l mm hl

plm h mv fm h m y f x App;9

S S 1.3 F. 1.2

10 S S 7.

11A mphv G vll (Fk l, 2004). F l mm

h ml mm ll h E, h my f h I hDesigners' Guide to EN 1990 Eurocode: Basis of structural design(Glv l, 2002);h l pv fm h mplm f h l E h EU Mm S. A l k pp mplm Guidance PaperL (concerning the Construction Products Directive 89/106/EEC), Application and Use ofEurocodesy h Ep Cmm (2001).I , Appx A f h DesignersGuide to EN 1990v l fm h C P v, h EU

v wh whh ll h l l l h EU Mm S mmply.


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10

l, pplmy fm h pl F,whl fh fm hhlh Bx.

Thh h G mph pl vyy p, vmpl hl , h f h w p l f hl hpp BS EN 1997-1.

How to use the Guide.

Th G m j wh h C lf. Th Gh mwh ffly fm h C, whh lwy fllw ll q f , pph h G ly p l h C; -f, mp C l m v h h-h m f p ml12. Fh, y xp fm h Code hw italics. Th yml p hG h f BS EN 1997-1.

B h G h lly kp mpl pl, my h l l h m mh lk.M mphv xply ml k fm vll ( S 8).

Who its for.

I m h BS EN 1997 wll y f ll vl . Th E h w f y suitably qualified personnel with relevant experience. Th pm f h m , xp h qlf xp m ppp q f h pj h13.Th m pp f BS EN 1997-1 pv fmwk f Ppl h m m v l f hw pfm

. H xp wll l pqly h E l. BS EN 1997-1, hf hG, m h h h lvl f kwl xpf l mh hl ppp f h pj.

Th G h w f h ff yp f hp

) Th l hl wh my f hv C wh wll, vhl, h h mpl wh h Cqm;

) Th m pl, hl, wh mply

wll f plly-p pj f whh h E my ly; f h l f h E wll y.

) Th -hlly qlf wh my y mpl f mll pj f whh h plm, h hl

12

N h f clauses BS EN 1997-1 pEN 1997-2 ( S 3) hw italicswhl h pph h G hw ml yp f.

13 I m , hf, h q h h pfm hk f

BS EN 1997-1 l pv y qlf wh lv hl xp.


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11

pl fl q. Sh pj f lmll h vlpm wh h f my p 14 wh h hl q lvly h-fw (h mll wll ly BS 80021999).

1.3. Some basic points about BS EN 1997

E 7 f w P P 1 (BS EN 1997-1) - Geotechnicaldesign General rules P 2 (pEN 1997-2) - Ground investigationand testing. Bh h G, hh P 1 f m ly w h ppl l lly p.

I mp h ll f h m vhl h EU Mm S l h wP f BS EN 1997. Ally, hw F. 1.2, h wll S f h fl v , ly ,

f h f h x

15

f pl hl wk;h p y ff CEN Thl Cmm fmh h w EN 1997. Th l S f f lf w y ISO Thl Cmmwhh h h CEN ym. Th h S S 3 6.

14

Pp mh BS EN 1997-1; S 2.3.4

4.3.2.

15 Ex h Ep w f .


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12

BS EN 1990

BS EN 1991

BS EN 1992 BS EN 1993 BS EN 1994

BS EN 1995 BS EN 1996 BS EN 1999

BS EN 1997 BS EN 1998

Ppl f l fy,vly ly

A

Sp l

Ghl m

Fi ure 1.1 Th lk w h Sl E


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T

Sp

i

Other StructuralEurocodes

e.g. EN 1993-5

Geotechnical

Projects

Geotechnical DesignEurocodes:

BS EN 1997-1;prEN 1997-2

Figure 1.2: Diagrammatic representation of the suite of EU geotechnical and structural Cod

EuropeanStandardsfor theExecution ofSpecialGeotechnicalWorks

Eurocodes: Basisof Structural Design(BS EN 1990) and

Actions onStructures (BS EN

1991-1-1)


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14

2. A BRIEF OVERVIEW OF BS EN 1997-1 - GEOTECHNICALDESIGN, GENERAL RULES.

2.1. Introduction

BS EN 1997 h w P BS EN 1997-1 whh v Geotechnical

design general rules pEN 1997-2 whh v Groundinvestigation and testing. S 2 f h G BS EN 1997-1 whl S 7 v pEN 1997-2.

I mp pp h BS EN 1997-1 lhl ml pv fmwk f f hk h wll pfm fly; h ,h h wll h lm p . Th C hf pv, l, ll h lqm f hk . I pv ly lm fm hw pfm ll fh l my q fm h x, h l

mh k y pl.

BS EN 1997-1 h l Principles Application Rules16

f hl , pmly safety(q h ly), serviceability(pl mvm fm) durabilityf pp , h f l vl wk17 , f l k.

BS EN 1997-1 h fllw S

S 1 Gl

- S 2 B f hl

- S 3 Ghl - S 4 Spv f , m

m

- S 5 Fll, w, mpvm fm

- S 6 Sp f

- S 7 Pl f

- S 8 Ah

- S 9 R

- S 10 Hyl fl

16

Ppl my (Nmv) qm; Ppll h C f y Pf h l m h w hll. All h l Appl Rlh h m whh h my hw mply wh hPpl. Appl Rl Ifmv(.. my f fm ly) w h hl my.

17 BS EN 1997-1 my l v f m f h pj h h

f , m, l lp l, h f f f pl wk h l pw pl ffh , whh q ll h pv y h E.


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A brief overview of BS EN 1997 1 Geotechnical design, general rules

15

- S 11 S ly

- S 12 Emkm.

BS EN 1997-1 l h Ax Tl 2.1.

Table 2.1- Th Ax BS EN 1997-1Ax S Tl

A Nmv Pl lf f lm lm mm vl

18

Annex A wh Sections 6 12, v h lv pl l f, h mm vl, f lm lm .Annex A mv , whh m h lp f h h f m , lhh hvalues fmv my hf mf h Nl

Ax ( S 8).

B Ifmv Bk fm pl f f Apph 1, 2 3.

Annex Bv m k fm h h lv Apph pm y EN 1990 v EN 1997-1 (

Appx 9.2).

C Ifmv Smpl p m lm vl f

h p vl wll

Ifmv A mpl lylmh f ll.

E Ifmv A mpl m-mplmh f m.

F Ifmv Smpl mh f lm vl

G Ifmv A mpl mh f v pm fp f

k

Annexes C Gpvxmpl f lly ll mhf h f f ;

H Ifmv Lm vl f l fm fmvm.

J Ifmv Chkl f pv pfmm.

Annexes C J fmv ,whh m h ppl,hy my p hNl Ax ( S 8).

Th p f BS EN 1997-1 mp Tl 2.2 wh h BS hlC S h wll whw wh h E fllymplm; Tl 2.2 l p wh pEN 1997-2 h -

ll xBS EN h S 6 f h G.

18

ThAnnex fmvwhh m h h pl f l must ; hwv,h valuesf h f m f l m h vl hw h

Annex h ly mm.


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16

TABLE 2.2 Th f h Ep m h p wh BS C

New European DocumentsBS Code

BS EN 1997-1 prEN 1997-2

Section - Title

General issues

covered Section - Title1. Gl2. B f hl

Ovll Apph

BS 59301999 - Sv

3. Ghl G v

1. Gl2. Pl f v3. Sl k mpl w mm4. Fl l k5. Ly l k6. G v p

Ax B - Pl f hl v

Sm f h lw4. Spv f ,

m m p f v

BS 60311981 - Ehwk

(BS 80061995) -Sh/f l hfll;

5. Fll, w, mpvm fm.

(N h EC7-1 v h f f l h y l .

BS 80041986 -F

6. Sp f

BS 80041986 -FBS 80081996 Sfyp pf h f mh-hf f pl hpp

7. Pl f

BS 80811989 - Gh

8. Ah

BS 8002:1994 - Eh

9. R

Sm 10. Hyl fl

11. Ovll ly

BS 60311981 - Ehwk

12. Emkm

f pflm


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17

2.2. The design philosophy of BS EN 1997-1I h S w hll xm h l f f h phlphy h E hw ff fm h UK p p BS C. A BS EN 1997-1 lwy fllw ll q, h S fllw xly h f

p f x h C

19

.2.2.1 Limit statesBS EN 1997-1 lm ; h m h hmpl wh wll pv h f lm 20. A lm l, f xmpl,

f m h m l.

Whl h , hy, my lm h v, h f v fy w fmlly ff yp f lm ,h f hm hv w qm

lm lm (ULS); vly lm (SLS).

Ulm Lm SULS f states associated with collapse or with other similar formsof structural failure(.. fl f h f ff ). I hl , ULS l fl y xv fm, l f ly f h y p f . H, whh

p f m f f f lm h mvm hl ULS v f h lf h h h lm f h.

Ulm lm f fll llp flf hl fly q . Hwv, lm my vlp hpp f l plm f f, whh hlf fl. Th m, f xmpl, h f my l,f lly l ( h x ULS fl), p f hpp my hv fl (f xmpl, m h l llp w l fm h ). BS EN 1997-1 q h h pl v. BS EN 1997-1 h

w h fllw fv ff yp f ULS ym f hm19

Pph m h G ly p wh l m hC. T l G x wh C x, h m f mp Cl hw h h-h- f h p.

20 Lm f BS EN 1990 (Clause 3.1(1)P) y whh h

l f h pfm qm. Sly, h x f lm h pv, hh BS EN 1997-1 f f hk, pv v h occurrencef lm .


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18

h hw ( k)

l f qlm f h h , y, whh h h f l ml h f pv (EQU);

l fl xv fm f h llm, l f, pl, m wll, , whh hh f l ml f pv (STR) ;

fl xv fm f h , whh h h fl k f pv (GEO) , (.. vllly, f p f pl f);

l f qlm f h h plf y wp (yy) h vl (UPL) ;

hyl hv, l pp h yhyl (HY).

Th ULS xplly f BS C.

F m f h plm lkly y f hG, h STR GEO lm lm h h wll pply, hy v h f hllw pl f hmmhl . Th EQU ULS f h wh, f xmpl, wll, kf, l f 21 . Th UPL HYULS, whl m mm h EQU, lly y h f h G. Cqly, S 2.3.2 w hll STR GEO ULS ll whl h h ULS ly fly Appx 9.3.

Svly Lm SSLS f states that correspond to conditions beyond whichspecified service requirements for a structure or structural member are no

longer met(.. lm h xv f h pp f h ).S 2.3.3 l wh SLS .

2.2.2 General design requirements

Th C q m hk h pfm m f k

) lh h ( 2.2.3);

) fy h lv lm ;

21

A EQU ULS hk l f hw h vl hzl f, mm, qlm vl.


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19

) h f mh22, hk h h lm x f h .

I y h k, h k wh h pj mplxy f. T h, BS EN 1997-1 mmv pj Ghl C (GC) 1, 2 3 p

h pp f h ; h mplxy f h , h l h ; h lvl f k vlv; pv xp f h pl .

I F. 2.1 flw m ll h f hl BSEN 1997-1. If h f GC p, h hl hk h f h pj. Th h plm hl mlly v plmy p h v. Th hl h hk ply h h f h p, y h

k F. 2.1. Th p f hh my jfy m ml , wh h hm ppp.

Clauses 2.1(10)to 2.1(21)

M pj wll fll GC 2, whl vy mpl plm my GC1, wh mplx plm fll GC 3 23 ; F. 2.2 flw m hwh q f . Exmpl v f h yp f pj h h GC.

A GC mmh mply. GC l BS EN 1997 hlp lh h x f v q hm f ff p hk h fy.

Clauses2.1(14),2.1(19),2.1(21)

Clause3.2.1(2)P

22

Th hl hk h h lv lm x y

m f h fllw mh- f ll ( 2.3.1 2.3.2)- h p f ppv m ( 2.3.4), whh wll-lh

pv p wh ll wll-f l;

- ml fll l ( 2.3.5), whh plly fl h f pl h;

- h Ovl Mh ( 2.3.6).

23 Th C kwl h GC 3 plm hl q p y

pv (clause 2.1(20)).


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20

Figure 2.1: The design process of EN 1997-1 (the number in brackets, shown in itaic,refer to the relevant sections and clauses in BS EN 1997-1)

Establish preliminary GeotechnicalCategory of the structure (2.1(10))

Preliminary ground investigations(3.2.2)and check of Geotechnical Category

Design investigations (3.2.3)

Ground investigation report (3.4) and checkof Geotechnical Category

Sufficient information?

Design by calculations (2.4), prescriptive

measures (2.5), load or model tests (2.6), orobservational method (2.7)

Yes

No

Geotechnical design report (2.8) andreassessment of Geotechnical Category

Supervision of the execution of the work (4)and reassessment of Geotechnical Category

*

*

*

*

The *

signifies where

categorisation ischecked.

*


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Abriefov

erview

ofBSEN1997

1

Geotechnic

aldesign,generalrules

Figure 2.2:Flow chart for geotechnical categorisation (afterSimpson & Driscoll, 1998)

Is the structure small and relativelysimple?

Are ground conditions known fromcomparable local experience to be

sufficiently straight forward that routinemethods may be used for foundation

design and construction?

If excavation below the water table isinvolved, does comparable localexperience indicate that it will be

straightforward?

Is there negligible risk in terms ofoverall stability or ground movements?

Category 1

Is the structure ver lar e or unusual?

Does it involve abnormal risks?

Is there unusual or exce tionall difficult round?

Are there unusual or exce tional loadin conditions?

Is the structure in a hi hl seismic area?

Is the structure in an area of probable siteinstability or persistent ground movements?

Category 2 e.g. :

Spread foundations, raft foundations, pile foundations, walls andother structures retaining or supporting soil or water,excavations, bridge piers and abutments, embankments andearthworks, ground anchorages and other tie back systems,tunnels in hard, non fractured rock not subjected to special watertightness or other requirements.

yes

yes

yes

yes

no

no

no

no

no

no

no

no

no

no


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22

2.2.3 Dein Situation

Design situations are described as: persistent (long-term), transient (short-term) and accidental.

The selected design situation must be sufficiently severe and must cover all conditionswhich can reasonably be foreseeable during temporary (transient) construction worksand the (persistent) use of the structure. Different design situations may involvedifferent limit states

24.

BS EN 1997-1 presents a list of items for consideration when identifying designsituations.

Claue

2.2(2)

2.3. Geotechnical design methods

BS EN 1997-1 offers one method or a combination of four methods for design anddesign checking; Using calculations for ULS (see 2.3.1) and SLS (see 2.3.3); Using prescriptivemeasures (see 2.3.4); Using tests (see 2.3.5); Using the Observational Method (see 2.3.6).

Each of these is discussed in turn.

Claue 2.4

Claue 2.5

Claue 2.6

Claue 2.

2.3.1 Ultimate Limit State ein by calculationThe following principles apply:

the explicit identification of limit states; calculation of the destabilising (unfavourable) actions (or their effects) and of

stabilising (favourable) actions and resistances using design valuesof variables,these values generally being calculated as the product of a partial factorand a

characteristicvalue; for a particular ULS, the sum of destabilising actions (or their effects) must not

exceed the sum of stabilising actions and resistances.

The manner in which these principles apply differs somewhat from those in many of theBS Codes (see Appendix 9.1).

24

For an accidental situation involving exceptional circumstances, the structure may be requiredmerely to survive without collapsing; in this case serviceability limit states would not be relevant.


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23

ll BS EN 1997-1 vlv h fllw p

lh vl f ( Bx 2.1); lh vl f pp ( Bx

2.2);

f lm h m x (.. py vl fffl lm); p ll ml25 f h lv lm vly lm

; hw ll h h lm wll x.

BOX 2.1 A

A my f (l ppl h h ) plm ( l) h mp y h h, y h h . A my permanent(..lf-wh f ), variable(.. mp l lfl) accidental(.. mp l)26.

vl f (F) ll h l q

F= F Fp

wh

Fp h pv27

( h Fk) vl f ( fh ff f );

F h pl f f ( E, f h ff f ).

BS EN 1997-1 y h h h vl f m v h ppl f BS EN 1990; h vl f h h m

fm h pp p m k fm BS EN 199128.

Clause 2.4.6.1

Clause2.4.2(1)P

25

F h p, h ll ml q p h

(.. h py f f), h ff f h (.. mm hf h f) / h fm f h .

26 Th vl f h fm h m k fm BS EN 1991 whl BS EN

1997-1 l wh h f plm mp y h whh ff y h . Spf xmpl f hl v l S 4.

27 Th h vl f , Fk, m pv vl. A , plly

f vl, my hv h pv vl; f xmpl, wh h vl l m.28

A p (m 2005), m P f BS EN 1991-1 BS EN 1991-2 hv plh.


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24

BOX 2.2- G pp, G pp m fm h l f fm hlv h h k-ly f lm mm ffl f f lp29.

vl f pp hll h ll

X = Xk/ M

whXk h h vl f ml () ppy ( Bx

2.3);M h pl f f h ml ppy,

hll ly y h 30 .

Th vl f l hl ( h ff) ll vl f vl, h vl h

h p f pl f h ppy vl ( Bx 2.3) ly.

Th vl f l h p fh vl, ll h pp, pl f.

Clause2.4.6.2

BOX 2.3 Ch vl f pp

BS EN 1997-1 f h h vl selected as acautious estimate of the value affecting the occurrence of the limit stateconsidered. Eh w ph h l mp

Selected: mph h mp f jm, Cautious estimate m vm q, Limit state considered31.

Th h mh h m f hvl f pp, l h f 32. Th j ph S 3.3.

Clause2.4.5.2 (2)P

29

S 3 h q f pp.

30 Th C mpl h wh ly , hl pm hl hv

vl h wll pv lvl f fy p h ff y h m fh vl pl f vl (clause 2.4.6.2(3)).

31 Th h vl m l h lm . Th fh S 3.

32 Th f h wh h m f h vl f

ml pp; h m fm h wp ppl , f xmpl, whmy lvly hm ml mk h hq mfl. Sh pph f h lm lwy ppp h vlm f wll lm h ml hhly vl. I BS EN 1997-1 h f l mh my, lm lwy ppp wll hf fh hG.


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25

vl ll f h ULS SLS, hh hvl wll lly ff f h w . Th vlq f SLS f ql h h vl f pm(fmlly, pl f f 1.0 ppl), h fml why h m lwy .

2.3.2 Calculations for STR and GEO Ultimate Limit State designI q. A1 Appx 9.1, h f ULS BS EN1997-1 l h fllw qly

E R (2.5)

wh

E h vl f h m f h f h ff fhm;

R h vl f h p f h

/ 33

.

Clause 2.4.7Clause

2.4.7.3.1

I BS EN 1997-1, E fm h l xp

E = E {F Fp ; Xk/M ; } (2.6a)

R fm

R = R {F Fp ; Xk/M ; } (2.7a)

wh

Clause2.4.7.3.2

Clause2.4.7.3.3

h vl f ml ppy (.. h ph w l)34 .

Th xp E { ..} R { }, whh m f vlv hm l, my p vl wy ( Bx 2.4).

I h h m Xk/M h xp hfl f pp h h wh y 35 hl h h p, hl h h p fm h 36.

33

I m h vl f h w m h h m fml p

fm lhl p , l m m BS C fP. Th , h E, designvl ll fm characteristicvl partialf, hw Bx 2.1 2.2.34

BS EN 1997-1 h m ml , wh h yml . Sh wll, f xmpl, h lvl lp f h f, w lvl, lvl f hf w , xv lvl h m f h hl.

35 BS EN 1997-1 h m wh y pl f wh.

36 N h, f F h 1.0, h vl f h x h

vl , f M h 1.0, h vl f h ml ppy wll l h hh vl.


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26

BOX 2.4 ff wy f xp h ff f

h vlpm f EN 1997-1 h w mh hp fm f h xp (2.6a) (2.7a). I h m h Mm S f h EU, h E ph lv Apph(A) whh lhly ff

fm f h xp; BS EN 1997-1 ly f h lv,A-1, lkly pm h Nl Ax. A f xpl fh ff h h Apph v Appx 9.2whl m l xpl f h ppl f A-1 v S 4.2, wh Exmpl f .

2.3.3 Performing Serviceability Limit State design checks

Lm q h h f vly lm ffly mpl. Svly lm my hk wwy y ll h vl f h ff f h E (..

fm, ffl lm37, v .) mphm wh lm vl, C

38;

y mplf mh, mpl xp.

Clause2.4.8(1)

I ll vl f h ff f , f h pp wll mlly ql h h vl,h h F M vl wll ql 1.0.

A lv pfm vly hk ll, mplf mh my hw h ffly lw f f h h ml, kp fm wh h q

vly lm39

. Th mplf mh ppl BS EN 1997-1 p f, pl f . BS EN1997-1 v f wh ffly lw f f h40.

Clause2.4.8(2)

37

I wh ffl lm ll, m f pp lwh vl f fm ml hl , f y llv h pp.

38 Illy, lm vl f fm, C , hl pf qm f

h pp BS EN 1997-1 l (clause 2.4.9(3)P) f m k wh lh lm vl f mvm. I mp h lm vl lh llly pl l -p wh h f hpp . Uly v vl lly l m .

39 Th mplf mh q h x f mpl xp wh ml l

. Th qm lly h m whh h mplf mhmy ppl vl f fml .40

BS 8002 p ml f fm 1.2, f ffv ll, 3.0 lm h mvm f wll l ll.


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27

2.3.4 Dein by recriptive Meaure41

Prescriptive measures involve conventional an enerally conervative ruleinthe design, and attention to specification and control of materials, workmanship,protection and maintenance procedures.

Prescriptive measures usually involve the application of charts, tables and

procedures that have been established from comparable experience; theyimplicitly contain their own safety factor. Very often, the concept of allowablestress on the soilis used in these charts or tables. An example would be thetable of minimum widths of strip foundations given in Approved Document A tothe Building Regulations. These widths are based on allowable bearingpressures for the different ground conditions cited. The calculations of allowablepressure have an implicit factor of safetybased on comparable experience.

Prescriptive measures may be applied, for example, to deal with problems ofdurability, by specifying additional thickness to prevent the adverse effects of

corrosion loss, and to the local prescription of depth of footings to avoid seasonalvolume change in clay soil. Prescriptive, conservative procedures are quite

common for the routine design of piles in familiar ground conditions.

Claue 2.5

2.3.5 Dein uin loa tet an tet on experimental moelBS EN 1997-1 permits design based on the results of load tests; indeed, as we

shall see in Section 4.4, load testing is actively encouraged for the design ofpiles.

Claue 2.6

2.3.6 Dein uin the Obervational MethoBS EN 1997-1 introduces use of the Observational Method in which a design for

the most likely circumstances is reviewed in a planned manner during thecourse of construction and in response to the monitored performance of the

work42

.The Method has a number of important ingredients one of which is a precise planof monitoring and of any actions required as a result of the monitored

performance. The advantage of this method is that it facilitates design where aprecise prediction of the geotechnical behaviour is difficult, e.g. where the groundconditions are complex or not sufficiently well known or where time or costsavings may be obtained by reducing temporary works such as the propping of

retaining structures in excavations. The Observational Method allows optimisticor pessimisticassumptions to be checked by monitoring the actual behaviour.

A comprehensive explanation of the Observational Method has been provided byNicholson et al (1999).

Claue 2.7

41 Prescriptive measures can be applied in cases where calculation models are not available or

not appropriate. Partial factors are not intended to be used with prescriptive measures.42

The Observational Method has been defined as a continuous, managed, integrated process ofdesign, construction control, monitoring and review that enables previously defined modificationsto be incorporated during or after construction as appropriate. An essential ingredient is the pre-definition of modifications should they prove necessary.


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28

.4. The Geotechnical Design ReportUlk BS C, BS EN 1997-1 q h mp, ,ll l f h vf f fy vly must Ghl Rp, lv p f whh mustpv h l. Th lvl f l f Ghl Rp wll

vy ly, p h yp f . F mpl , lh h h hw F. 2.3 my ff. Th p myl pl f pv m, ppp.

Th w m mp p f h GR

- h G Iv Rp ( S 3);

- pl f y q pv m f43 ( S 5.7).

Clause 2.8

43

A hkl f m h hl mlly l h GR v BS EN 1997-1(Clauses 2.8(1)P, 2.8(2), 2.8(3) and 2.8(4)P).


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29

Figure 2.3: Simpl Gotchnical Dsign Rport (aftr Simpson & Driscoll, 1998)

Job Titl

New start housing development

Structur Rfrnc:

Strip foundations

Rports usd:

Ground invstigation rport (giv rf. dat)

Factual

Bloggs Investigations Ltd reportABC/123 dated 21 Feb 95

Intrprtation:

Ditto

Cods and standards usd (lvl of

accptabl risk)

Eurocode 7Local building regs

Dscription of sit surroundings:

Formerly agricultural landGently sloping (4)

Calculations (or indx to calculations)

Characteristic load 60 kN/m.Local experience plus LocalBuilding Regulations (ref.........)indicates working bearingpressure of 100kPa acceptable.Therefore adopt footings 0.6mwide, minimum depth 0.5m(Building Regs) but depth variesto reach cu60kPa test on

site

Sction through structur showing actions

Assumd stratigraphy usd in dsign with proprtis:

Topsoil and very weathered glacial till upto 1m thick, overlying firm to stiff glacialtill (cu6okPa on pocket penetrometer)

Information to b vrifid during construction.

Nots on maintnanc and monitoring.

Concrete cast on un-softened glacial tillwith cu60kPa (pocket penetrometer)

Job No. Sht no of..............

Mad by: Dat........................

Chckd by: Dat........................

Approvd by: Dat........................


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30

. OBTAINING GEOTECHNICAL DESIGN INFORMATION

3.1 Introduction

Th p f pm f BS EN 1997 pf vl p f h f Ep .BS EN 1997-1 ly l m h mh f designpm pEN 1997-244 T S45T Spf46h m hmh h h pm fm whh vl q. Th l f plh p T S Spf hw Tl A4.1, A4.2 A4.3 f Appx 9.4 whhl hw hw h BS EN TS mp wh BS59301999 BS 13771990.

3.2 Using prEN 1997-2 to obtain ground parameter values from tests

3.2.1 Introduction:pEN 1997-2 wll wh BS EN 1997-1 pv qm mm f hl v . Thv l

- h hy f vlpm h ;- ppl f x ;- h v.-pEN 1997-2 pmy l the acquisition, evaluation, assessment andreporting of geotechnical data required for design BS EN 1997-1 v.

pEN 1997-2 v- h pl p f v;- h f l k mpl;- h l qm f m f mmly ly

fl ,

UClause1.1.2(1)

44Elwh h G, f pf l BS EN 1997-1 hw, l, h h-h m f h p. I h S, f pf l pEN 1997-2 hw, h h-h m, UlUf.45

T S pfy hw hll pfm.46

T Spf v hw hl pfm. I xp hmy f h T Spf wll vlly v T S.


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Obtaining geotechnical design information

31

- h vl p f l,- h v f test results derived valuesf hl pm

ff. A v vl f the value of a geotechnicalparameter obtained from test results by theory, correlation or empiricism.A xmpl wl h h h hh l wh

qcvl m p . Cl my l hl lhp lk hl pm wh l, fxmpl wh vl f h l f h fmpm l fm ply x.

pEN 1997-2 pflly v vml v lyv mmly- fl ly . Th C lly hpl vlv ll p hl lyqlf. Th p l v BS EN ISO 22475-2 ( Appx 9.4,Tl A4.2).

I ppl pEN 1997-2 h v m h ll

lv ll47. p h qm, m f wh pEN 1997-2 mply p hl p v p.

Spf p f pEN 1997-2 w ply .

3.2.2 Geotechnical Investigations

BS EN 1997-1 h geotechnical investigations shall provide sufficientdata concerning the ground and groundwater conditions at and around the site

to enable a proper description of the essential ground properties and a reliableassessment of the characteristic values of the geotechnical parameters to beused in design calculations. Ghl v shall pfm.

UClauses

U1.1.2(2)

Uand1.1.2(3)

pEN 1997-2 f h fllw hhy f v- Ghl v, whh v h

fm h ,- G v, whh fl v, ly

k f hl ll fm, - Fl v, whh v (ll, mpl

l p) v ( , h h CPT).

pEN 1997-2 h Ground investigations shall provide a description ofground conditions relevant to the proposed works and establish a basis for the

assessment of the geotechnical parameters relevant for all constructionstages.

47

Th C h 'Geotechnical investigations shall be planned in such a way as to ensurethat relevant geotechnical information and data are available at the various stages of the project.Geotechnical information shall be adequate to manage identified and anticipated project risks.For intermediate and final building stages, information and data shall be provided to cover risks ofaccidents, delays and damage'.


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Wh h m f hl v pEN 1997-2v ph pph f v mp

- preliminary investigationsf h p plmy f h,

- design investigations,- controlling and monitoringv.

pEN 1997-2 h the provisions in the document are based on thepremise that the results from investigations recommended in one phase areavailable before the next phase is started. Hwv plplmy v h m m.

UPlmy vTh plmy v hl pl h wy h q - h vll ly l ly f h ;

- h ly f h mp wh lv ;- h l p f h ;- vl h pl ff f h pp wk , h

h l, ;- fy w ;- h pl f mh y mpvm;- pl h l v, l f f h

x f whh my hv f fl h hv fh .

Uclause3.2.1(1)P

U

ClausesU2.3 to 2.5U

A plmy v wl mlly l- k f hl ll fm h

, l p f pv v h vy,- fl (wlk-v vy), - f xp h vy,

ll, h C , l

the following estimates of soil data concerning, if relevant:- the type of soil or rock and their stratification;- the groundwater table or pore pressure profile;- the preliminary strength and deformation properties for soil and rock;- the potential occurrence of contaminated ground or groundwater that might

be hazardous to the durability of construction material.

U IvpEN 1997-2 h ..where the preliminary investigations do not

provide the necessary information to assess the aspects mentioned ..,complementary investigations shall be performed during the design

UClause2.4.1.1U


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33

investigation phase. v h m hlv h q f f h hmpy pm wk. Thy l pv hfm q f fy y ffl h my .

v mlly l fl v ly. Fl v mlly mp

- ll / xv ( p l hf h) fmpl;

- w mm;

- fl , lly .

pEN 1997-2 v h pl f h fl ly. G f h pplly f mmly fl v.G pv h m yp f mpl h ly.

v hl l hh ll h fm h lkly lv h pl 48.

UCl IvCl v p h ph hk mp h l whh m h .

Th l qm f p p BS EN 1997-1 mplm pEN 1997-2. Thy l h p h h h

l f h p.

Th l f h v m p ll lv pl( 3.2.6).

3.2.3 Soil and rock sampling and groundwater measurements

Section 3f pEN 1997-2 v h k f mpl f l, k w. I q fmy wh BS EN ISO 22475-1 ( Appx9.4, Tl A4.2) ll mpl mh.

USl mplTh qly l49 m f mpl v m h m f h hl v, h ly f h h mplxy f h pj.

88

48Sm h p ph f v pv pEN 1997-2.

49 Sl mpl f ly v fv qly l wh p h l

pp h m m h mpl hl, p ; h qly l f pEN 1997-2.


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34

Th f mpl mh f BS EN ISO 22475-150

lk h mpl qly l. Th q mpl qly wh h ly pfm h mpl. I lly h f pf mpl mh mpl f h hh qly l wh h mh. F

ly h , h hh mpl qly q h ly hv wh f h mpl mh. I ff, pEN 1997-2l h mh f ll mpl p hv hq qly f l pm m h ly.

UGwpEN 1997-2 v ly h mm f p w p h pv lv mph p. I q h mm y mpl wh BS EN ISO 22475-1.

Mm m m fqy h h v pply qpm m l ll llw h

. Th C h pf p qm v vh BS EN ISO 22475-1.

3.2.4 Field tests in soil and rockpEN 1997-2 v ( Appx 9.4, Tl A4.1) hw l. Th m k p wh h p T S f EN ISO 22476 (

Appx 9.4, Tl A4.2)51. Th vl f l m llvll l fm.

I l qm h h ff m f ll plhl qpm fl h m pm. Ifl v hl pm ff, hvly h ly f y lhp m vl lly. Iff, h vl f l q jf.

Spf qm mm l vl v fh mh, fllw y xmpl f h f h l, hv (f ppll) v vl h f BSEN 1997-152.

3.2.5 Laboratory tests in soil and rock samples

pEN 1997-2 mp qm f h ly f mpll h BS EN ISO 22475-1.

F h p f v ( Appx 9.4, Tl A4.2),

50

I qm h hl, p f mpl hll wh BS EN ISO 22475-1.

51 If Thl Spf, h h T Spf, ppl h h p

hl flfl l qm.

52 Exmpl f l f v vl Ifmv Ax

( Appx 9.4, Tl A4.1).


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35

pf qm m . Th my pply mm, h p l y p v vl.

3.2.6 The Ground Investigation Report

pEN 1997-2 mk mply h pv f m fm f GIv Rp (GIR) p f h Ghl Rp (GR).Th C pf h h GIR m l

- p f ll vll hl fm lll f lv ;

- fl f ll fl ly v;

- hl vl f h fm, h mpm h p f h l;

- m f mh p ( h lv );

- ll lv fm hw v vl w m, ly l ;

- y kw lm h l.

Th GIR hl pp y y fh fl lyv, wh mm jfy h f h wk. Shppl hl mp y l pmm f h fhv .

O h vl f pm q f h f h pjhv q pEN 1997-2 m, k BS EN 1997-1 whh h fm vl f h lf ( F. 3.1)

3.3 Characteristic values of geotechnical parameters

O f h h f UK p l h p BS EN1997-1 f h vlf pp; f h , hl f h vl q fh xpl.

BS EN 1997-1 h Design values of geotechnical parameters (XBdB)shall either be derived from characteristic values using the followingequations:

X

d

= Xk/

M

or shall be assessed directly.

BS EN 1997-1 y ly h fllw h m f vl If design values of geotechnical parameters are assessed directly,the values of the partial factors recommended in Annex A should be used asa guide to the required level of safety.

Clause2.4.6.2(1)P

Clause2.4.6.2(3)


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Whl h E pm h m f vl llypl py h m f vl fm hvl. Th S f h G hf xpl hw hvl ( v vl h lv fm) Bx 3.1.

BOX 3.1 Ch vl

Th f characteristic valueh f h mvl p h p f f BS EN 1997-1.

Th mp vy f h vl m fm hf h py v pply pl f h vl ly f ml vl fpm. Thf, wh h lv f m hhlh v, h vl f h pl f

pf h Nl Ax BS EN 1997-1, so the selection of thecharacteristic value is the main point in calculations at which engineers are

to apply their skills and judgment, with the possibility of dangerous oruneconomic mistakes(Ahl)53.

Th p f m vl f h hl pm,fm ly / fl mm, hh h pplf y l p v vl f l h hl f h vl whh pl f ppl, h y h pEN 1997-2 BS EN 1997-1, ll F. 3.1;m l f h hw h w p p F. 3.1

Sp 1 lh h vl f h ppp pp;

Sp 2 fm Sp 1, l h h vl, l ll lv,mplmy fm.

M f h v vlv Sp 1 v y pEN 1997-2 hv S 3.2. I wh w fllw, w l wh Sp2.

Clause2.4.5.2(1)P

53

E hv lwy h h ply f l vl f ml pm fll. Th p h mm f lk , ffl fhlpfl v h hh p y ppp vl fm v h fm. I pl, h f vm y h vl f pp ly .


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Figure 3.1a - Gl fmwk f h l f derived, h design, vlf hl pp.

Typ f F= fl L= ly

Cl

Test results and

derived values

1 2 3 4

F 1 F 2 L 1 L 2

C1 C2

Cautious selection

Ghl ml hvl f hl pp

vl f hl

Application ofpartial factors

Ifmfm h

h , hl k h pj

EN 1997-1

EN 1997-2

m

lhw Sp 1 fF. 3.1

lhw Sp 2 fF. 3.1


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38

Figure 3.1b - Gl p f m h vl fmm vl

Measured ValuesUSTEP 1

Covered by:

BS EN 1997-1,Clauses 2.4.3,

3.3 and

prEN 1997-2

and testingstandards

Rlv plh ll lxp

Test Results

Rl f fl pl p h l ly pl pm

T l , pf y fh ly

Characteristic ParameterValue

C m f hl pm vlk f

Nm f l Vly f h Th f h l, ..

ppl f f pl l

Pl lm vlm f vlv N f h , ff

ly l

Sl f lv l .. pk vlm h

Am f fl f pm vl. Cl fppl l h pm l f l v vl fm l; ..

f v fm x-ymm pl

Bjm f f BBvl fm fl v

USTEP 2

Covered by

BS EN 1997-1,Clause 2.4 5.2

Geotechnical Parameter Values

Quantified for design calculations

Thy, mpl lhp l Derived values

Ch f ppp l wh l l pm

l


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39

Th h vl f hl ml pm m f h ml lly h h wy hml wll ff h pfm f h l pl lm . Fl ly , hy complemented by well-established experience. Th l

vl vly jv m x, fl y hkwl xp f h . I my , h kwly f m, x xp f , v fly f pm vl, wh l hk.

I l h h vl, m k f m fm h l BS EN 1997-1.

Hv k f ll h , BS EN 1997-1 fh vl fllw thecharacteristic value of a soil or rock

parameter shall be selected as a cautious estimate of the value affectingthe occurrence of the limit state.

Eh w ph h f mp

selected: mph h mp f jm, cautious estimate m vm q, limit state considered Th l vl m l h lm

m f pl fl.

Clause2.4.5.2(1)P

Clause2.4.5.2(4)P

Clause2.4.5.2(2)P

3.3.1. Characteristic values depend on failure mode

T ll hw h w affecting the occurrence of the limit statemhpply, h h h vl f pm m ly h m f w ff lm . I my

p h x whh pl fl m v hvl pp f h m, ll Bx 3.2.

3.3.2. Other attempts to express uncertainty in ground parameter values

I hlpfl mp h m f vv pm BS EN 1997-1 wh pph h hl .

CIRIA Rp 580 (G l, 2003) h my moderately conservative valuesf pm; mlyvv f m f h vl lv h f h lm . Th p h

qvl representativevl f BS 8002 (1994) characteristicvl f EC7.

I BS 8002, vl f l h (.. vl ll) v y f pvvl. Apv vl f vv m f h mh f h l. Cvv vl fh f vl fl pm whh m v h h m lkly vl. Thymy l ( ) h h m lkly vl. Thy w h


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40

limit of the credible range of values.

BOX 3.2 Characteristic value and failure mode

Figure 3.2 - Small building on estuarine beds near slope

Figure 3.2 shows a small industrial building, founded on pad footings neara long slope. The underlying materials are estuarine beds, mainly of sandswith some impersistent lenses of clay occurring at random. In this type ofsituation, the designer could, for designing the footings, assume that all ofthem are founded on clay, the most adverse circumstance

54. When the

designer considers the overall stability of his building, and hence thepossibility of a slope failure along the large slip surface illustrated, it seemsinconceivable that this surface will lie entirely, or even mainly in clay. It cantherefore be seen that, in this example, there could be more than onecharacteristic value for strength parameters of the samesite, with a

selection for the footing design that is different from that for the slip surface.

3.3.3. Significance of statistical methodsBS EN 1997-1 alludes to the employment of statistical approaches to theselection of characteristic values (see Appendix 9.5). However, for the majorityof projects the use of statistics will not be appropriate. The exception may bewhere a large amount of high-quality ground investigation data is available.

Clause2.4.5.2(10) &

(11)

3.3.4. Characteristic values of stiffness and weight densityBS EN 1990 states that The structural stiffness parameters (e.g. moduli ofelasticity ) . should be represented by a mean value.

The context of this definition is ULS structural design, in which values ofstiffness are needed for analysis, but they rarely play a dominant part indetermining the occurrence of a limit state. In problems involving ground-structure interaction, however, the stiffness of the ground is often a veryimportant parameter. In these cases, the use of a mean value for stiffness isquestionable, since the calculations would then imply a 50% probability that

BS EN 1990,clause 4.2(8)

54

Alternatively, he could require an inspection and probing at each footing location, soavoiding this most conservative assumption.


41/139


41

h lm wl x, f h v l. If h lm SLS f whh plm v,pl l f wl y, plm ll m vlff wl m, wh m f y.I p, ly k h pph, pf mk

m pm m wh h f y.

BS EN 1997-1 hf h m f f h vl fff f h. Th , m, m vl.

BS EN 1997-1 f f h vl l ppl h why f l k. Hwv, h y wh y lly ffly lw h h mk wm vl. F fll ml h wll, plhk q.

Clause9.3.1.2


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42

4. DESIGN CALCULATIONS FOR FOUNDATIONS AND RETAININGSTRUCTURES

4.1. Introduction

BS EN 1997-1 pm vl mh f , ll f whh l

pfm l ll, h ppv m, h fml l h ppl f h Ovl Mh (S 2.3.6). I h S, w xm h f ll h C h hw ppl hfw f (f h GEO STR lm lm ) f SLS .

4.2. Using Design Approach 1 for GEO and STR ULS calculations

W hv S 2.3.2 h BS EN 1997-1 wll p A-1 whhh w fml xp

E = E {FBFp ; Xk/M ; } (2.6a)

R = R {F Fp; Xk /M; } (2.7a)

fy h qly E R. (2.5)

(N h fh xp (2.7b)

R = R {FFp; Xk; }/R

A-1 f pl h. Th ppl f Rh h ml f).

I ppl, A-1 q w p ll pfm whhh GEO STR ULS xm w ff combinationsf f pl f55 . Th m w , h yml xpl Appx 9.2. Th valuesmm f ll h pl h f EN 1997-1 h TablesAnnex A.

A my f h vl h 17 Tl hv lv f A-1, hf vl f A-1, f h GEO STR ULS, hv ml h l Tl 4.1 lw, f mply ly.

clause2.4.7.3.2(1)

clause2.4.7.3.3(1)

55

Th qm f w p ll, ppl, pfm f ll vlv h m-m h h ly f vlpmf h l E h f h l mm mhly. A fll xpl my f Smp & ll, 1998.


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Designcalculationsforfoundationsandretainingstructures

Table 4.1 -- Values of partial factors recommended in BS EN 1997-1Annex A

Design Approach 1

Combination 1 Combination 2 Piles & Anc

[Note: The spaces shown in grey contain factor values = 1.0, as maybe seen in the TablesinAnnex A)

A1 M1 R1 A2 M2 R1 A2

unfav 1.35 1.0 1.0Permanent - G

fav 1.0 1.0 1.0

unfav 1.5 1.3 1.3

A(Action)values

(F)

Factors on

Actions(or theEffects ofactions) Variable - Q

fav 0.0 0.0 0.0

tan 1.0 1.25

Effective cohesion c 1.0 1.25

Undrained strength cu 1.0 1.4

Unconfined strength qu 1.0 1.4

M(Material)values

(M)

Factors ongroundproperties

Weight density 1.0 1.0

Base b 1.0Drivenpiles

Shaft (compression) s 1.0

Total/combined(compression)

t 1.0

Shaft in tension s;t 1.25

Base b 1.25Boredpiles


Total/combined(compression)

s 1.15


Base b 1.1CFApiles


Total/combined(compression) s 1.1


AnchorsTemporary a;t 1.1

R(Resistance)values

(R)

Permanent a;p 1.1


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44

4.2.1. Combination 1Th xp ymllly

A1 +M1 +R1

wh- h yml Ap h f pl f f h F f

h ff f E;

- h yml Mp h f pl f Mf h

(ml) pm f h .

- h yml Rp h f pl f f R(xp2.6b).

- h yml + m m wh.

Tl 4.1 (S A1) G = 1.35 Q = 1.556

. Cll f

fm h pfm vl f

pp ql h h vl Tl 4.1 (S M1) = = = q= = 1.0 whl h, Cm 1,

ppl pmly h l .

4.2.2. Combination 2Th Cm v h whh ppl pmly pp57.

Cm 2 xp ymllly

A2 +M2 +R1

whh h pm fm h h pv vl(G = 1.0, S A2, Tl 4.1) whl y fvl, vl fm h

, y lvly mll m, v h pvvl (Q = 1.3, S A2, Tl 4.1). Cll f fm

h pfm vl f pp lw hh vl (= =1.25, = q= 1.4, S M2, Tl 4.1), whl y

fm h wh f h h vl (= 1.0 , S

M2, Tl 4.1), h l y wh y hh h.

S A-1 fm h lly ll

f ml pp ( M) fm hl

56

N h, whl h yml f pl f f h ff f ,pvly, F E, G Q h pf yml f pm vl ,

pvly. Fh, h f f fvl, l p h G;,

whl h f f fvl, l hv h yml G; .

57 Uy hw wll h ll ml l hv l

m v y h pl f vl f Cm 2.


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Design calculations for foundations and retaining structures

45

element resistances, the resistance factors, R, (set R1) are not used. However, as

we shall see later, the design of piles and anchorages is a notable exception to thisgeneral rule.

Where it is obvious that one Combination will govern the design, it is not necessary

to perform calculations for the other see Box 4.1.

BOX 4.1 Application of Combinations 1 & 2

In many circumstances, the dimensionsof a foundation are determined from theCombination 2 calculation, while the structural design (i.e. the bending momentsand shear forces) is determined using the Combination 1 calculation with thedimensions found from Combination 2. A suggested, initial procedure is firstly toperform the Combination 2 calculation to find the size of the sub-structure and thento check that the strength of the resulting structural element (e.g. square padfooting, or cast-in-situ concrete pile) is satisfactory to carry the internal forces andmoments found using Combination 1. Obviously, where the structuralstrength of

the foundation is not in question, this second step will be unnecessary.

Which of the two Combinations will prove critical may not always be obvious. Inboth Examples 4.1 and 4.2, in which a square pad is subjected firstly to a verticalload and secondly to vertical and horizontal loads, Combination 2 proves to becritical to the dimensioning of the pad. However, an increase in the eccentricity ofloading as the horizontal, variable load increases relative to the vertical load wouldbe found to result in Combination 1 becoming critical.

For this reason, in principle, BOTH Combinations require checking, though adesigner will, with experience, know that calculation using only one Combination willsuffice for a straight-forward design problem.

Clause2.4.7.3.4.2(2)P

The manner in which DA-1 is used in STR and GEO ULS calculations is nowdescribed for simple foundation design problems. Also discussed are means ofsatisfying the SLS requirements.

4.3. Spread foundations

4.3.1. Overall StabilityBS EN 1997-1 requires a check of the overall stability of the ground mass bothbeneath and adjacent to the foundation itself. Figure 4.1 shows that the potentiallyunstable ground may contain the foundation (failure surface A-B) or may pass closeto it (C-D). Since failure along C-D may substantially affect the bearing capacity ofthe foundation, failure along C-D should be as sufficiently improbableas bearingfailure of the footing itself (see Section 5.2 for a discussion of slope stability).

clause 6.5.1

4.3.2. Design of the foundationThe Code requires either of two calculation methods to be adopted:

a) A direct method which involves two separate processes:- firstly, a ULS calculation using ground properties;- secondly, a settlement calculation to check the SLS requirements;

b) An indirectmethod in which a single calculation is based on comparableexperience (an essential prerequisite), and which uses the results of field or

clause 6.4(5)P


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46

ly mm h v SLS l. Thmh mplly v h ULS pv h h mpl xpvlv ml h h l xpl.

Figure 4.1 - Plly l lp pp f

U ll mh f ULS .Th fml ULS qm p y h qly

E R (2.5)

I h mpl ll F. 4.2,

E = V, h ULS l ml h f

R h f h f l ml .

V l h wh f h f f y kfll ml ( l ) pl .

Clause6.5.2.1(1)P

Rmy ll lyl m-mpl fml. Annex Df BSEN 1997-1 pv wly- fml f 58. Thpply f hm .

58

N hAnnex D fmv l p h Nl Ax; f, hNA BS EN 1997-1 xp mm h lv fml .

A C

B


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47

Figure 4.2Smpl p f l vlly .

UI Mh f m ULS SLS .A ypl , mpl mh wl h l f fl .Whl EN 1997-1 p pph pm mmly h UK (Annex Ef BS EN 1997-1), h, m mm mh l h l f h SPT CPT59.

clause 6.5.2.3

UULS - Ppv Mh clause 6.5.2.4

A h m, pm p p, f mplp f, f xmpl, Tl h Bl Rl. Th

p l m h SLS qm.

USLS SlmU clause 6.6

A h , BS EN 1997-1 y ll hw ll f mvm y ff mpl mh f llmm l lm. I l ff m lm pl lvl f l fm.

clause 6.6.2Annex F

Annex H

USl Smlly, BS EN 1997-1 y ll h m f h f mm f h BS EN f h lvl ml (.. BS EN 1992 f f ).

clause 6.8

I h fllw xmpl f h f BS EN 1997-1 f h f hllwf, Exmpl 4.1 ll hw h ll pfm f p f j vl, xl l, whl Exmpl 4.2 llh m f wh vl hzl xl l.

59

Rl fm h p (SPT) hv l h llwl p (m 25mm lm) f f ( Tml, 2001). Rlfm h p (CPT) hv mlly ( BRE, 2003).

FV

WW

RBdB

VBdB


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48

P

OPM EC7 8200M y/Exmpl 4.1SF 8/2004Chk/

PS 9/2004

Spread FoundationsP F Cly Sl

Vl L Oly

[w l]

;k, h wh y f l 20kN/m3

;k, h wh y f 24kN/m3

;k, h vl f h h 60kP

Bearing Resistance

Pp T m wh f f, B, h m h BR qm

RqVR

V vl f h vl l ()R vl f vl l ()

1.5

500kN

0.5

0.5

B

Cl6.5.2

6.5.2.1(1)Eq. 6.1.


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49

Pj Nm


PS 9/2004

1Tl Am 2m x 2m p f

Pm, vl h L ()

(1) Imp vl l lm 500kN

(2) Wh f F

W. f lm (1 0.5 0.5 24) 6kN

W. f f p (2 2 0.5 24) 48kN

W. f kfll ((2 2 1) (0.5 x 0.5 1)) 20 75kN

129kN

Tl Ch (l) Pm L

Vk= 629kN

Design Approach 1

Cmm Th ff h lv p

. Th m l pph h lyl

mh.

Analytical Method

U C

R/A = (+ 2) + q

N Smplf f h f vl l h

f p wh l.

Shp f

Sq f, = 1.2

A f f

P 2m 2m, A = 4m2

2.4.2(4) &6.5.2.1(3)

(1)

2.4.7.3.4.2

6.5.2.2Ax .3

Eq.1


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50

Pj Nm


PS 9/2004

B R

R = 4[(+ 2). 1.2+ q]

Combination 1 A1 +M1 +R1

L (A1)

V1 = Gx Vk

V1 = 1.35 629

V1 = 849kN

Sh (M1)

= k/

= 60/1.0

= 60kP

Sl Sh, vl j f (q) (A1)

q = qkG

= (1.5 20) 1.0

q = 30kP

B R (R1)

R1= Rk/RV

= Rk/1.0

R1= Rk

Fm Eq 2

R1 =4[(+2) 1.260+30]

R1 = 1601kN

Chk f V1R1

Fm Eq 3 Eq 7

849kN < 1601kNF 2m2m pl f

Apph 1, Cm 1

(2)

2.4.7.3.4.2

Tl A3(Pm

Ufvl)

(3)

Tl A4(U hh)

(4)

Tl A3(Pm

Fvl)

(5)

Tl A5(R1. B)

(6)

(7)


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51

P


PS 9/2004

Combination 2 A2 +M2 +R1

L (A2)

V2= 1.0 629

V2= 629

Sh (M2)

2= 60/1.4

2= 43kP

Sl Sh, Vl (A2)

q2= qkG

= (1.5 20) x 1.0

q2= 30kP

B R (R1)

R2= R/R;V

= R/1.0Fm Eq 2 v (Eq 9 & 10)

R2 = 4[(+ 2) x 1.2 43 + 30]

R2 = 1181kN

Chk f V2R2

Fm Eq 8 Eq 11

629 < 1181

F 2m2m pl f

Apph 1, Cm 2.

Cmm1. I pp h h p l m mll ll mply

wh h qm f , hwv h vly (pl lm)

2. N h Cm. 2 vy lhly m l h Cm. 1 R;2/ V;2(1.88) l h R;1/ V;1(1.9)

2.4.7.3.4.2

Table A3

(Permanent

Unfavourable

(8)

Tl A4(U hh)(9)

Tl A3(PmFvl)(10)

Tl A5(RI B)

(11)

6.6.2


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52

P


PS 9/2004

Settlement

Cmm F hfw w p p

h

() vlp f wh h f lm

ly, h fllw q

VkRk/3

() Uk lm ly h mm

l lm.

Settlement Option (a)

N Cl py ly

Fm Eq 1

Vk= 629kN

Fm Eq 6

B Cpy, R1 ffvly f

RV = 1.0 ( )G = 1.0 (h)

= 1.0 (h h)

Rk = R1

Rk = 1601kN

Chk

Rk/Vk= 1601/629 = 2.55 (


53/139


53

Pj Nm


PS 9/2004

W. f kfll 120kN

201kN

Rv Tl Ch (l) Pm L

Vk= 701kN

B R

Fm Eq 2

Rk= 2.5 2.5[(+ 2) 1.2 x 60 30)]

Rk =2501 kN

Chk, Eq.12

Rk/Vk = 2501/701 = 3.56 (>3)Cl U f 2.5m 2.5m wh

lm ly k.

N Th p l f h Rk/ Vk~3

Settlement Option (b)

Uk lm ly, p f 2m 2m.

(i) Adjusted elasticity method

Pm

ml, E = 12MN/m2

P R, = 0.2 (ff ly)

Cly ly (z) 10m hk lw h f h f.

Mh

N Th my h y l mh. Th xmpl

Bl F.G (1974). Hvly vl ly.

COSOS. Apl. Ph P.

Fml

Slm = I. q B / E

(Sml = p..f/Em)

Eq F.1

Bl F 4

Bl F 7


54/139


54

Page of 137Project Number

ODPM EC7 8200Made by/dateExample 4.1SF 8/2004Checked/date

PDS 9/2004

52

Butlers charts are used to determine settlement at the corner of a

footing

centre= 4 corner

where Bcorner=1/2Bcentre

From charts

For z/b = 10, L/B = 1, = 0.5

I = 0.37

For z/b = 10, L/B = 1, = 0.1I = 0.5

For = 0.2, by interpolation

I = 0.47

Settlement

From Eqn 14

corner= 0.47 (683/4) 1/12

= 6.7 mm

centre(settlement of pad)

= 4 6.7 = 27mm

Depth Correction Factor

As the footing is 1.5 m below ground level a depth correction factor isused. The engineer may choose any suitable method. The methodchosen for this example is:Fox E.N (1948). The mean elastic settlement of a uniformly loadedarea at a depth below the ground surface. Proc. 2ndI CSM.Rotterdam. Vol.1.p.129132.

D depth of footing = 1.5m

a width of footing = 2m

b length of footing = 2m

D/ab = 1.5/2 = 0.75

a/b = 1

D/ab = 1.5/2 = 0.75


55/139


55

P


PS 9/2004

H

O

Fm h

ph f, = 0.78

Slm =

= 0.78 27

Slm = 21mm.

N Ovll lm f f lv. Fqlyh f plm q h

ppl f fh f. Hwv f l h25mm f fl f vl f vll mvm.

P 2m 2m pl

(ii) Settlements caused by consolidation

Pm

Cff f vlm mply, Mv= 0.1 m2/MN

Cly ly 10 m hk.

Fml

Slm = Mv. p. h

p I vl f l ly

h Thk f h h l ly

H Ovll ph f l h f

Exm 5 ly, h 2m hk, lw h f.

Evl f vl h f h ly

U h J N., Bjm L. Kjl. B. (1956) Vl v

L v Fmppv.NGI Pl N. 16.N Th my h y h l mh.

Z = 1m

Z/B = 1/2 = 0.5 p / q = 0.7

Z/B = 3/2 = 1.5 p / q = 0.18

Z/B = 5/2 = 2.5 p / q = 0.07

Ax F.4


56/139


56

P


PS 9/2004

Z/B = 7/2 = 3.5 p / q = 0.04

Z/B = 9/2 = 4.5 p / q = 0.02

Cmm A h ll , h

ly ppxm ly h l l

ppl .. 500 kN

Slm

= 0.1 500/4 (0.7 + 0.18 + 0.07 + 0.04 + 0.02) 2

Slm = 25mm

Cmm. Cmmly p p p h ll

m lm h m f h mm

l lm f hvly vl ly ..

L Cly.

Apply h m l Op (.1)

P 2m 2m pl


57/139


57

P


PS 9/2004

Spread Foundations

P F Cly Sl

Vl Hzl L

[w l]

;k h wh y f l - 20kN/m3

;k h wh y f - 24kN/m3

;k h vl f h h - 60kP

Hk h vl hzl l - 75kN

N F ly h ll f z f 2.2m x 2.2m p. A 2m 2m f wk f l .

B R

Pm vl h l(1) Imp vl l lm 500kN(2) Wh f F

W. f lm (10.50.524) 6kN

W. f f p (2.22.20.524) 58kNW. f kfll ((2.22.2x1)-(0.50.5x1))20 92kN

156kNTl Ch L Vk = 656kN

1.5m

500kN

0.5m

0.5m

B

75kN

1.0m

Cl6.5.2

(1)


58/139


58

P


PS 9/2004

Appl L (A A1)

Vl LV1 = G VkV1 = 1.35 656

V1= 886 kN

Vl hzl l

H1

= Q

Hk

= 1.5 75H1= 112.5 kN

Mm H1

M1 = 112.5 2.5

M1= 282kNm

Cmmy Th mm l f h f.F ll f llwl py v f wh (B1) v h f f h ppl l. Th my h y l mh m B1. Th mh h fh xmpl Myhf G.G (1953). Th py f f l l. 3 ICSMFE. Zh. Vl.1p.440-445

Ey = 281/886 = 0.32

Effv wh

B11 = B 2 = 2.2 (2 0.32)

B11= 1.56m

Effv f f

A11 = 1.56 2.2 = 3.43 m2

Shp f

1 = 1 + 0.2(B/L)

Tl A3(PmUfvl)(2)

Tl A3(Vl

Ufvl)(3)

(4)

(5)

(6)

(7)


59/139


59

Project Number


PDS 9/2004

sc1 = 1 + 0.2 (1.56/2.2)

sc1= 1.14

Inclination factor

ic1 = 1/2

ic1= 0.84

Design bearing resistance

Using the analytical method as with example 1

R/A1

= ( + Z) cu . sc . ic + q

Note: Except for A1

, ic, and sc1 above the values used are as given in

Example 4.1 for Combination 1.

Rd1 = 3.43 [( + 2) 60 1.14 0.84 + 30]

Rd1= 1116 kN

Check Vdl RdlFrom Eqn (2) and (10)

886 < 1116

For Combination 1,

2.2m 2.2m footing has sufficient bearing resistance

Combination 2 A2 + M2 + R1

Applied loads (Action A2)

Vertical Design Load

Vd2 = G VkVd2 = 1.0 656

Vd2= 656kN

Horizontal Design Load

Page 57 of 137

D.3(1)

(8)

D.3(1)

(9)

6.5.2.2

Eqn D.1

(10)

Table A3

(PermanentUnfavourable)

(11)

1 + 1 112.5

3.43 x 60( )


60/139


60

Project Number


PDS 9/2004

Hd2 = 1.3 75 = 98 kN

Moment, due to Hd2

Md2 = 98 2.5 = 245 kN

Eccentricity

e = M/V = 245/656 = 0.37

Effective width

B12 = B 2e = 2.2 (20.37)B12 = 1.5m

Effective area of footing:

A12 = 1.5 2.2 = 3.3 m2

Inclination factor

ic2 = 1/2

ic2 = 0.78

Shape factor

Sc2 = 1 + 0.2(1.5/2.2) = 1.14

Design bearing resistance

Rd2= 3.3 [(5.14 43 1.14 0.78) + 30]Rd2 = 748 kN

Check Vd2 Rd2From Eqn (11) and (19)

656< 748

For both combination 1 and combination 2,

2.2 2.2 footing has sufficient bearing resistance

Comment:

Again, Comb. 2 is critical since Rd;2 / Vd;2 (1.14) is less than

Rd;1 / Vd;1 (1.23)

1 + 1 98

3.3 x 43( )

Page 58 of 137

(12)

(13)

(14)

(15)

(16)

D.3(1)

(17)

D.3(1)

(18)

(19)


61/139


61

P


PS 9/2004

Sliding Resistance

RqH R

R, f pp

R = A.

N A h ly f ppCm 2 vl .

A f mpv l

A = A2= 3.3 m2

Sh Rfm Exmpl 4.1, Eq. (9)

;= 2 = 43 kP

Sl R

R = 3.3 43= 142 kN

Chk H < R

Fm Eq (12)Appl Hzl L H2 = 98 kN

98 kN < 142 kN

Sl OKU 2.2m 2.2m p f

N A lm hk q ( Exmpl 4.1).

6.5.3

Eq 6.2

6.5.3.11(P)

Eq 6.4


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62

4.4. Piles

4.4.1 General

Section 7f BSEN 1997-1 f h m mphv. M f v vl pl j vl l1.

Th w groundresistance2 hh Section 7. I h x fpl, hy m py(whh mp ).

Th C l hvly w pl l 3, wh h mp h h pl ll wh hp BSEN x ( S 6).

I l p fm mm p, h C h fl f, , f v h h py f plfm pl l fm pfl4f h l Bx 4.2.

clause 7.1(1)Pclause 7.6

clause 7.4.1

clause7.6.2.2(8)P

BOX 4.2Cl f

Cl f hv fm m Ep p whh pl h l f l vl pfl f, f xmpl, CPT. Th f mk llw f h qy f kw plpfm h , f h vly f h . Th, h m vll h lw h l f vl, l mll pl, whl hm vl h h m pm h vl; h l ffm y m . Sm k fm h vl f h

f pv Annex Af BSEN 1997-1 f B (2001).

Lm .A l pv f h m mm lm f plf. Th f v f h h l ULS fl m, hhl l; h l mply h ll hxpl hk hl m f ll f hm.

Clause 7.2(1)P

1Th S ppl ll pl, l f h ll mh (v, jk, w

wh wh ) h xp hv (y - y f),whh f y ff pl f vl.2

Th w hly h h fl xm fl h .Th w mph h h m m h mxmm fm h (mxmm hf f , f pl mp, y ).3Th E k f pl ( ) m

h vm fl x mh h ppy vl fm v pl ll p h my lk h q x qly.4I h x f BSEN 1997-1, pflmy hh f vl q f fm,

fm f q mxmm ph, h m h h lw S P T.


63/139


63

A.I h ly m S 2 f h G, BSEN1997-1 f h pf pl h l fm mvm1.

Design methods and design considerations

BSEN 1997-1 q h pl f h fllw (hl h Ah)

- h l f relevantpl l ;- ll h based on valid load tests2

- h l f ym ( vl l );- v f h pfm f mpl pl.

Gv h mph pl l , BSEN 1997-1 h q y h ym pl l .

O f h ULS qm h fl hpp p fm plm f h f. I hm, mm p ll pl plm,h C q h f lm p3.

clause 7.3.2.1

clause 7.4.1

clause 7.5

Cmpv l fl f the state in which thepile foundation displaces significantly downwards or upwards with negligible

increase or decrease of resistance . l f pl mp f ffl h h , fm pl f l vlm. I mm wh mh p, BSEN 1997-1 hf

clause7.6.1.1(2)

1A fm- vl lm w ( v hf f);

- pw plm hv f h pl;- hzl plm vly l h pl.

Vertical settlements causing downdrag:Ap h mxmm (l-m) w l f h l vy vv v l pl z ( clause 7.3.2.2), plwh h lm f h mll / h mpl ly vy hk. T vh, fl l-pl ly my , f whh hl plhl l.Heave: F hv, BSEN 1997 - P 1 q h pw mvm ly ( clause 7.3.2.3(1)P); , hl pl hl l.Transverse loading: My , h pl m, wh mvm j pl v l. Th lv l h C ( clauses 7.3.2.4(2) 7.3.2.4(3)) whh mm l-pl

ly, h m l -l pp, h hzl ml f- p-y v.2Sh ll wl h wll-kw mh whh h hf f pl

ly l pp () f h h . Vl f w 0.3 0.9 (p h yp f ly h m whh h m) based on the back-analysis of pile tests in comparable situations.3I hl h fh v Section 7f h E hw

hk plm p ULS h pp . Th v fp f S 4.3.2 h G l lv f pl lm.


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f fl pl h lm f 10% f h ffv m1. clause7.6.1.1(3).

f pl xh mpv All lm lm f xlly-l, vl pl p f vlpl v f h fllw qly f

F; R; (7.1)wh

F; h vl f h xl mpv l;

R; h vl f h lm mpv .

R, m fmpl l ;- l;- ym pl l .

clause7.6.2.1(1)P

clause 7.6.2.2

clause 7.6.2.3

clauses 7.6.2.4to 7.6.2.7

A h mpl BSEN 1997-1 , f h-f-h-mll pj pl, mphv pl lypfm, h G f, S 4.4.2, h h pl l 2. Th C qm f pll hv mm Appx 9.6.

4.4.2 Calculating ultimate compressive resistance using ground parametersfrom tests

Ay ll h l p pl py mhv established from pile load tests and from comparable experience.

Ay y h ll mh my l wh y

ml f ffly fl. Nh m hf BSEN 1997-1.

clause7.6.2.3(1)P

clause

7.6.2.3(2)

1Th p f wll-kw f f fl mp, h

ll mh fl l m l , hl vy fly p h h fl .2I hl mm h mh , h -mh f xmpl,

l wh pl l.


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Tw ll mh v

- A lv p, wh h l (.. hh, , ) f ll lv l fm, ll h lv fm, h

characteristic values of base resistance and shaft friction in the variousstrata1; h mm mh f h UK.

- A p whh ll, f h pfll, h l fm m pfl f l2.

clause7.6.2.3(8)P

clause7.6.2.3(5)P

Alv pTh h vl Rb;k Rs;kmy ll ly fm vl f pm h hv ppl v , wh f pfl vll, h

R;k= Aq;k

R;k= As;i qs;k;j (7.9)wh q;k q;k; h vl f hf f fm h vl f pm m . Thm l wy f ll h pl mpv fm lm l h fllw p 3 & 4, hw lw f wh pfl f .

clause7.6.2.3(8)

P

I h lv p, f explicitly f vly. Cqly, h vl f q;k q;k;hl mplly k

f- h vly f h ,- h vlm f l vlv h fl mhm ,- h pl vly f h pl ,- h vly h ff f pl ll - h ff f h .

A h vl f h pl f , Tl 4.1 w vlp fppl BSEN 1997-1 wh h -f, hy hmlvffly l l h lv p lml f q. Exmpl 4.3 p vl f 1.4 f h ml f m wh vl wll q y h Nl Ax.

1Ay h qly f f wkmhp h pl p

my fl h h f h vl.2Th p ml h h l f pl l , h y

f f vly w h l f h ff pfl f .

i


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U pfl f .Th p h p

1. Cll h mpv pl , R;l, ply f h pflf fm

R;l= R;l + R;l

wh R;l R;l h ll hf pvly. Th l h p f pl f w hl f h pfl f .

clause

7.6.2.3(5)P

2. Cll h h vl fm

R;k= (R;k+ R;k) =

wh R;l h ll mpv , R;l hll mpv hf wh 3 4 lf h p h m f pfl f , , ppl pvly - h m vl (R;l )m = (R;l + R;l )m = (R;l)m+ (R;l)m

- h lw vl (R;l )m = (R;l + R;l)m.

Vl f 3 4 v Table A.10fAnnex Af BSEN 1997-1 p Tl 4.2 lw f v.

fon = 1 2 3 4 5 7 10

3(m) 1.4 1.35 1.33 1.31 1.29 1.27 1.25

4(m.) 1.4 1.27 1.23 1.2 1.15 1.12 1.08

Table 4.2 - Vl f l f f l( m f pfl f )

A f h p pl l l ( Appx 9.6), h pf ll h h vl f h pl mpv hmmm f h w (ffly f) lw m vl pv ly vv l h k f () h m fpfl f mm h v () h f h l w pfl l1.

1N h, f BFB h 1.0, h vl f h x h vl

, f BMB h 1.0, h vl f h ml ppy wll l h hh vl.

Rb;cal+ Rs;cal=

Rc;cal= Min

(Rc;cal) mean ; (Rc;cal) m

3 4{ }


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3. Th h y pply h pl f h

l h R;k y pply h pl f pvly h h hf fl hh , h

R;= R;k/

R;= R;k/+ R;k/

Tables A.6A.8fAnnex A BSEN 1997-1 l h vl f h f;f v, hy hv w h Tl 4.1.

clauses7.6.2.2(14)P

and7.6.2.3(4)P

4. A my k f h ly f h h pl f l fm wk pl pl. If h l , h vl f 3 4 my v y 1.1 pv 3 flllw 1.0.

clause7.6.2.3(7)

BSEN 1997-1 l l ml f pl h y h p fh mpl G. Cqly, f h fllw ml h l h App F

ll f lm mpv h l f ympl (Appx 9.7);

h f pl (Appx 9.8);

h f vly-l pl1.

U A-1 f pl mpW hv h, l, A-1 q h w Cm ppl

ply

Cm 1 A1 + M1 + R1

Cm 2 A2 + M2 + R1

1A wh xlly l pl, h fllw pply

h lm p hl hk f h l f h, ff pl, h f l, l pl, f fl f h pl yl f h l f ( clauses7.7.1.(2)P 7.7.1(3));

f y p ff ( clause7.7.1(4)P); m h v pl l l ( clause7.7.2)

l pl h pm ( clause7.7.3); hk f fl f h pl lf; h v pl plm.

Spf qm h vly f h h f ( clause7.7.2(3)P) h pl h fxy wh h ( clauses7.7.2(4) 7.7.3(4)P).Th f m hy wh hzl ml f xplly BSEN 1997-1 f ly h hv f l, l pl ( clause7.7.3(3)).


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h, h hl mlly ll f vl f ml pp (h), f (R1) h lly ppl.

Hwv, h f pl ( h) ff fm h mh f pl h v fm h l f mm l .

F pl, Cm 2 hf m

A2 +(M1 M2) +R4

Th m h, f pl mp, M1 (M= 1.0) h f

f R4 (R> 1.0) ppl ll hvl f pp h vl f l mm. I pf f pl j fvl fmh (.. w ll h p), f vl M2 (M1.0) ppl h pp ll h vl f hfvl , whl R4 f vl ll h vlf h (fvl) w xl l.

.4.3 Vertical displacements of pile foundations (serviceability of supportedstructure)

A f my h f, y h lm f pl pv h lm vly lm x hpp 1.

I h m f h m wll ly ppxm f ll h p lm2. A, BSEN 1997-1 pmlm ll pl y py ll wh hhf f fy h a sufficiently low fraction of the ground strength ismobilised; hwv, v h hh f vl v h C.

Exmpl 4.3 4.4 ll p f h f h mpv f pl BSEN 1997-1.

clause7.6.4.1(1)P

clause 2.4.8(4)

1Th vl f llwl mvm h hl l h . Sm

v lm vl f l fm v Annex Hf BSEN 1997-1. Fh my f Bl l (1977).2Mh f ll h plm f pl f l h wll kw l l

pph f Pl v (1980), wll f lm ll mh h ml f hf f.


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P


PS 12/2005

Pile DesignCfa pile in clay

[w l]

Pp f ll T m h lh f pl q.

Design Approach 1. (Axially loaded piles)

Combination 1: A1 + M1 + R1

A (L) (A1)

Pl F, G = 1.35

F; 1 = 1500 1.35

F1 = 2025kN

N F py h ll y ff h whf h pl h pl v l l.

Cl

2.4.7.3.4.2 (2)

Tl A3(PmUfvl)

(1)

1500 kN

600mmm

;k= 20 kN/m3

;k= 60 + 8z kP

(Chpfl)


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P


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B Pl R F

Pl B 9

Pl Shf F h , p = 0.5

Pl Shf 0.5

Ml F (M1)

= 1.0

S = ;k

N N mf p l pm q f h f xlly l pl.

R (R1)

B R R= 9.;A

Shf R= 0.5.;A

Cmpv R, R;= R;+ R;

Pl f f Cf pl

= 1.1

= 1.0

N Wh v h vl f pl fm pm pl f hv y Ml F.Pm Ml F = 1.4

Pl f f pl f CFA pl

;= 1.1 1.4 = 1.54

; = 1.0 1.4 = 1.4

Op (1)

B R R;= (9/1.54) C.A= 5.85 C.A

Skmp (195B/L = 1, /B>5

Tl A.4U ShSh

(2)

(3)

7.6.2.3(3)

Tl A.8

7.6.2.3 (8)

(4)

(5)

(6)


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Shf R R;= (0.5/1.4) C.A= 0.36 C.A

N C h v h h f h ly l hpl hf.

Cmpv R, R; = R; + R;

m f lh f pl y p l [ Eq (9)]

Ty 19m l pl

R;1 = 5.84 (60 + 19 8) (0.6)2

4+ 0.36 60 + (60 + 19 8) (19 0.6)

2= 350 kN + 1753 kN

R;1 = 2153 kN

Fm Eq (1) F;1= 2025kN

R;1> F;1

ClA pl 19m l, 600mm m y h l f 1500 kN Cm 1.

(7)

(8)

(9)


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Combination 2: A2 +(M1 or M2) +R4

A (A2)

Pl F, G = 1.0

F;2 = 1500 1.0

F;2 = 1500

Ml F (M1) f Cm 1 Cm 2 h

m .. M1, h.

R (R4)

Pl f f Cf pl

= 1.45

= 1.3

Pm Ml F = 1.4

Pl f f pl

;= 1.45 1.4 = 2.03

; = 1.3 1.4 = 1.82

Ty 19m l pl

R;2 = (9/2.03) .A = 4.43 .A

= 4.43 (60 + 19 8) (0.6)2

4= 266 kN

R;2 = (0.5/1.82) .A= 0.27 .A

= 0.27 60 + (60 + 19 _ 8) 19 0.6

2= 1315 kN

R;2 = 266 + 1315

(13)

2.4.7.36.4.2(2)

Tl A3(PmUfvl)

(10)

7.6.2.3 (4)Tl A8

7.6.2.3 (8)

(11)

(12)

(14)


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= 1581 kN

Fm Eq (10) F;2=1500kN

R;zF;z

Cl(1) A pl 19 m l, 600mm m y h l f 1500

kN Cm 1 2.

(2) Cm 2 mlly l ( R;2/ F;2 ) [1.05] A2. Lateral Earth Load Moment(105.5) (100.5)

A1. Lateral Water Load Moment > A2. Lateral Water Load Moment(17.8) (13.13)

Conclusion(1) Wall Base of 2.7m is acceptable

(2) Combination 1 governs overturning

Sliding

Require: HdRd

Establish design resistance to sliding by factoring Ground PropertiesCombination 2 (Factored Ground Properties)

(17)


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Project Number


PDS 9/2004

Lateral Load, Hd2 = Hd2s+Ud2s= 63.5 + 19.6 = 83.1kN/m run

Design Resistance to Sliding by Factoring Ground Properties

Rd2= Vd2tan d2

Vd2= [Effective Wall Load] + [Wall Shear] = [140.3] + [14.8]Vdi = 155.1kN/mrun

Basal angle of shearing resistance:

tan dB2= tan d2tan d2= 0.5 (Eg 2b p5)Rd2= 155.1 0.5 = 77.6 kN/m run

Check if Hd2< Rd2

From Eqn (19) and (20) (83.1 >77.6)

So, Wall Base of 2.7m is not acceptable for sliding

Try gravity wall with 3.2m wide base

Vd2= 48 + (2.7 0.5 24) + (3.5 2.7)/2 24) (19.6 3.2)/2 + 14.8

Vd2= 177.2 kN

Rd2= 177.2 0.5 = 88.6 kN

Check: Hd2s


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