lecture 7 - example 2.3 (van seters)

Evaluation of Eurocode 7Example 2.3 PILE IN CLAYpETC 10

Adriaan van SetersFugro Ingenieursbureau BV

The Netherlands

2nd International Workshop on Evaluation of Eurocode 7, Pavia, Italy, April 2010

Introduction in example Introduction in example SLS-design source of parameters Characteristic values of Cu profile Characteristic values of Cu profile SLS required pile length ULS shaft friction / endbearing computationULS shaft friction / endbearing computation Design Approaches used Load/strength/resistance factorsLoad/strength/resistance factors ULS computed pile length Conclusions


Pile in Clay Outline of problemPile in Clay Outline of problem

W TW.T.

Soil data: boreholes 13,14SPTs borings 11, 12, 14 -17CPTPressuremeter tests PM2, PM3Triaxial UU borings 11, 12, 14 -17


Soil Conditions0 3 to 4 m Man made ground, clayey sand, gravelBelow 3 to 4 m London CLAY Cu: 30 230 kPaBelow 34 m SAND

2nd International Workshop on Evaluation of Eurocode 7, Pavia, Italy, April 20102nd International Workshop on Evaluation of Eurocode 7, Pavia, Italy, April 2010

All data - design profileg p


Questions asked

1st Question 17 Respondents from D UK PT PL IT:

Questions asked

1 Question 17 Respondents from D, UK, PT, PL, IT: Permanent load 300 kN, variable load 150 kN

downwarddo a d SLS maximum settlement 20 mm SLS-State required pile length?q p g ULS-State required pile length?

2nd Question 7 Respondents: Repeat the exercise using the given Cu design

values (red lines)


General Results

Observations:

General Results

Observations: 13 (of 17) have designed more than 3 piles in clay 15 (of 17) are confident in a sound EC7 design 15 (of 17) are confident in a sound EC7 design 9 used an average of all tests 8 used nearest test results, took location into8 used nearest test results, took location into

account 13 (of 14) assumed a linear/bilinear/stepped pp

variation of Cu or E with depth


Parameters used for SLS-designg

10

12

6

8

10

2

4

6

0

2

Qc-CPT SPT-N UU-Cu Plim Eund E'drain PoissonNu

M th ibl !More than one answer was possible!


Relation E d and OCR Duncan et al Relation Eund and OCR, Duncan et al Cu = 4.5 N SPT, Stroud Adhesion factors Tomlinson Adhesion factors, Tomlinson DIN 1054 Correlations UU and qc, KempfertCorrelations UU and qc, Kempfert Transform functions for bored piles, Gwizdala et al EA PfahleEA Pfahle Correlation Cu and Plasticity Index, Duncan et al. Relation E/N60 (SPT), Stroud/ ( ),


Answer No Comments

By eye 9

Linear regression 3

Existing standard 2 DIN 1054, EN1997-1

bl h d l dPublished correlation 2 CIRIA, SPT-Stroud

Other 5Other 5


Characteristic values for SPT N CPT Pli d T i i l C

Questions 11- 13 (qc Plim SPT-N) not answered

SPT-N, CPT-qc, Plim and Triaxial CuQuestions 11 13 (qc, Plim, SPT N) not answered Only characteristic values CU-value (Q14)

Each participant converted test result back to

Cu - Triaxial versus depth

15

20

O

D

]

Not many

esu t bac toCu-value

5

10

15

v

a

t

i

o

n

[

m

O

ydifferences between countriesVariation /: 0,2

-5

0

0 50 100 150 200 250 300

E

l

e

v

Cu - value [kPa]

Average Average - st dev Average + st dev


Method of calculation Pile settlement

No method from the national Annex (Annex F is N A )

Method of calculation Pile settlement

No method from the national Annex (Annex F is N.A.) German standard DIN 1054, Annex B EA-Pfahle German method EA Pfahle, German method Wide range of handbooks, references:

Linear elastic solution T-z, q-z curves, Fellenius Transform functions method T-z curves Reese & Wang (1990)T z curves Reese & Wang (1990) Poulos and Davis (1980) Randolph and Clancy (1993) Piglet Randolph Piglet, Randolph Tomlinson


Q17 Which length is needed in SLS state?

12 Answers received

Q17 Which length is needed in SLS state?

12 Answers received

Average pile length is 14 m Average pile length is 14 m

Standard deviation of 2.8 m variation 20 %Standard deviation of 2.8 m variation 20 %

All countries in the same rangeAll countries in the same range


Tests used for ULS Pile design

Tests used for ULS Pile design

16

12

14

16n

t

s

8

10

p

a

r

t

i

c

i

p

a

n

2

4

6

N

o

o

f

p

0

2

Qc-CPT SPT-N UU-Cu Plim

Soil tests


Correlations for ULS designCorrelations for ULS design

Wide range of correlations: DIN 1054 Cu = 4 5 N (SPT) or f1 * N (SPT) Stroud Cu = 4.5 N (SPT) or f1 N (SPT), Stroud Tomlinson, adhesion factor a for piles Kempfert et al, Correlation from UU-test to cone resistance

P li h ili d PN B 02482 Polish piling code PN-B-02482 German code EA-Pfahle Cone qc = Cu * Nc + v0 CPT cu correlation Meigh (1987, CIRIA) DIN 4094-1: 2002-06 (CPT) Baguelin et al 1978 (pressuremeter) Baguelin et al, 1978 (pressuremeter)


Characteristic values of Unit Shaft Resistance

Characteristic values of Unit Shaft Resistance20

15

O

D

] Q_shaft,k at 7 m OD

5

10

a

t

i

o

n

[

m

O Countries:

D, I, PL, PT 55 kPa

0

5

E

e

l

e

v

a

UK 80 kPa

-50 50 100 150 200

Sh ft f i ti [kP ]Shaft friction [kPa]

Average qs qshaft + s qshaft - s


20

15

D

]

Q_base,k at -3 m OD

5

10

v

a

t

i

o

n

[

m

O

D

Countries:

D, I, PL, PT 1750 kPa

0

E

l

e

v

UK 700 kPa

-50 500 1000 1500 2000 2500

Unit End Bearing [kPa]

(UK applies a model factor of 1.4 in achieving at characteristic values)

Average qb qbase + s qbase - s

characteristic values)


Use of Design Approaches

Use of Design ApproachesDesign Approaches - ULS Design

10

12

a

n

t

s

6

8

10

o

f

p

a

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c

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p

0

2

4

N

u

m

b

e

r

o

DA1 - C1.1 + C1.2 DA1 - C1.1 DA1 - C1.2 DA2/DA2* DA3

Design approaches GermanyOthers


Use of Partial Safety Factors in ULS-checkLoad factors All participants: DA1 - Comb. 1, DA2 G = 1.35 Q = 1.5All participants: DA1 Comb. 1, DA2 G 1.35 Q 1.5

DA1 Comb. 2 G = 1.0 Q = 1.3

Partial factors on strength Generally no partial factors on Cu (DA3) were applied

Partial factors on shaft/base friction acc Nat Annexes: Partial factors on shaft/base friction acc Nat Annexes: DA1 - Comb. 1 shaft = 1.0 base = 1.0 (PL/PT: 1.25) DA1 - Comb. 2 shaft = 1.3/1.45/1.6 base = 1.6/1.7/2.0 DA2 shaft = 1.1/1.4 base = 1.1/1.4 -factors: 4 (9x) 1.135 to 1.7, 3 (2x) 1.45

Partial model factor UK / PT partial model factor of 1.4 / 1.5 on Cu


Results of the Analyses ULS Pile length

16 answers received

Results of the Analyses ULS Pile length

16 answers received

Average pile length is 15 1 m (SLS 14 0 m) Average pile length is 15.1 m (SLS 14.0 m)

Standard deviation of 2.7 m (SLS 2.8 m)Standard deviation of 2.7 m (SLS 2.8 m)

UK pile length 12.5 mUK pile length 12.5 m Italy pile length 17.5 m Others pile length ca. 15 mp g


17 participants from 5 countries!All l d il d C l i All answers translated soil data to Cu-value using many correlations!Variation of Characteristic values of Cu (no anomalies Variation of Characteristic values of Cu (no anomalies, below level + 7 m) within 10 %.

Many SLS-methods less ULS-methods (all based on Cu) Many SLS methods, less ULS methods (all based on Cu) Good agreement load factors + Design load (630 kN) Spread in h ft and b in DA1- Comb 2 (and DA2?)Spread in shaft and base in DA1 Comb 2 (and DA2?) Use of partial model factor? Variation computed pile length (SLS and ULS) ca. 20 %Variation computed pile length (SLS and ULS) ca. 20 %

Thanks for all contributions!Thanks for all contributions!


Is EC7 - Design Conservative? Comparison EC7 with previous designg

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Very

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Very

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More conservative About the same Less conservative


lecture 7 - example 2.3 (van seters)

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