Pile Design and Pile Load Tests in The NetherlandsAdriaan van Seters

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Contents

• Safety of pile foundations• CUR-committee 229 – Van Tol• Investigations 2011 – 2014• Standard comittee 2014

• Pile load tests• Static• Rapid Load test

• Discussion

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CUR 229 – Axial pile bearing capacity - 2010

Purpose of committee:• Determine pile factors p en s

• Evaluation of pile load tests• (new calculation model with Belgium and France)

Actually:• No damage in The Netherlands• Only sufficient tests for precast concrete and closed ended steel pipe piles• Other piles no evaluation

Problem:• Conclusions valid for other piles?• Many new pile types, too little tests• “My looks like a … pile” Same pile factors?

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CUR 229 – Axial bearing capacity - 2010• Displacement piles• Evaluation of pile tip in sand (norm p = 1,0)

• Evaluation of shaft friction - s in sand (norm s = 0,01)

Investigation University Western Australia• 28 pile tests• p = 0,834, variation coefficient = 0,32

Pile tip indeep sand

layer[* diameter]

No of tests Averagep - value

VariationCoëfficiënt

0 – 8 8 0,99 0,28

8 - 22 7 0,63 0,14

No of tests Averages – value

Variationcoëfficiënt

10 0,0099 0,36

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CUR 229 – Conclusion

International Investigations: In NL Pile TIP bearing capacity is overestimated

Van Tol (2015)

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CUR 229 – Conclusions

Conclusies CUR 229 for precast concrete and closed ended steel piles:• Calculation model shaft (s = 0,01) is OK• Shallow founded piles (< 8D in sand layer): Calculation pile bearing capacity

is OK (p = 1,0)• Deep founded piles (> 8D in sand): Calculation model is not OK

p tussen 0,6 en 0,7

Conclusie CUR 229 – other pile types (o.a. Vibro)• Too less tests, no conclusion

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CUR-committee C193

Purpose CUR-committee:• Why is there no damage at the moment Hidden safety?• How to deal with -factors• What happens for other pile types?• How to facilitate pile testing?

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CUR193 – Literature investigation – Hidden Safety

Number of aspects from literature (Deltares, Fugro, R’dam, 2013):1. Increase of bearing capacity in time – ageing

2. Remaining stresses in the pileafter driving – Effects on the pile loadtests? Underestimating pile tip bearing, Overestimating friction?

3. Limit values of cone resistance too low?

4. Pile group effects – densification?

5. Influence positive shaft friction – base effect

6. Influence of reaction piles on the pile load tests

7. Windload: does act completely on the foundation?

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CUR193 - Ageing

Axelsson (2012), Karlsrud (2014), Gavin (2015)

Only displacement piles.1. Increase of horizontal stress2. Increase of dilatantie3. Higher stiffness of the sand by ageing

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CUR193 - AgeingToename schachtwrijving in de tijd

0%

20%

40%

60%

80%

100%

120%

140%

160%

180%

1 10 100 1000

tijd (dagen)

Toen

ame

A = 0,1A = 0,2

Tijdstip gebouwgereed; t=300dagen

Tijdstip paaltest;t = 30 dagen

Increase of friction in sand - factor s – by ageing (logarithmic process?)

Pile test at 30 days after installing the pile

Pile load at 300 days after installing the pile

Increase 10 – 15 %

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CUR193 – Limitation of cone resistance too low?

In teh calculation model for pile bearing in sand LIMIT on qc

NEN-standard:Limit on pile tip resistance: 15 MPaLimit on shaft friction: 120 kPa á 150 kPa

Literature:Limit on pile tip resistance around15 MPa (some 16 MPa)Shaft friction just above pile tip sometimes 300 á 600 kPa

Conclusion:Pile tip bearing capacity limit: seems OKShaft friction: present limit is at the low side

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CUR193 – Pile groups - effects of densification

• Displacement piles in sand:• Increase of cone resistance in a dense pile group f1 x qc• For a 9-piles groep:

• For pile group at 3D distance f1 = 2,3• For row of piles 3D distance f1 = 1,3

verdringingspercentage

1,00

1,50

2,00

2,50

3,00

3,0 3,5 4,0 4,5 5,0 5,5 6,0

s/Deq [-]

f1 [-

]

e0 = 0,4 e0 = 0,6 e0 = 0,8

delta (e) = 0,4

8,7 6,4 4,9 3,9 3,1 2,6 2,2

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CUR193 – Pile groups - effects of densification

Oosterdokseiland – Amsterdam (2004)

16 18 20 22 24 26 28 30Conusweerstand,q c [MPa]

.0 .1 .2 .3 .4 .5Wrijvingsweerstand,f s [MPa]

0246810Wrijvingsgetal,R f [%]

a

Opdr. 1004-0044-001Sond. DKM EX2

AANVULLEND ONDERZOEK KAVEL 3 - 5 OOSTERDOKSEILANDAMSTERDAM

Sondering volgens norm NEN 5140: klasse 2conustype cylindrisch elektrisch a afwijking van de vertikaal

Opg. : PLD/GFR d.d. 02-Sep-2004

Get. : KGR d.d. 06-sep-2004

conus : F7.5CKE/B X = 122442.828

Y = 487726.276

SONDERING MET PLAATSELIJKE KLEEFMETING

MV = NAP m-6.33

35 37 38 36

37 37

30

35

31

-30

-29

-28-27

-26

-25

-24

-23

-22

-21

-20

-19

-18-17

-16

-15

-14

-13

-12-11

-10

-9

-8

-7

-6

-5

Die

pte

t.o.v

. NA

P [m

]

0 2 4 6 8 10 12 14

01

1

2

2

2

3

-30

-29

-28-27

-26

-25

-24

-23

-22

-21

-20

-19

-18-17

-16

-15

-14

-13

-12-11

-10

-9

-8

-7

-6

-5

Die

pte

t.o.v

. NA

P [m

]

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30Conusweerstand,q c [MPa]

.0 .1 .2 .3 .4 .5Wrijvingsweerstand,f s [MPa]

0246810Wrijvingsgetal,R f [%]

a

38 47 59 62 65 67 66 67 72 73 68 52

46 46 36 34

38

37 34 37 44 43 34 36 36 32

30

34

31

35 34 36 34

00

0

0

0

0

0

SONDERING MET PLAATSELIJKE KLEEFMETINGAANVULLEND ONDERZOEK KAVEL 3 - 5 OOSTERDOKSEILAND

PLD/GFR

AMSTERDAM

Get. :

Opg. :

KGR 06-sep-2004

02-Sep-2004d.d.

d.d.

Sond.Opdr.

a afwijking van de vertikaalconustype cylindrisch elektrischSondering volgens norm NEN 5140: klasse 2

-6.00

F7.5CKE/B

MV = NAP

conus :

m 487726.653

122419.535

Y =

X =

DKM EX31004-0044-001

Palen 450 mm

Distance 4 D 1,8 m

Increase coneresistance afterdrivinga :

f1 = 1,5 a 2!

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CUR193 – Pile groups - effects of densification

Result:• Factor f1 can go up to 1,5 á 2• Limit of cone resistance is 15 MPa• So limited effect???

In practice :• Increase bearing capacity by group effect: approx. 10 %

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CUR193 – Windloading – safety at load side?

Due to wind loading piles get a axial compression load piles displace vertically Reduction of neg shaft friction

Example calculationTotal load = 1000 (permanent) + 600 (neg shaft) + 600 (wind) = 2200 kNInteraction-calculation: Actual load is 1900 kNPossibly: 50 % of wind load taken by neg shaft friction

If no negative shaft friction- Full wind load on the piles!

Note:- Wind load is significant when highrise > 40 m.

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Decision Standards committee 2015

• Reduction of tip resistance p with 30 %• Values for shaft s remain unchanged• Stimulate pile load tests

- New value p maybe too low for other piles- Prove the present pile factors (from 1950 – 1980)

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Static Pile load tests

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NPR - standard

STATIC LOAD TESTS – 4 CLASSES:

A B C D

Ffailure Ffailure 120% Fd 100% Fd

SeparatemeasurementTip andshaft

Measurementonly atpile head

Measurementonly atpile head

Measurementonly atpile head

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RAPID LOAD TEST / STATNAMIC

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RAPID LOAD TEST – Statnamic/Statrapid

Statnamic:• Explosives• Gravel container?

Statrapid:• Block falls from determined heigth• Springs between block and pile

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RAPID LOAD TEST / STATNAMIC

• Procedure – Unloading Point Method• Alternative for Class B en D Pile load tests• 3 tests per pile (class B – investigation tests)• Failure load and load-displacement diagram• 1 test per pile (classe D – Control tests)• Only for piles in sand

• Piles in clay together with static test• (Take friction in upper soft layers into account)

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Results Rapid Load Test

Unloading Point Method

• Load depends of dynamic effects• Dynamisch effect = 0,

when velocity = 0

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Resultaat Rapid Load Test – Load - displacement

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Discussion

CUR 229 – 2010 - Pile load tests show lower safety than expected

No damage Hidden safety???• Ageing• Densification - Group effects• Other?

Feasibility of Pile load tests:• Static Pile load tests not going to failure (120 % Fdesign)• Rapid Load Tests

Thank you for your attentiona.vanseters@fugro.com

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Planning – NEN9997-1/NPR

NEN9997-1/EN1997-11 juli 2016 – norm gereedAanwijzing door Bouwbesluit per 1/1/2017

NPR – PROEFBELASTINGEN2016 - “groen” ter commentaarEind 2016 – Richtlijn gereed

a.vanseters@fugro.com

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Besluit Normcommissie 2011

NEN-COMMISSIE• Beeld is niet compleet (alleen geheide palen in CUR 229)• Schade gevallen niet bekend (verborgen veiligheid)• Alleen geheide palen marktverstoring• Veel “nieuwe paalsystemen” zonder proefbelastingen

BESLUIT• Paalklassefactoren p, s, en t ongewijzigd t.o.v. NEN 6743• Maximale geldigheidsduur tot 1/1/2016• Binnen 5 jaar nieuwe p, s, en t uit proefbelastingen• -factoren + beschrijving van paalsysteem deponeren bij NEN• Indien geen proeven reductie -factoren per 1/1/2016 met 33 %

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AFGELOPEN 5 JAAR• Onderzoek naar verborgen

veiligheid (CUR 193)– Literatuurstudie– Pilot groepswerking en ageing

uitgevoerd in centrifuge– Resultaat: Mogelijk hogere schachtwrijving door “ageing”

(tijdseffecten) en groepswerking bij geheide palen

• Geen middelen voor prototype testen• Geen geld voor verder onderzoek• Geen proefbelastingen beschikbaar gekomen

Periode 2011 - 2016

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Gevolgen voor Praktijk na 1/1/17

NIEUWBOUW• Lagere p

• Zwaardere en/of langere palen• Proefbelasten hogere p?

BESTAANDE BOUW NEN8707-ontwerp• Bestaande situatie huidige factoren• Belastingsverhoging bij Verbouw

nieuwe factoren

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Meer proefbelasten

NIEUWE NORM (TABEL 7C, VOETNOOT A) ONDERSCHEIDT:

• Projectgebonden proefbelastingen• Algemeen geldige proefbelastingen:

– Instrumentatie – scheiding tussen punt en schacht– Minimaal 2 terreinen– Beschrijving van het paalsysteem en installatieproces– Paalklassefactoren αp, αs of αt voor specifieke beproefde

paalsysteem van de betreffende leverancier

NPR - PROEFBELASTINGEN

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NPR-proefbelastingen

STATISCH PROEFBELASTEN – 4 KLASSEN

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NPR -factoren - discussie

REGISTRATIE VAN -FACTOREN

• Aanmelding belastingsproef bij NEN metbeschrijving paalsysteem en paalinstallatie

• (Aparte) NEN-commissie beoordeelt draaiboek• Proef wordt uitgevoerd met onafhankelijk toezicht• Rapportage wordt door NEN-commissie beoordeeld• -factoren en beschrijving worden bij NEN vastgelegd• -factoren alleen geldig voor betreffende leverancier