IE-NET cursus. Uitvoeringsaspecten bij paalfunderingen

(1)

Uitvoeringsaspecten bij paalfunderingen

17 november 2021, Antwerpen

ir Noël Huybrechts, Afdeling Geotechniek, WTCB & KU Leuven ir Maurice Bottiau, Franki Foundations - ABEF

IE-NET cursus

(2)

Deel 1. Inleiding – normatief kader

(N. Huybrechts)

Deel 2. Uitvoering Palen Categorie I, II en III

(M. Bottiau)

Deel 3. Uitvoering Palen Categorie IV

(N. Huybrechts)

Deel 4. Ervaringen bij de uitvoering van palen

(M. Bottiau)

(3)

Categorieën van palen

Pieux battus, vibrofoncés..

Heipalen, ingetrilde palen Pieux forés, puits,...

Boorpalen, putten

Pieux vissés Schroefpalen

Micropieux..

Micropalen

Verdringing Uithaling

(4)

VERSCHILLEND GEDRAG NAARGELANG TYPE PAAL

groep type

1 Verdringing

2 Beperkte

verdringing/ontspanning

3 Belangrijke ontspanning

4 micropalen

(5)

paalkopzakking

Belasting op paalkop

RU verdringing

verdringingspaal 10%

Grote drukken tegen paal verdichting

(6)

paalkopzakking

RU verdringing

verdringingspaal Paal met

grote grond- verwijdering 10%

Kleine drukken tegen paal, geen verdichting, risico aanzienlijke ontspanning

(7)

paalkopzakking

RU verdringing

verdringingsp aal

Paal met grote grond-

verwijdering 10%

- Bij zeer grote zakking: R_uverdr = R_uboor

- Bij conventionele bezwijkbelasting 10%.D : R_u,verdr > R_u,boor

- Bij dienstlast: R_s,verdr > R_s,boor

(8)

Paalclassificatie in België volgens de nieuwe richtlijnen

(9)

Several tools and equipment are used for the pile construction

driving screwing no

removal

soil removal impact driven vibratory static pushing partial full

GROUP I - driven xx x (x) - -

GROUP I - Screwed - - - xx - -

GROUP II driven x xx (x) - -

GROUP II screwed - - - x -

GROUP III - - - - (x) xx

impact driving diesel hammer hydraulic hammer internal falling hammer

(steam hammer) vibratory driving fixed moment

high frequency, variable moment static pushing several techniques

screwing (and pull down)

boring table on rig separate boring table

soil removal auger

excavation tools

EXECUTION METHODS

(10)

Categorie 1 PALEN MET GRONDVERDRINGING

(11)

(12)

driving screwing no removal

GROUP III - - - - (x) xx

screwing (and pull down)

excavation tools

Geheide palen

(13)

Pieux battus/Heipalen

▪ Pieux préfabriqués/Prefabpalen

▪ Béton/Beton

▪ Bois/Hout

▪ Acier (tubes, profilés,..)/Staal (buizen, profielen)

▪ Pieux battus moulés dans le sol/

In de grond gevormde palen

▪ Béton plastique/plastisch beton

▪ Béton sec/droog beton

(14)

• Nowadays usually prestressed high strength concrete , precast in factory and transported to site

• Full quality control

• Design prestress for handling and driving stresses

• Length is fixed and needs to be known beforehand

• No necking - bulging

Section D: 180, 220, 250, 290, 320, 350, 380, 400, 420, 450 and 500 mm

L: 50 to 80D

1 4

Geheide prefabbeton paal

(15)

(16)

1 6

Geheide prefabbeton paal

(17)

Less usefull when foundation level varies significantly over the site Tensile stress may lead to damage to pile (! From hard to soft ! )

1 7

Geheide prefabbeton paal

Driving can be done on water from barge Driving under water level is possible with hydraulic hammers

(18)

Difficulties when driving:

•Predrilling

•jetting !? Effect on ground ?

1 8

Geheide prefabbeton paal

(19)

Deepening of piles below ground level

Long steel anvil allows to reach depth of 4-5 m below GL

More difficult to guide

1 9

Geheide prefabbeton paal

(20)

Coupling of pile segments by special splicing device

Hercules koppeling

2

0

Geheide prefabbeton paal

Driving shoe for pinning precast pile in hard rock

(21)

In de grond gevormde heipalen

In de grond gevormde

heipalen d.m.v. een voorlopige voerbuis afgesloten aan de

basis met een verloren staalplaat

Diameters : 306 mm à 601 mm

Courante lengtes tot 32 m Plastisch beton

(22)

(23)

High bearing capacity

Through hard layer by heavy driving equipment

Length easy to adapt

Risk of necking / necking (very soft ground, waterflow, ..)

In de grond gevormde heipalen

(24)

Execution sequence

Typical diameter driving tube and bottom plate (mm)

273 (310, 330)

300 (330, 350, 365) 323 (365, 380, 400) 365 (400, 410, 435) 380 (435, 450, 465) 406 (465, 480, 500) 457 (520, 535, 560) 508 (560, 580, 615)

559 (615, 640, 660, 680) 610 (660, 680, 710, 740)

In de grond gevormde heipalen

(25)

Driving

Placing

Reinforcement

Concreting and extracting

In de grond gevormde heipalen

(26)

In de grond gevormde heipalen

Nominal diameter :

Db = diameter verloren staalplaat aan de punt (indien stijf genoeg) Ds = externe diameter heibuis

(27)

Static load tests: some results Mechelen (Bypass) – TUC RAIL

Conventional ultimate bearing capacity

ca. 90 à 98% of the calculated value according to the Belgian application of the NA-EC7

c.i.s.driven pile (vibro pile) temporary tube Ds = 508 mm, bottom plate Db = 550 mm

(28)

(29)

Conventional ultimate bearing capacity

ca. 72% of the calculated value according to the Belgian application of the NA-EC7

(30)

(31)

Heipalen met verbrede voet

De Franki paal

(32)

(33)

Execution sequence

De FRANKI paal

First Franki job Cockerill factory Ougrée

(34)

▪ Heipalen met verbrede voet/droog beton :

▪ S 0

▪ Consistentie beton : « Aardvochtig »

▪ Aangedamd

▪ Heipalen met verbrede voet/Plastisch beton

▪ Super Vibrex, Alpha, Kappa

▪ S3

▪ Basis gevormd d.m.v. herheien bovenaan de voorlopige voerbuis

Heipalen met verbrede voet

(35)

Socofonda – Vibro Alpha pile

Fundex – super-vibrex

Heipalen met verbrede voet alternatieven

(36)

Socofonda – Kappa pile

alternatieven

Heipalen met verbrede voet

(37)

Socofonda – Kappa pile

Paalbasisniveau : laagste niveau waarop de paalbasis zijn volledige sectie heeft

Nominale diameter :

Db = maximale diameter van de verbrede voet Ds = externe diameter heibuis

alternatieven

Heipalen met verbrede voet

(38)

So sure?

Long considered as the safest through measurement of the set.

However

◆Dynamic resistance should be preferred to set

◆Interpretation of dynamic resistance is still uneasy

◆Attention should be given to setup

In de grond gevormde heipalen

Comparison between measured and estimated bearing capacities using set-based dynamic formulae

(Billfinger, 2013)

(39)

Heien van palen

TOOLS

▪ Hydraulische hamers:

▪ Betere energy transfer

▪ Minder lawaai

▪ Hei-sequentie minder afhankelijk van de grond weerstand

▪ Diesel hamers:

▪ Robuust

▪ Geen externe power unit

▪ goedkoper Type of

hammer

Ram weight

Rated energy

Efficiency transfer Ratio (ETR)

KN KJ

Diesel <200 0.4- 600

31 %(steel) 25%(concrete) Hydraulic

drop hammers

<150 <200 55-85 %

Self-

monitored hydraulic

<1500 <200 55-85 %

After Rausche (2000)

(40)

Hydraulic hammer : Low noise impact Less vibration No exhaust gas

Adjustable energy and blow rate

Lower driving stresses Higher driving efficiency

Geheide palen

(41)

Alternatieven

voor inbrengen van prefabelementen

▪ Intrillen (Vibratory driving)

▪ Heibaarheid

▪ Draagvermogen ingetrilde elementen?

▪ Statisch indrukken (jacked piling)

▪ Reactie nodig

(42)

Geheide kokerpalen

(43)

Close ended : groupe I Open ended with soil plug : groupe I

Open ended without soil plug : groupe II

Geheide kokerpalen

(44)

Field of application

• aggressive soil conditions

• unstable soil, cavities …

• very soft soils (cu < 15 kPa)

• underground water current

• piles above ground or water level

• if high bending stiffness and shear resistance is required

• confined area’s : rehabilitation, renovation

Geheide kokerpalen

(45)

Geheide kokerpalen

(46)

Geheide kokerpalen

(47)

Geheide kokerpalen

(48)

JACKED PILES

Mega palen/pieu Mega

(49)

Jacked piles

Key issues

•Vibration-free installation

•Equipment capacity

•Relaxation

Lehane (2005): Relaxation Ru,static < Rinstallation

(50)

Grondverdringende Schroefpalen

(51)

GROUP III - - - - (x) xx

drilling table on rig separate drilling table

excavation tools

(52)

Historische perspectief

•Onstaan : einde van 19de eeuw

•Eerste generatie (jaren 1980) : vrij compacte verdringingsboren – specifieke installatieuitrusting (Fundex, Atlas) : Belgische oorsprong!

•Tweede generatie (jaren 1990):

•langere verdringingsboren die beperkt opwaarts grondtransport toelaten –De Waal, Omega

•Alternatieve systemen (eind jaren 1990 en later ): Olivier,…

Marktsituatie

•sinds de jaren 1980 enorme groei In België -Marktaandeel van 30 à 40 % (totale palenmarkt)

-Marktaandeel van 60 à 70 % (’gewone’

palenmarkt)

•Wereldwijd

-Marktaandeel wordt op 7% geschat -Groeiende belangstelling

Schroefpalen

(53)

▪ VOORDELEN

▪ Installatie zonder grondverwijdering

▪ Trillingsvrije en geluidsarme installatie (verstedelijkt gebied !)

▪ Hoog installatierendement, vooral 2e generatie systemen (150 à 300 m/dag tot zelfs 600 à 800 m/dag voor bep. firma’s in ideale

omstandigheden)

▪ Hoge draagvermogens vergelijkbaar met geheide systemen

▪ NADELEN

▪ Relatief hoge machinevermogens benodigd

▪ Penetratie van harde/dichtgepakte (tussen)lagen soms probleem

Grondverdringende Schroefpalen

(54)

▪ Emergence of a range of systems, types and labels

▪ Application of Displacement Auger Piles in more soil conditions

▪ Shape of the displacement auger and Execution process of the different systems existing on the market can present large differences in the

actual ratio of displacement as well as in the final result

Grondverdringende Schroefpalen

(55)

Grondverdringende Schroefpalen

(56)

Vergelijkende proefcampagnes te Sint-Katelijne- Waver & Limelette (in kader van EC7

toepassingsdocument)

▪ Coördinatie en proefgedeelte WTCB

▪ Partners : KUL (Prof. J. Maertens) & UCL (Prof. A.

Holeyman)

▪ Financiële steun : FOD Economie

▪ In samenwerking met 5 paalbedrijven:

- Fundex

- Franki Geotechnics B - Olivier

- De Waal - Socofonda

▪ Uitgebreid proefprogramma op gvs schroefpalen en geheide prefabpalen (als referentie)

→ Basis voor opstellen van toepassingsdocument EC 7

Grondverdringende Schroefpalen

(57)

Screw piles : Systems

• Shape of the auger – movement of the soil

• Shape of the auger – effect on end bearing

• Shape of the auger – shape of the final pile

• Power of the piling rig to Rotate

• Power of the piling rig to Push – force auger penetration

• Casting method (pressure) of the concrete placement

• Control of auger extraction – effect on the shape of the final pile

(58)

Grondverdringende Schroefpalen

Infofiche WTCB

(59)

Atlas schroefpaal

WTCB infofiche 67.5.1.2.1.2

(60)

D_b= max. diam screw D_s= max. diam. tube

Base level = level max. diam lost screw

Fundex schroefpaal

(61)

Omega pile De Waal pile

Reverse flighting

Soil

transport

Displacement screw piling second generation

(62)

De Waal schroefpaal

Base

D_s=D_b= max. diam. screw auger Base level = top lost bottom plate

(63)

Omega schroefpaal

D_s=D_b= max. diam. screw auger Base level = top lost bottom plate

(64)

Olivier screw pile

D_s=D_b= max. diam screw auger

Base level = level 1 rotation above lost bottom plate

(65)

En een aantal andere systemen…

(66)

Small details can make…

A big difference

(67)

Systems details

(68)

(69)

Static load tests: results SKW (o.c. Clay site)

0

5

10

15

20

25

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80

Q_meas/R_cu,calc ( Average CPT- NA-EC7 method)

S0/Db (%)

A1-prefab A4-prefab A2-Fundex A3-Fundex B1-De Waal B2-De Waal C1-Omega C2-Omega B4-Olivier B3-Olivier C4-Atlas (C3-Atlas)

s0 = 10%Db

- Global coeff. Screw piles :0.78 – 0.90 (0.98) - Global coeff. Prefab : 0.86 – 0.91

Normalised load-settlement curves

(70)

Static load tests: results LIM (Sand site)

Site Limelette I & II

0

5

10

15

20

25

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80

Q_meas/R_cu,calc (NA-EC7 method, ab = as = 1, Dnom)

Sb/Db (%)

B1-Prefab

B2-Prefab

A1bis-Fundex

A4-De Waal

C4-De Waal

A3-Omega

C3-Omega

A2-Olivier

C2-Olivier (no sb-meas.)

B3-Atlas

B4-Atlas

s0 = 10%Db

- Global coeff. Screw piles :0.8 – 1.0 - Global coeff. Prefab : 1 & 1.12

(71)

Static load tests: some results LIM (Sand site)

Site Limelette I & II

0

5

10

15

20

25

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80

Q_meas/R_cu,calc (NA-EC7 method, ab = as = 1, Dnom)

Sb/Db (%)

B1-Prefab B2-Prefab A1bis-Fundex A4-De Waal C4-De Waal A3-Omega C3-Omega A2-Olivier

C2-Olivier (no sb-meas.) B3-Atlas

B4-Atlas

P4-tubular (LIM I) P8 - Prefab (LIM I) P12 - Driven c-i-s (LIM I)

Prefab 29x29 (1995/96) Tubular pile 0.272m (1995/96)

Franki 0.42/047 (1995/96)

(72)

Site Limelette WTCB

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

0 2 4 6 8 10 12 14 16

Schroefpaalproject Limelette II Horizontale Grondrukcoëfficient KD (-)

Diepte (m)

Gemidd. KD maagdelijke terrein KD langs prefab

Gemidd. KD langs schroefpalen

(73)

Grondverdringende Schroefpalen

Infofiche WTCB

(74)

Geschroefde KOKERPALEN

(75)

Geschroefde kokerpalen

Ds : 219mm, 273 mm, 324 mm Db : 350 …650 mm

(76)

Voordeel

Penetratie van harde/dichtgepakte (tussen)lagen mogelijk

D

_s

?

Geschroefde kokerpalen met groutinjectie

(77)

Categorie 3 PALEN MET GRONDVERWIJDERING

(78)

BOORPALEN

(79)

soil removal impact driven vibratory static pushing partial full

GROUP III - - - - (x) xx

impact driving diesel hammer

hydraulic hammer internal falling hammer

excavation tools

BOORPALEN

(80)

BOORPALEN

(81)

Bor ed Piles

carry very high vertical and horizontal loads deal with most ground conditions

But:

◆Reliability of each pile is essential

◆The different methods used to drill the hole will play an important role on the contact between the pile and the surrounding soil

◆Cleaning of the pile basis is of outmost importance on the base resistance

◆Concreting phase

◆Influence of the drilling fluid both on execution reliability and on bearing capacity

◆Structural integrity is a critical point Able to

(82)

Bored piles

One name=different systems

82

(83)

Principle of execution

Bruface, Geotechnical Eng., C. Bauduin

België: meestal onder voerbuis

Diamètres/diameters:

0,62 m, 0.75m, 0.9m, 1.07m, 1.28m, 1.5m, 2.00 m

Bétonnage au tube

plongeur/betonneren met een plunjerbuis:

C25/30 ou C30/37 S4

Verwerkbaarheid – tijdsduur van het betonneren!

BOORPALEN

(84)

BOORPALEN

Voorafgaandelijk ingeboorde of ingetrilde stalen casing

Droge boring (zonder casing) Steunvloeistof (bentoniet, polymeren)

Tijdelijke stalen verbuizing/ casing

(85)

Support of borehole with drilling fluid Bentonite slurry

BOORPALEN

• to prevent water inflow (cake)

• to support ground pressure

Bentonite level min 1,5 to 2 m above ground water level

Casing tube on top few m to avoid local instability Requirements on properties of bentonite slurry

(viscosity, unit weight, sand content...: see EN 1536 );

check properties during pile execution

(86)

Bored piles: support steel casing –thickwalled steel ring casing elements

• Thick walled steel tubes connected with special dowels, placed during excavation and retrieved during pouring of concrete

• Casing over full or part of pile length

• Water of bentonite to equilibrate the ground water pressure

BOORPALEN

(87)

Bored piles: support steel casing –thickwalled steel ring casing elements

87

Placed by vibrator before start of excavation Bored piles: vibratory driven steel casing tube

BOORPALEN

(88)

Excavation

spiraalboor

grijper

bucket

spiraalboor

grijper

bucket

Auger at end of kelly bar for “soft” ground

BOORPALEN

(89)

spiraalboor

grijper

bucket

Bucket: turning Excavation

BOORPALEN

(90)

BOORPALEN

Soft Soils

(91)

Rock: bucket with rock teeth and chisel

BOORPALEN

Bucket met bijtelsvoor harde rots chisel om rots te breken

(92)

Reinforcement

Prefabricated (welded) cages, transported to site Equiped with tubes for sonic testing

BOORPALEN

(93)

Placement of cage in borehole Coupling of two cages Wapeningen

BOORPALEN

(94)

Concrete pouring

Pour through tremie pipe to avoid segregation

Pipe at pile bottom, concrete pushes aside residues and not cleaned deposits on bottom Continuous concrete pouring operation while tremie pipe remains 1,5 to 2 m in fresh

concrete; pipe is retracted during pouring

94

BOORPALEN

(95)

Concreting: mix and properties

Mix proportions (acc EN 1536)

Cement content

− Placement in dry conditions

− Placement in submerged conditions

≥ 325 kg/m³

≥ 375 kg/m³

Water – cement ratio (W/C) < 0,6

Fines content, d< 0,125( mm (inclusive cement)

− Coarse aggregate d > 8mm

− Coarse aggregate d≤ 8 mm

≥ 400 kg/m³

≥ 450 kg/m³

Consistency rate for fresh concrete in different conditions (acc EN 1536)

Flow diameter range mm

Slump range mm

Typical conditions (examples) 460 ≤ f ≤ 530 130≤ H ≤ 180 Concrete placed in dry conditions 530 ≤ f ≤ 600 H ≥ 160 Placed by pumping or

Concrete placed in submerged conditions under water by tremie

570 ≤ f ≤ 630 H ≥ 180 Concrete placed by tremie in submerged conditions under a stabilising fluid

Note: the measured slump (H) or flow diameter F is to be rounded up to the nearest 10 mm

BORED PILES

(96)

Na injectie

Om de stijfheid en het draagvermogen te verbeteren

Base grouting

96

BOORPALEN : Bijzondere uitvoeringstechnieken

Shaft grouting

(97)

In overgeconsolideerde klei om het basisdraagvermogen te verbeteren Underreaming

97

BOORPALEN : Bijzondere uitvoeringstechnieken

(98)

Bored piles : Drilling

– Full casing drilling:

• sufficient soil plug in order to limit the potential decompression of the surrounding soil

• smoother shaft will be realized.

– Drilling fluid :

• temporary under-pressures will develop above the drilling tool

during excavation or under the grab during lifting (Van Weele ,1988).

• Attention to lifting speed.

• Polymer vs bentonite

– Borehole roughness in soft rocks and cohesive soils.

(99)

Bored piles execution

• Cleaning of the pile basis:

– Effect on base resistance

– Time-effects of the bored pile construction (Poulos (2003))

• Concreting phase.

– Rate of casting, fluidity, permeability of both concrete and soil.

– Excess porewater pressures can drain off along the shortest draining path through the bentonite cake into the soil.

– Potential interaction between drilling fluid and concrete. (Ata and

O’Neill (2000))

(100)

Bored piles testing

• NDT : Non-Destructive Test methods to evaluate

structural integrity is pulse echo or low strain testing

• CSL : Crosshole Sonic Logging uses the propagation time

and relative energy of an ultrasonic pulse

• Core drilling of the base of

the pile (or the defect zone

identified by CSL)

(101)

TIP: Thermal Integrity Profiling (TIP)

(102)

CFA palen

(103)

Standard :

diameter 350 à 600 mm

Lengtes tot 22.00 m Risico van

ontspanning

Tweede generatie Diameters tot 1.2 m Lengtes tot 40.00 m Beperking van de ontspanning

CFA (Avegaar) palen

(104)

Heel gevoelig voor grondontspanning

▪ Over-augering: te grote grondverwijdering

▪ In onsamenhagende gronden

▪ Gelinkd aan het vermogen van de machine

▪ Equipment capacity

▪ Concreting phase :

▪ Probleem van het gecontroleerd terugtrekken

▪ Te snelle optrekken -> onderdrukken en ontspanning

▪ Systeem is zeer uitvoerings- en operatorgevoelig

▪ Plaatsing van de wapening na betonneren

CFA palen

(105)

Augercast : Over-augering

Screwing ratio SR= n.p/V

with

• n is the revolution rate of the auger (rpm)

• p is the pitch of the auger (meter p round)

• V is the rate of penetration of the auger (m/min)

Mechanism of over-augering (Viggiani, 1993)

(106)

• Consider the possibility of upward soil movement, after excavation, along the auger flanges ;

• The occurrence of excessive flighting is more likely to occur with large diameter augers

• Steepening of the flight angle may help reducing soil loosening

• Excessive flighting reduces as the shear angle of the undisturbed soil increases.

Flemming (1994)

CFA palen

(107)

CFA : Monitoring tijdens uitvoering

CFA palen (schroefpalen in het algemeen!)

– Inclinatie – Koppel

– Pull down kracht – Penetratiesnelheid – Rotatiesnelheid

– Betonneer druk

– Betonneervolume

– Terugtreksnelheid

(108)

« Verbeterde »

CFA palen: beperking van de grondonstpanning

▪ CFA palen van de 2e generatie (PCS/Starsol…)

▪ Monitoring v.d. uitvoeringsparameters

▪ Screwing ratio:

▪ Grotere koppels (>20 Tm) en rotatiesnelheden (>8 to 10 rpm)

▪ pull down (> 10 T)

▪ Betonneerfase:

▪ Betonneren onder gecontroleerd druk

▪ Betonpompen van hoge capaciteiten (50 tot 70 m3/h)

▪ Telescopische betonneerbuis

▪ CFA palen met grote centrale kern (PCS-l)

▪ CFA palen met tijdelijke verbuizing

(109)

allows larger diameter and length of reinforcement cage

CFA palen met grote centrale kern (PCS-l)

(110)

Cased auger pile, reverse rotation

CFA palen met tijdelijke verbuizing

•Twee boortafels: casing en avegaar

• Opgelet : uitgeboorde grond valt van grote hoogte

• Kan doorheen

metselwerk geboord worden

• Wordt veel toegpast voor de realisatie van secanspalenwanden

(111)

CFA palen

(112)

Case study : Tessenderlo

• Augercast with large stem – partial displacement

• Diam. 600/324 mm – 17,50 m deep

• Bearing capacity 2500 kN

• Compact glauconitic sands

(113)

(114)

Tessenderlo : preliminary test program

• 5 test piles

• Static and dynamic load tests

• Test load = 6000 kN

• Heavy duty equipment (Torque 220 kNm-

pulldown 200 kN)

• Execution quite

unsuccessful > 1,5 hours

drilling

(115)

-30 -25 -20 -15 -10 -5 0

0 500 1000 1500 2000 2500 3000 3500 4000 4500

s (mm)

Q (kN)

T1

Vertical static load test & Capwap Analysis Dynamic Load test

Cycle 1 Cycle 2 Capwap Analysis

(116)

0 2 4 6 8 10 12 14 16 18 20

0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1

an = max (S30'/log(2))

Q/Qmax

T1 Creep Analysis

Qc/Qmax = +-0.85 Qc= 0.85 x 2250 kN Qserv = Qc /1.4 = 1366 kN

(117)

Case study : Mechelen RER site

• Augercast piles with large stem

• Diam. 600/324 mm

• CPT before and after installation

• Full instrumented load tests

(118)

Case study : Mechelen RER site

(119)

Case study : Mechelen RER site

(120)

-120 -110 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0

0 500 1000 1500 2000 2500 3000 3500 4000 4500

Pile base displacement sb -end of loading step (mm)

Average load per loading step Q (kN)

Q KW04 Qb KW04 Qs KW04 Q KW15 Qb KW15 Qs KW15

10 % Db

mogelijks beïnvloed door ontlasten en herbelasten

Case study : Mechelen RER site

(121)

(122)

After Theys (2002)

CPT - CFA with casing

-5.00 0.00 5.00 10.00 15.00 20.00

0.00 10.00 20.00 30.00 40.00

qc (MPa)

Depth (mTAW)

Electrical CPT's before Mechanical CPT's before Mechanical CPT's afterwards

Soil loosening at the pile tip

CFA palen met tijdelijke verbuizing

(123)

Categorie 2 PALEN MET WEINIG

GRONDVERDRINGING OF ONTSPANNING

(124)

Piles with

Limited

soil relaxation

Intermediate systems Difficult to categorize

PALEN met weinig grondverdringing of ontspanning

(125)

soil removal impact driven vibratory static pushing partial full

GROUP III - - - - (x) xx

impact driving diesel hammer

hydraulic hammer internal falling hammer

excavation tools

(126)

PILES WITH LOW DISPLACEMENT AND LIMITED RELAXATION

▪ Thin steel elements

▪ non plugging open ended steel tubes

▪ sheetpiles

▪ H profiles

▪ Piles that involve large extraction (decompression) but foreseen of measures to mitigate decompression

▪ auger piles with overpressure

▪ tubular cased auger piles

▪ large diameter stem auger piles

▪ Screw piles which have not been validated through the normalisation commission

Driven or vibrated

Auger screwed

(127)

Open ended steel tube

Bearing capacity by inner and outer friction

Large diameter, great depth;

great bending capacity In parts that are welded together

Durability (by sacrificial corrosion allowance; by cathodic protection)

Thin steel elements

(128)

Pile driving from SEP using hydrohammer and guide frame

Jetty on open ended steel rock socketed piles

1 2 8

Open buizen

(129)

H profile: for specific applications “wide flange bearing piles”

• Difficult access (water...)

• High bending moments due to imposed ground displacement

Thin steel elements

(130)

Systems to increase bearing capacity: provide some surface for “end resistance” by plugging

(131)

A trekkop

B elastomeren C excenters

D verstelmotor (niet

zichtbaar) met tandwielen E tandwielkast

F klem

G klembekken

Vibrator brings vertical vibrations into pile that “loosens” the ground

1 3

1

Vibratory driving

(132)

Vibratory driving

▪ Advantages:

▪ Which vibro-hammer could drive the pile to the required depth?

▪ Premature refusal can often be encountered.

▪ Fast and cheap

▪ Allows to retract piles and sheetpiles

▪ Penetration prediction quite difficult, based on:

▪ experience

▪ models

▪ Disadvantages:

▪ Produces important Noise and Vibrations

▪ Debate concerning effect of vibratory penetration on static pile bearing capacity;

▪ Comparative tests are not clear to define “one final rule”

▪ Plugging of open tubes ?

▪ Sometimes: redrive by impact hammer

(133)

After Borel et al (2002)

Vibratory driving

(134)

Schroefpalen

▪ Schroefpalen met verdringing zonder infofiche = categorie 2.

▪ CFA palen met voorzieningen om de ontspanning te beperken

(135)

LOOKOUT

Many systems

▪ All installation methods may prove to be inadequate in function of the soil conditions.

▪ Aspects governing the pile installation should all be considered.

▪ The response of some types of soils to the solicitation of pile installation procedure, can be dramatically different than expected.

▪ Execution systems are classified into generic groups but they are in constant evolution, and small details are sometimes changed resulting in major differences.

(136)

It’s all about

Reliability

(137)

MATERIALEN

Algemene

beschouwingen

(138)

MATERIALS and Structural considerations

▪ Concrete

▪ Composition

▪ Rheology

▪ Workability

▪ Stability

▪ Steel

▪ Reinforcement cages stifness

▪ Tubes, welding…

▪ Position, cover,…

(139)

Concrete for deep foundations

(140)

▪ Placement mostly in immersed conditions

▪ Tremie pipe or hollow stem of auger –Importance of workability/fluidity

–Stability of the mix against segregation or bleeding –Technological aspects linked with

reinforcement/cover/tolerances…

Self-placing/self-compacting concrete

▪ Other aspects:

▪ Quantity/continuity

▪ Supply cadence

Specific aspects

(141)

(142)

▪ Revised version of NBN EN 206-1:2013 : specification, performances, production and conformity of concrete

▪ Annex D : additionnal requirements for concrete for special geotechnical works (formerly in EN 1536:2010 and EN

1538:2010)

Revision of EN 206-1

(143)

Example bored piles

Placement condition

Cement content [kg/m³]

Water-cement ratio

[-]

Slump [mm]

Flow diameter [mm]

Dry ≥ 325 ≤ 0.60

and in compliance with provisions valid for specified

exposure classes

150 ± 30 500 ± 30 submerged under

water,

≥ 375

180 ± 30 560 ± 30 under a stabilizing

fluid 200 ± 30 600 ± 30

(144)

Recent evolution of concrete production

(145)

Monitori ng of pile exec ution

• Know what happens

• Prove reproducibility

• Track anomalies

Testing and monitoring

(146)

Testing and monitoring

It is essential to document

and verify proper pile

execution Pile performance depends on

❖local conditions

❖equipment & system details

❖crew

Increase of reliability

(147)

Monitoring of pile execution

▪ Automated recording of driven pile installation parameters

▪ Dynamic monitoring of driven piles

▪ Automated monitoring of augercast and screwed pile installation

▪ Detailed annotation of any abnormality during execution, unexpected phenomenon, response of soil during

installation (subsidence, uplift, lateral movement, …) or concreting (sudden loss of concrete, abnormal over-

break,..) during the execution of bored piles.

(148)

Monitoring also includes

▪ Execution of soil tests such as CPT after pile installation (Van Tol, 2009):

▪ Redesign of piles based on CPT’s performed after pile installation can be beneficial

▪ For bored and auger piles, CPT’s should be executed at different distances and around the tested piles.

▪ Integrity testing

▪ Sonic logging

▪ Impedance testing

▪ Thermal profiling

(149)

▪ Design Pile Load tests:

▪ Instrumented

▪ Define installation parameters aligned with detailed installation method

▪ Control load testing

▪ Static

▪ Dynamic or statnamic

▪ Execution control

Testing and monitoring

(150)

Reliability?

❖adequate understanding and documentation of the local soil conditions

❖correct specifications of expected performance (capacity, deformations, …)

❖ability of the contractor to demonstrate prior experience in similar ground conditions

❖verified system performance

❖in-situ documentation and monitoring of pile execution in order to ensure reproducibility

❖pile performance testing

(151)

ENGINEERING JUDGMENT

And don’t forget