massarsch uevos desarrollos en pilotes de fundación

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New Developments in Pile Foundations

K. Rainer Massarsch

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Overview of Presentation

Auger Cast Piling (CFA) MethodRisk of Soil De-compressionMonitoring of Auger Cast Pile InstallationAuger Cast Pile with Expander Body Displacement Auger PilesVibrated Steel Piles with Expander BodySettlement-reducing Conical Concrete Nails

International DFI Conference – Stockholm 2014

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Auger Cast Pile (CFA-pile)

Start of auger penetration

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Auger Cast Pile (CFA-pile)

Auger penetrationSoil heave on ground surface

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Auger Cast Pile (CFA-pile)

End of auger penetrationCompetent layer has been reached

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Auger Cast Pile (CFA-pile)

Start of grouting processduring auger extraction

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Conventional Auger Cast Pile (CFA-pile)

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Auger Cast Pile (CFA-pile)

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Small and Large Stem Auger

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Decompression due to low penetration speed

Stiff layer

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Decompression due to high extraction speed

Risk of necking

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Risk of Soil Decompression during Penetration

d l

D

vcrit

Volume of stem

Volume of stem and flight

Volume of pumped soil

Critical penetration rate

n

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Critical Penetration Speed – Soil De-compression

No de-compression

De-compression

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Monitoring of Pile Installation

PENETATION

• Pushing force• Penetration speed• Torque• Hydraulic

pressure

EXTRACTION

• Concrete pressure

• Concrete volume• Extraction speed

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Illistration of Installation Record

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Determination of Pile Penetration Resistance

From drilling parameters the actual soil resistance is determined.

This information is used to establish required depth of penetration

Required pile length

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Installation of Reinforcement

Placement of reinforcement can be critical for auger pile quality!

Single bar – cage – fibre concrete?

• Insertion procedure can damage borehole wall

• Full pile reinforcement may not be necessary

• Use straight reinforcement cage• For long piles: use guiding tube• Use vibrator if necessary• Large-stem piles facilitate

installation• Fibre concrete avoids problems

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Applications of Expander Body

Expander Body can be combined with

conventional piling methods:

• Vibrated steel tube pile

• Continuous flight auger pile (CFA)

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Pressuremeter Test

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Inflation of Expander Body

Expander Body similar to

Pressure Meter Test

Grout volume and inflation pressure are

measured

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After Expansion

TYPE LENTH DIAMETER TOE BEARING

AREA

SKIN AREA

VOLUME

m m mm2 mm2 m3

EB 610 1.0 0.6 0.28 1.43 0.21

EB 612 1.2 0.6 0.28 1.83 0.27

EB 615 1.5 0.6 0.28 2.38 0.36

EB 815 1.5 0.6 0.50 3.17 0.63

EB 820 2.0 0.8 0.50 4.42 0.88

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EB Grouting Recording

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Grouting Pressure and Grouting Volume, EB 600

Filling of EB

Expansion of EB

Soil displacement

Expansion pressure

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Post-grouting of Expander Body

Post-grouted Zone

Expander Body shortens during

inflation

Inflation of Expander

Body

Full expansion

of Expander Body

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Auger Cast Pile with Expander Body

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Advantages of CFE + EB

Reduced pile lengthKnown shape of pile baseRecompression of soil at and below pile basePost-grouting of pile base avoids soil de-

compression Reduce pile shaft diameterQuality monitoring and control

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Vibration Pile Test with Expander Body

Allermöhe, GermanyExpander

BodySteel tube piles12 and 16 m long

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Comparison Steel Tube Pile and Expander Body Pile

ExpanderBody

Steel tubepile

Medium dense sand

Loose sandOrganic layers

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Comparison Steel Tube Pile and Expander Body Pile

ExpanderBody

Steel tubepile

Medium dense sand

Loose sandOrganic layers

Steel tube pile

ExpanderBody

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Design of Bearing Capacity based on CPT

Swedish Design Recommendations

EB toe resistance: Sand: sBase = 0.5 qc < 5MPaSilt and clay: s Base = 1.0 qc

EB shaft resistance: sShaft = 0.005 qc<50 kPa

D

qc

D

3D

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Bearing Capacity from CPT Test

SHAFT RESISTANCE

TOE RESISTANCE

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Installation of Vibrated EB Pile

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Pile Test Loading

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Steel Tube Pile vs. Expander Body

Pile length: 12 m

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Advantages of Vibrated Steel pile with EB in Friction Soils

Quick and environmentally-friendly installation

End-driving to “set” not required as EB compresses soil

Known shape of pile basePost-grouting of pile base avoids soil de-

compression Quality monitoring and control

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Gewerbehof Halle, Germany

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Vibrated Conical Nails – Halle Business Center, Germany

Difficult ground conditions with variable fill material

Installation close to existing buildingConical concrete nails vibrated to 9 m depthHigh driving frequency (38 Hz)Vibro-compaction at end of nail installationLoad testing of concrete nail capacity

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Settlement Reduction by vibrated Concrete Nails

Alternative foundation

solution to stone columns or piles

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Cone Penetration Test, CPT

Cone Resistance, MPa

Friction Ratio, %

De

pth

, m

Mixed fill

Dense sand

Stiff clay and

lignite

Medium dense sand

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Design Concept of Conical Nail Foundation

Determine settlement of unimproved ground using tangent modulus method

Are the calculate settlements acceptable? Calculate load which corresponds to acceptable

settlement Calculate the excess load to be supported by conical

nails Determine the number and distribution of conical nails

This design approach achieves load-sharing with nail safety factor FS =1.0!

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Load from Surface Foundation

Increasedconfiningstress aroundnails

Q

Load fromnails

Load fromfooting

2

1

Load from Footing

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Load-sharing between Surface Foundation and

Concrete Nails

Increasedconfiningstress aroundnails

Q

Load fromnails

Load fromfooting

Load from Concrete

Nails

Load from Footing

Factor of Safety of Concrete Nails

Fs = 1.0

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Ground Vibrations During Vibratory Pile Driving

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Variable Frequency Vibrator

NO ECCENTRIC MOMENT DURING START-UP AND

SHUT-DOWN OF VIBRATOR

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Variable Frequency Vibrator

STRONG VIBRATIONS DURING DRIVING PHASE

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Avoids resonance peaks of ground vibrations!

Resonance-free driving

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Conical Concrete Nails

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VIBRATION-MONITORING

INSIDE BUILDING

ELECTRONIC PROCESS CONTROL

VIBRATOR MS100

VIBRATION MONITORING

UNIT

CONCRETENAIL

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Monitoring Resonance Compaction

Geophone

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Installation of Concrete Nail

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Frequency vs. Ground Response

0

2

4

6

8

10

12

14

16

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5 10 15 20 25 30 35

FREEQUENCY, Hz

VE

RT

ICA

L P

AR

TIC

LE

VE

LO

CIT

Y, m

m/s

ResonanceFrequency

Penetration Frequency

Extraction

Frequency

Penetration

Frequency

Compaction

Frequency

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0

100

200

300

400

14:22:26 14:23:18 14:24:10 14:25:02

Time, hrs:min:sec

Pressure, bar

0

10

20

30

40

Frequency, HzDepth, m

Velocity mm/s

Pressure bar Frequency Hz

Depth m Geo z mm/s

Example of Compaction Monitoring

Pressure MPa

Pressure MPa

40

30

20

10

Time h:m:s

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Concrete Nails after Installation

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Load Test of Concrete Nail and Steel Tube Pile

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0

0,5

1

1,5

2

2,5

0 50 100 150 250 300 350

LOAD, kN

DE

FO

RM

AT

ION

, mm

Steel tube

Concrete Nail

Results of Loading Test

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Advantages of Vibrated Concrete Nails

Can be installed efficiently in most soils by vibrator

Conical shape and small toe reduces driving resistance

Conical shape increases soil compactionConical shape provides high lateral

resistance near ground surfaceKnown shape and material properties

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Thank you!