Bolivia driven vibrated piles k. rainer masssarsch

Vibrated and Driven Piles

K. R. Massarsch Geo Risk & Vibration AB, Stockholm, Sweden

Overview

•  Pile classification systems •  Driven pre-‐‑formed piles •  Advantages and disadvantages •  Aspects of pile installation •  Aspects of driven pile installation •  Vibratory driving

Pile Classification System 1.  Method of installation: bored/augered,

continuous augered, driven, screw-‐‑in 2.  Degree of displacement: large, small, non 3.  Pile material: concrete, steel, timber,

composite 4.  Manufacture: in-‐‑situ, preformed, combined 5.  Support during pile installation: no

support, temporary casing, permanent casing, drilling mud, soil concrete/grout

6. Enlarged base

Driven Pre-‐‑formed Piles Probably the oldes pile installation method

Driving of Concrete Piles

Advantages of Driven Pile Installation

•  Material of pile can be inspected before it goes into the ground

•  Stable in "ʺsqueezing"ʺ ground •  Low risk of damage by ground heave

when driving adjacent piles •  Construction procedure unaffected by

ground water •  Can be readily carried above ground level,

especially in marine structures •  Can be driven in very long lengths

•  Hard driving may damage or break pile •  Uneconomical if pile design governed by

handling/driving stresses rather than permanent loading

•  Noise and vibration during driving •  Displacement of soil during pile driving

Cannot be driven in very large diameters •  End enlargements not always advantages •  Cannot be driven in low headroom

conditions

Disadvantages of Driven Piles

Aspects of Pile Installation

Driving methods: impact methods or vibratory driving

Driving components: pile shoes, jointing, splicing, pile helmets & packing

Driving aids: pre-‐‑blasting, pre-‐‑drilling, pre-‐‑driving, jeQing

Post treatment: re-‐‑driving, grouting

Pile Driving Hammers

Vibratory hammers Electric vibrators Hydraulic vibrators

Impact hammers Air and steam hammers: single-‐‑acting hammers, double-‐‑acting hammers Diesel hammer Drop hammer Hydraulic hammer

Diesel Hammer Hydraulic Hammer

Pile Materials

Timber Concrete: reinforced and prestressed Steel: tubular, steel profiles, sheet piles Composite: steel – concrete -‐‑ timber

Timber Concrete

Steel Piles

Manufacture of Pile

Cast in-‐‑situ: concrete Preformed: timber, steel, concrete Combined: concrete, steel etc. Jointed piles

Cast in-‐‑situ Driven Pile

Pre-‐‑formed Spun Piles

Swedish Concrete Pile Joint

Driving Aids

Pre-‐‑drilling: auger Pre-‐‑driving: vibrator or hammer JeTing: water and/or air Grouting: cement and/or bentonite Pre-‐‑blasting

Pre-‐‑boring with Auger

Grouted Driven Pile

JeQing of Driven Piles

Vibratory Driving Systems

Significance of Vibration Frequency for Driving of Piles and Sheet Piles

Why is Vibration Frequency of Importance

for Pile Driving?

•  Driving efficiency: pile penetration is affected.

•  Intensity of ground vibrations: emitted to surroundings.

•  Pile capacity: change of stress conditions in soil.

FV = Me ω2

Centrifugal Force, Fv

s =Me

mt

Displacement Amplitude, s

Me =ms eEccentric Moment, Me

ω = 2π f

Circular frequency, ω

Important Vibrator Parameters

Electronic Monitoring and Control

Geophone

0

10

20

30

40

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

DEPTH, m

TIME, h:min:s

Depth m Depth m

Pile Penetration Depth

0

10

20

30

40

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

PRESSURE, MPa

TIME, h:min:s

Frequency Hz Depth m

DEPTH, m

Variation of Frequency

0

10

20

30

40

0

10

20

30

40

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

FREQUENCY, Hz PRESSURE, MPa

TIME, h:min:s

Pressure MPa Frequency Hz

Depth m

DEPTH, m

Variation of Hydraulic Pressure

0

10

20

30

40

0

10

20

30

40

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

FREQUENCY, Hz VELOCITY, mm/s PRESSURE, MPa

TIME, h:min:s

Pressure MPa Frequency Hz

Depth m Geo z mm/s

DEPTH, m

Ground Response due to Frequency Variation

0

5

10

15

20

25

0 5 10 15 20 25 30 35 40 VER

TICAL VIBRA

TION VEL

OCITY , m

m/s

VIBRATION FREQUENCY, Hz

Vertical

Penetration

Ground Vibrations during Vibratory Driving

0

5

10

15

20

25

0 5 10 15 20 25 30 35 40 VER

TICAL VIBRA

TION VEL

OCITY , m

m/s


Vertical

RESO

NANCE


0

5

10

15

20

25

0 5 10 15 20 25 30 35 40 HORIZO

NTA

L VIBRA

TION VEL

OCITY, m

m/s


Radial


0

5

10

15

20

25

0 5 10 15 20 25 30 35 40 HORIZO

NTA

L VIBRA

TION VEL

OCITY, m

m/s


Tangential


F GEOPHONE

Toe resistance

Shaft resistance

mS

kS dS

Calculation of Resonance Frequency of Pile Vibrated into a Soil Deposit


mP

mS

kS

kT dT

dS

dM

kM

mS

kS

kT dT

dS

dM

kM


mP

F(t)

uP (t)

F(t)

uP (t)


mP

mS

kS

kT dT

dS

dM

kM

uS (t)

FREQUENCY, Hz

DISPL

ACEM

ENT,

mm

Eccentric moment: me=10 kgm -‐‑ Shear wave speed: cS=225 m/s:

Resonance frequency

Absolute

Imaginary

Real

Resonance Frequency of Vibrating Pile

Start-‐‑up of vibrator without vibrations to required speed

without vibrations

Resonance-‐‑free Vibratory Driving

Gradual increase of vibration amplitude rotating lower row of

masses against upper row.


Maximum vibration amplitude of vibrator at largest eccentricity


Vibration-‐‑free Start-‐‑up of Vibrator

Sheet Pile Driving in Vibration-‐‑sensitive Area


Monitoring of ground vibrations by geophone Sheet pile driving with resonance-‐‑free, high frequency vibrator

Vibration-‐‑sensitive

embankment


Monitoring of ground vibrations by geophone Sheet pile driving with resonance-‐‑free, high frequency vibrator

Summary and Conclusions

•  Driven piles are in many cases a cost-effective foundation solution.

•  Driving piles requires competent personnel and suitable equipment.

•  Vibratory driving can be efficient in suitable ground conditions.

•  By adjusting the operating parameters of modern vibrators, pile driving and ground compaction can be optimized.

•  The performance of vibrators can be monitored and opitmized using different types of sensors.

Thank You!

SWEDISH PILE DRIVING TECHNOLOGY

Engineering

Bolivia driven vibrated piles k. rainer masssarsch