Post on 15-Aug-2015
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
VIBRATION FREQUENCY, Hz
Vertical
RESO
NANCE
Ground Vibrations during Vibratory Driving
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
VIBRATION FREQUENCY, Hz
Radial
Ground Vibrations during Vibratory Driving
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
VIBRATION FREQUENCY, Hz
Tangential
Ground Vibrations during Vibratory Driving
F GEOPHONE
Toe resistance
Shaft resistance
mS
kS dS
Calculation of Resonance Frequency of Pile Vibrated into a Soil Deposit
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
Calculation of Resonance Frequency of Pile Vibrated into a Soil Deposit
mP
F(t)
uP (t)
F(t)
uP (t)
Calculation of Resonance Frequency of Pile Vibrated into a Soil Deposit
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.
Resonance-‐‑free Vibratory Driving
Maximum vibration amplitude of vibrator at largest eccentricity
Resonance-‐‑free Vibratory Driving
Vibration-‐‑free Start-‐‑up of Vibrator
Sheet Pile Driving in Vibration-‐‑sensitive Area
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
Sheet Pile Driving in Vibration-‐‑sensitive Area
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