1er Congreso - Seminario Internacional de Fundaciones Profundas - Santa Cruz, Bolivia - 2013

1. New Developments in Pile
Foundations
K. Rainer Massarsch
1

2. Overview of Presentation
 Auger Cast Piling (CFA) Method
 Risk of Soil De-compression
 Monitoring of Auger Cast Pile Installation
 Auger Cast Pile with Expander Body
 Displacement Auger Piles
 Vibrated Steel Piles with Expander Body
 Settlement-reducing Conical Concrete Nails
International DFI Conference – Stockholm 2014
2

3. Auger Cast Pile (CFA-pile)
Start of auger penetration
3

4. Auger Cast Pile (CFA-pile)
Auger penetration
Soil heave on ground surface
4

5. Auger Cast Pile (CFA-pile)
End of auger penetration
Competent layer has been reached
5

6. Auger Cast Pile (CFA-pile)
Start of grouting process
during auger extraction
6

7. Conventional Auger Cast Pile (CFA-pile)
7

8. Auger Cast Pile (CFA-pile)
8

9. Small and Large Stem Auger
9

10. Decompression due to
low penetration speed
Stiff layer
10

11. Decompression due to
high extraction speed
Risk of
necking
11

12. Risk of Soil Decompression during
Penetration
d l
D
vcrit Vd = v Dt
p
4
d2
VC +VD = v Dt
p
4
D2
VP = n l Dt
p
4
(D2
- d2
)
Volume of stem
Volume of stem and flight
Volume of pumped soil
vcrit = n l 1-
d2
D2
æ
è
ç
ö
ø
÷
Critical
penetration rate
n
12

13. Critical Penetration Speed –
Soil De-compression
vcrit = n l 1-
d2
D2
æ
è
ç
ö
ø
÷
13

14. Monitoring of Pile Installation
PENETATION
• Pushing force
• Penetration speed
• Torque
• Hydraulic
pressure
EXTRACTION
• Concrete
pressure
• Concrete volume
• Extraction speed
14

15. Illistration of Installation Record
15

16. 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
16

17. 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
17

18. Applications of Expander Body
Expander Body can
be combined with
conventional piling
methods:
• Vibrated steel tube
pile
• Continuous flight
auger pile (CFA)
18

19. Pressuremeter Test
19

20. Inflation of Expander Body
Expander Body
similar to
Pressure Meter
Test
Grout volume and
inflation pressure are
measured
20

21. 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
21

22. EB Grouting Recording
22

23. Grouting Pressure and Grouting
Volume, EB 600
23
Filling of EB
Expansion of EB
Soil displacement
Expansion
pressure

24. Post-grouting of Expander Body
Post-
grouted
Zone
Expander Body
shortens during
inflation
Inflation of
Expander
Body
Full
expansion
of Expander
Body
24

25. Auger Cast Pile with Expander Body
25

26. Advantages of CFE + EB
 Reduced pile length
 Known shape of pile base
 Recompression of soil at and below pile base
 Post-grouting of pile base avoids soil de-
compression
 Reduce pile shaft diameter
 Quality monitoring and control
26

27. Vibration Pile Test with Expander Body
Allermöhe, Germany
Expander
BodySteel tube piles
12 and 16 m long
27

28. Comparison Steel Tube Pile and
Expander Body Pile
Expander
Body
Steel tube
pile
Medium dense
sand
Loose sand
Organic layers
28

29. Comparison Steel Tube Pile and
Expander Body Pile
Expander
Body
Steel tube
pile
Medium dense
sand
Loose sand
Organic layers
Steel tube
pile
Expander
Body
29

30. Design of Bearing Capacity based
on CPT
Swedish Design
Recommendations
EB toe resistance:
Sand: sBase = 0.5 qc < 5MPa
Silt and clay: s Base = 1.0 qc
EB shaft resistance:
sShaft = 0.005 qc<50 kPa
D
qc
D
3D
30

31. Bearing Capacity from CPT Test
SHAFT
RESISTANCE
TOE
RESISTANCE
31

32. Installation of Vibrated EB Pile
32

33. Pile Test Loading
33

34. Steel Tube Pile vs. Expander Body
Pile length: 12 m
34

35. 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 base
 Post-grouting of pile base avoids soil de-
compression
 Quality monitoring and control
35

36. Gewerbehof Halle, Germany
36

37. Vibrated Conical Nails – Halle
Business Center, Germany
 Difficult ground conditions with variable fill
material
 Installation close to existing building
 Conical concrete nails vibrated to 9 m depth
 High driving frequency (38 Hz)
 Vibro-compaction at end of nail installation
 Load testing of concrete nail capacity
37

38. Settlement Reduction by vibrated
Concrete Nails
Alternative
foundation
solution to stone
columns or piles
38

39. Cone Penetration Test, CPT
Cone Resistance, MPa
Friction Ratio, %
Depth,m
Mixed fill
Dense
sand
Stiff clay
and
lignite
Medium
dense
sand
39

40. 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!
40

41. Load from Surface Foundation
Increased
confining
stress around
nails
Q
Load from
nails
Load from
footing
2
1
Load from
Footing
41

42. Load-sharing between Surface
Foundation and Concrete Nails
Increased
confining
stress around
nails
Q
Load from
nails
Load from
footing
Load from
Concrete
Nails
Load from
Footing
Factor of Safety of
Concrete Nails
Fs = 1.0
42

43. Ground Vibrations During Vibratory Pile
Driving
43

44. Variable Frequency Vibrator
NO ECCENTRIC MOMENT
DURING START-UP AND
SHUT-DOWN OF VIBRATOR
44

45. Variable Frequency Vibrator
STRONG VIBRATIONS
DURING DRIVING PHASE
45

46. 46
Avoids resonance peaks of
ground vibrations!
Resonance-free driving

47. Conical Concrete Nails
47

48. VIBRATION-
MONITORING
INSIDE BUILDING
ELECTRONIC PROCESS
CONTROL
VIBRATOR
MS100
VIBRATION
MONITORING
UNIT
CONCRETE
NAIL
48

49. Monitoring Resonance Compaction
Geophone
49

50. Installation of Concrete Nail
50

51. Frequency vs. Ground Response
0
2
4
6
8
10
12
14
16
18
5 10 15 20 25 30 35
FREEQUENCY, Hz
VERTICALPARTICLEVELOCITY,mm/s
Resonance
Frequency
Penetration
Frequency
Extraction
Frequency
Penetration
Frequency
Compaction
Frequency
51

52. 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, Hz
Depth, 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
52

53. Concrete Nails after Installation
53

54. Load Test of Concrete Nail and Steel
Tube Pile
54

55. 0
0,5
1
1,5
2
2,5
0 50 100 150 250 300 350
LOAD, kN
DEFORMATION,mm
Steel tube
Concrete Nail
Results of Loading Test
55

56. 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 compaction
 Conical shape provides high lateral
resistance near ground surface
 Known shape and material properties
56

57. Thank you!
57