Recent Development in Pile Instrumentation Technology for Driven, Jacked-in and Bored Cast-in-place Piles

1

Presented by : Lee Sieng Kai Glostrext Technology (S) Pte Ltd

www.glostrext.com.my

Recent Development in Pile Instrumentation Technology for Driven, Jacked-in and

Bored Cast-in-place Piles

Date : 20 August 2010

Venue : Engineering Auditorium, National University of Singapore

GEOTECHNICAL SEMINARGEOTECHNICAL SEMINARGEOTECHNICAL SEMINARGEOTECHNICAL SEMINAR

JOINTLY ORGANIZED BETWEEN GEOTECHNICAL SOCIETY OF SINGAPORE (GEOSS)

& CENTRE FOR SOFT GROUND ENGINEERING

• Introduction• The need and trends in pile instrumentation

• Review of Conventional Methods• Conventional pile instrumentation method for bored piles

• Conventional and Approximate methods for precast piles

• Development of Global Strain Extensometer Technology• Review of basic deformation measurement in pile by strain gauges and

extensometers

• Case Histories• Application on precast piles

• Application on bored piles

• Illustration of Instrumented Test Piles using Global Strain Extensometer Technique

• Discussion and Concluding Remarks• The benefits of using the Global Strain Extensometer technology

Outline

2

Introduction : basic static load test methods

Four basic pile load test methods (Joshi and Sharma, 1987)

1. Slow Maintained Load Test Method (SM Test or SMLT)

2. Quick Maintained Load Test Method (QM Test or QMLT)

3. Constant Rate of Penetration Test Method (CRP Test)

4. Swedish Cyclic Test Method (SC Test)

Main construction control for piles in early years:• Based on the measurement of set of each pile (driven); and

• A selected small number of non-instrumented static load tests to verify the Capacity and specified Load- Settlement requirement.

Introduction : basic static load test methods

Comparison of required time for various test methods (Fellenius, 1975)

Comparison of load-movement behavior for test methods (Fellenius, 1975)

3

2800t

2400t 4200t

2400t

Introduction : Examples of reaction load setup for axial compressive load tests on piles

• Millions (or billions?) of dollars are wasted every year due to over-designed (and under-provided!)foundations worldwide !

• There is tremendous needfor the static load test on preliminary test piles to be instrumented to measure and evaluate pile settlement, structural shortening /elongation, bearing capacity and transfer of load from the pile shaft and pile toe to the soil.

Introduction: The Need for Pile Instrumentation

SoftLayer

Competent Soil Strata

Existing GL

10.0 m

20.0 m

30.0 m

0.0 m

Ideal founding depth at 20.0 m

Case 1:

Ideal,

adequate,

safe and

economical

Case 2:

Over-

conservative,

not

economical

Case 3:

Under-

provided,

not safe

4

Introduction : Codes and Design Methods for Foundation Piles

According to Ken Fleming (1996): The basic parameters required for forecasting pile deformation under loads are :

(a) . Ultimate shaft load and its characteristics of transformation to the ground;

(b). Ultimate base load;

(c) . Stiffness of the soil below the pile base;

(d). Pile dimensions; and

(e) . Stiffness of the pile material.

CP4: 2003 7.5.3(b) Empirical correlation with SPT N-values using modified Meyerhof Equation are widely used in this region, where the ultimate bearing capacity of a pile in compression is given by:

Qu = Ks * Ns * As + Kb*(40Nb)*Ab

all the terms in equation as explained in CP4:2003

Circular on revised Singapore Standard on Code of Practice for Foundations CP4: 2003

5

• Sacrificial cast-in instrumentation method for cast-in-place bored piles:

• Vibrating wire strain gauges (recently fiber optic strain gauges) and mechanical tell-tales are normally installed and cast within the pile to allow for monitoring of axial loads and movements along the pile shaft.

• Similarly for grout-in-situ micropiles, barrettes etc..

Review of Conventional Methods : Cast-in-place piles Conventional Instrumented Test Pile

Apllied load measured by vw load cells

Pile head PTop Platform level

Verify and back- calculate Ec

Strain Gauges Lev. A

PB Tell-tale Extensometer 1

Strain Gauges Lev. B

P = ε (Ec Ac + Es As)or

P = ε (Ec Ac) PC follow normal terms

Strain Gauges Lev. C

PD Tell-tale Extensometer 2

Strain Gauges Lev. D

PE

Strain Gauges Lev. E

PF

Strain Gauges Lev. F Tell-tale Extensometer 3

Pile toe

Legend:

denotes Vibrating Wire Strain Gauges

denotes mechanical tell-tale extensometer

Review of Conventional Methods : Cast-in-place piles

• Some discussions/concerns on sacrificial cast-in instrumentation method for cast-in-place piles: • Generally this is the most commonly adopted method, most

engineers are familiar with it, and it yields satisfactory results for estimate of shaft & base resistances

• However, very often when there is difficulty in pile installation (concreting time, hole collapse……) or due to human problem, the instruments also get damaged! and that is the time…

Constraints include:• Long lead time.

• Strain gauges ~localised strain measurement….(long piles….)

• Tell-tales ~rod friction, bowing, eccentricity, reference beam movement….(long piles..)

• congestion of sleeved pipes/rods.

WHEN YOU NEED THEM

THE MOST…..

6

Review of Conventional Methods: Precast concrete piles

For precast driven / jack-in piles, the application of instrumented full-scale static load tests is far more challenging than their bored pile counterparts due to significant difference in method of pile installation.

Due to practical shortcoming of conventional instrumentation method and the lack of innovation in this area, instrumented full-scale static load tests are in fact rarely used in driven pile application in this region.

Therefore, the far lacking driven pile industry is long due for a better technology to revolutionize the methodology in the acquisition of design data in a more accurate and reliable way, to catch up with the evolution in the design methods.

Conventional Instrumentation Method for Prestressed Spun Concrete Piles

•Conventional instrumentation method for spun concrete piles piles:

• By incorporating high temperature-resistant strain gauges into the autoclaved heat-cured “spin-cast” production process of prestressed spun concrete piles

Strain Gauges Lev. A





Strain Gauges Lev. F

Existing Ground Level

Legends:

denotes high temperature - resistant

Strain Gauges

denotes Pile Joint

0

5

10

15

20

25

30

0 50 100 150N (blows/30cm)

Depth (m)

Clay

Sandy

Clay

Sandy

Silt

Spun Pile

Hollow annular space

Pile toe at 30.0 m depth

SI borehole log

(Pile head)

7

This method is extremely unpopular and difficult to be routinely applied in project sites due to the following constraints:

(a) High cost of these temperature-resistant strain gauges;

(b) Tremendous difficulties involved in coordinating the installation of the strain gauges into pile segments;

(c) Long lead-time is normally required for instrumentation works, as the instruments have to be pre-assembled and installed onto the high strength prestressing bar cage prior to autoclaved heat-cured ‘spin-cast’ production process of the piles; and

(d) Great uncertainty over the ability of the delicate instruments to withstand the stresses arising from pile production and driving processes.

Constraints of Conventional Method

• Due to the difficulties of using the conventional method, the engineering community for spun pile industry has been using an approximate instrumentation method for the past few decades, by installing either an instrumented reinforcement steel cage or an instrumented pipe, into the hollow core of spun piles followed by cement grout infilling

Strain GaugesvLev. A





Strain Gauges Lev. F

Existing Ground Level

Legends:

denotes Vibrating Wire Strain Gauges

denotes Pile Joint

Spun Pile

Cement Grout

Instrumented Pipe

0

5

10

15

20

25

30

0 50 100 150N (blows/30cm)

Depth (m)

Clay

Sandy

Clay

Sandy

Silt


SI borehole log

(Pile head)

Approximate Instrumentation Method for Prestressed Spun Concrete Piles

8

Typical installation process of spun pile instrumentation in Approximate Method


(i) (ii)

(iii) (iv)

Cement Grout Infill (Usually Grade 25)

Original

Wall

Thickness

(usually

Grade 80

Concrete

Instrumented Pipe (Instrumented Cage also

commonly used)

Section of instrumented spun pile after cement grout infilling in Approximate Method


9

The obvious shortcomings of this approximate method include:

(a) The infilling of cement grout substantially alters the structural properties of the piles, thus rendering them significantly different from the actual working spun piles, which are usually not grouted internally;

(b) The change in strain in the post-grouted core under the applied loading may not be the same as the change in strain in the prestressed concrete wall of the pile because of the different stiffness of the two materials of different mix, strength and age;

(c) Structural shortening measurement of the test piles are not representative of the actual working piles;

(d) Structural integrity of the original pile cannot be reliably ascertained, particularly performance of pile joints, during the static load test; and

(e) Significant time loss due to grout infilling and curing process, beside the environmental unfriendly nature of this method.

Shortcomings of Approximate Method

Glostrext inside

Arrangement of Global Strain Extensometer instrumentation approach for typical spun pile instrumentation application

50mm dia. Hole

Opening (Bottom

Plate) & 25mm Trench (Top Plate)

Min. 50mm thk Steel Plate

Min. 50mm thk pile top

steel plate (with 50mm

dia. centre hole)

Glostrext Anchor

Glostrext Sensor

Connecting Rod,

Hose & Signal Cable

Jacking System with Load Cell

12.5mm thk

Plywood

To Datalogger

Datalogger

Glostrext Sensor

Signal Cables, pressure hole

Min. 50mm thk Top

Steel Plate

Min. 50mm thk

Bottom Steel Plate

Development of Global Strain Extensometer Technology

Major breakthrough : Significant difference in the methodology adopted, from sacrificial cast-in method used in conventional technologies to a novel post-install approach

10

Glostrext inside

Completed improved prototype for application


Glostrext inside

Actual Global Strain Extensometer system for spun pile application


11

Glostrext inside

Laboratory Verification Tests


1200 mm

VWSGs Lev A: A1, A2, A3, A4

615 mm (Global Strain

Extensometer Sensor inside)

VWSGs Lev B: B1, B2, B3, B4

VWSGs Lev C: C1, C2, C3, C4

Glostrext inside


0

1000

2000

3000

4000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

Pile Top Load (kN )

Time (hours)

0

200

400

600

800

1000

1200

1400

1600

Change in Strain (microstrain)

S3-Global Strain Extensometer Technology

S3-Average VWSGs Lev A,B,C

Typical Results of Laboratory Verification Tests

Results and discussion will be published by UM (Prof. Faisal & Lee) at later stage

12

Basic concept

GaugeLength

GaugeLength

Accuracy of 0.1mm at best by DG/LVDT

Accuracy of 0.002mm or better

• Review of basic deformation measurement in pile by strain gauges and extensometers

•From a ‘strain measurement’ point of view, the strain gauge gives strain measurement over a very short gauge length while the extensometer gives strain measurement over a very long gauge length!

•Extensometer that measure strain over a very long gauge length may be viewed as a very large strain gauge or simply called Global Strain Extensometer �� (Glostrext)

BASIC PRINCIPLE OF MEASUREMENT INVOLVED

Global Strain Extensometer Instrumentation Scheme for Spun Piles

Schematic diagram of typical instrumented spun pile using Global Strain Extensometer technology

Anchored Lev. 6

Anchored Lev. 5

Anchored Lev. 4

Anchored Lev. 3

Anchored Lev. 2

Anchored Lev. 1

Anchored Lev. 0 Global Strain Gauge Lev. A Extensometer Lev. 1

Global Strain Gauge Lev. B

Global Strain Gauge Lev. C

Global Strain Gauge Lev. D

Global Strain Gauge Lev. E

Global Strain Gauge Lev. F

Extensometer Lev. 2

Extensometer Lev. 3

Extensometer Lev. 4

Extensometer Lev. 5

Extensometer Lev. 6

Existing GL

Legends:

denotes Glostrext anchored level

denotes Glostrext Sensor

denotes Pile Joint

Spun PileHollow annular space


Pressure supply,

regulator and manifold

Jacking System

and Reaction

Load Setup

DataloggerData collection

Load transferred (PAve) at mid-point of each anchored interval can be calculated as:

P = ε(Ec Ac )

where,

ε = average change in global strain gauge readings;

Ac = cross-sectional area of spun pile section;

Ec = concrete secant modulus in pile section

13

Global Strain Extensometer Scheme for RC Piles Description of Global Strain Extensometer (Glostrext) Instrumentation Technology for Reinforced Concrete Square Pile Static Load Tests

Instrumented RC Square Pile

Pile top load measured by VW Load Cell.

Anchored Lev. 0 Platform level

(Global Strain Gauge Lev. A)

Anchored Lev. 1 Extensometer Lev. 1

RC square pile

(Global Strain Gauge Lev. B)


(Global Strain Gauge Lev. C)


(Global Strain Gauge Lev. D)

steel pipe


(Global Strain Gauge Lev. E)

Glostrext Sensor


Glostrext Anchor (Global Strain Gauge Lev. F)


Pile toe

Legend:



Global Strain Extensometer Scheme for RC Piles Instrumented Micropile

(RL + m)

Reinforcement

Micropile

recess pipe

Pile toe at mdepth (RL m)

Legend:



Anchored Lev. 6

Glostrext Sensor 2


Extensometer Lev. 3


Global Strain Gauge Lev. A

Extensometer Lev. 1

Glostrext Sensor 11.0 m

2.0 m

0.0 m

Anchored Lev. 1

Anchored Lev. 0

Extensometer Lev. 6

Anchored Lev. 3

Glostrext Sensor 6Extensometer Lev. 5 Anchored Lev. 5

Global Strain Gauge Lev. D Glostrext Sensor 4

Extensometer Lev. 2 Anchored Lev. 2

Global Strain Gauge Lev. C Glostrext Sensor 3

Extensometer Lev. 4 Anchored Lev. 4

Global Strain Gauge Lev. E Glostrext Sensor 5

14

Global Strain Extensometer Scheme for Bored PilesGlobal Strain Extensometer Method for bored piles

Apllied load measured by vw load cells

Pile head

Instruments: Level No.

Global Strain A 2

Gauge B 2

C 2

D 2

E 2

F 2

Total= 12

Extensometer 1 2

2 2

3 2

4 2

5 2

6 2

Total= 12

Pile toe

Legend:

denotes GLOSTREXT anchored level

denotes GLOSTREXT Sensor


Anchored Lev. 0

Anchored Lev. 1

Anchored Lev. 2


Anchored Lev. 3


Anchored Lev. 4




Anchored Lev. 5

Anchored Lev. 6

Ext. Lev. 1

Ext. Lev. 2

Ext. Lev. 3

Ext. Lev. 4

Ext. Lev. 5

Ext. Lev. 6

Case Histories (Precast/Prestressed piles)

Recommended for reading :

1. Krishnan S. & Lee S.K., 2006. “A Novel Approach to the Performance Evaluation of Driven Prestressed Concrete Piles and Bored Cast-in-place Piles”. Proceedings of 10th International Conference on Piling and Deep Foundations, Amsterdam, pp 718-726

2. S.K. Lee, T.K. Lau, A.H. Tan, Faisal Hj. Ali, Y.W. Chong, 2007. “Recent Development in Pile Instrumentation Technology for Driven and Jacked-in Prestressed Spun Concrete Piles”, Proceedings of 16th South East Asian Geotechnical Conference, Kuala Lumpur, pp. 727-734.

3. Research Jacked-in Piles at Tuas South Avenue 2/5, 2009. CSCG-NUS (not yet published).

15

Applications of GLOSTREXT technology for Marine Piles:

1000mm Ø (with1400mm wall thickness) driven prestressed spun concrete pile GLOSTREXT instrumentation for 23 km long 2nd Penang Bridge, Malaysia, 2008.

Depth (m) Test Pile MLT-C (1000mm Ø)0.0 m RL +4.5m (Pile Head (H))

RL 0.00 m MLSD

Hollow core

Spun pile

Pile toe at 45.3 m depth (RL -40.8m)

Legend:



SI Borehole BH-16

45.0 m Anchored Lev. A-6

42.5m

Glostrext Sensor 2

11.5 m



Anchored Lev. A-5




Extensometer Lev. 3


Extensometer Lev. 2



Extensometer Lev. 1

Extensometer Lev. 6


1.5 m

Anchored Lev. A-1

Anchored Lev. A-0

Extensometer Lev. 5

43.75m Global Strain Gauge Lev. F Glostrext Sensor 6

39.0 m Anchored Lev. A-4 Extensometer Lev. 4

Global Strain Gauge Lev. E40.75m Glostrext Sensor 5

4.5 m

8

6

7

7

8

14

15

18

19

21

27

91

94

64

75

51

0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

32

34

36

38

40

42

44

46

48

0 25 50 75 100

SPT value, N

(blows/30cm)

Depth below pile top (m)

Seabed (RL-7.0m)

16.5 m

Seabed (RL-7.0m)

VS-1:

Peak=16kPa

Rem=5kPa

VS-2:

Peak=27kPa

Rem=10kPa

VS-3:

Peak=43kPa

Rem=13kPa

Silty Clay

Silty Sand


1000mm Ø (with1400mm wall thickness) driven prestressed spun concrete pile GLOSTREXT instrumentation for 23 km long 2nd Penang Bridge, Malaysia, 2008.

16


1000mm Ø (with1400mm wall thickness) driven prestressed spun concrete pile GLOSTREXT instrumentation for ICT Singapore.

Date of Pile Driving: 07-12-2009

Test Pile PTP1-BH7 (1000mm Ø)

Pile toe at 30.579 m depth (RL -26.779m)

Legend:



SI Borehole : BH7


29.3m



Anchored Lev. A-6

Glostrext Sensor 425.3 m Global Strain Gauge Lev. D


Extensometer Lev. 2


Extensometer Lev. 7



Extensometer Lev. 6

29.8m Global Strain Gauge Lev. G Glostrext Sensor 7

26.3 m Anchored Lev. A-4 Extensometer Lev. 4

Global Strain Gauge Lev. E27.3m Glostrext Sensor 5

0

0

43

42

100

111.1111111

136.3636364

142.8571429

136.3636364

125

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

0 50 100 150 200 250 300

Depth below pile top (m)

SPT value, N (blows/30cm)

Seabed (RL-9.433m)

Depth (m)

0.0 m

RL 0.00 m CD

RL +3.8m (Pile Head (H))

Global Strain Gauge Lev. A Glostrext Sensor 1

Anchored Lev. A-0

Extensometer Lev. 1

24.3m Anchored Lev. A-3 Extensometer Lev. 3

1.925 m

Hollow core

Spun pile

13.233m

0.3 m

Seabed (RL-9.433m)

VS-1:Peak=14kPa

Rem=4kPa

Marine Clay

VS-2:Peak=23kPa

Rem=8kPa

VS-3:Peak=40kPa

Rem=15kPa

OA

28.3m Anchored Lev. A-5 Extensometer Lev. 5

Global Strain Gauge Lev. F28.8m Glostrext Sensor 6

Applications of GLOSTREXT technology for RC Sq. Piles:

400mm x 400mm driven reinforced concrete square pile GLOSTREXT instrumentation at Damansara, Malaysia.

Instrumented Pile

(RL 40.0mm )


Legend:



SI Borehole : BH9

3

5

4

12

11

13

8

12

12

9

12

13

15

12

15

71

79

61

71

79

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

0 50 100 150 200

Depth below original ground level (m)


24.3m Anchored Lev. 6

Glostrext Sensor 24.8m


8.3 m Anchored Lev. 2




Extensometer Lev. 3


Extensometer Lev. 2



Extensometer Lev. 1

Extensometer Lev. 6


1.3 m

0.3 m

Anchored Lev. 1

Anchored Lev. A-0

23.8m Global Strain Gauge Lev. F Glostrext Sensor6

Glostrext Sensor 521.8 m Global Strain Gauge Lev. E

Extensometer Lev. 4 20.3 m Anchored Lev. 4

52mm Ø i.d.

steel pipe tohouse instruments

RC pile

23.3m Anchored Lev. 5 Extensometer Lev. 5

Clayey Sand

Sand

Sand Silt

Silty Sand

17

Case Histories (Bored Piles)

Recommended for reading :

1. H.M. A. Aziz & S.K. Lee, 2006. Application of Global Strain Extensometer (GLOSTREXT) Method for Instrumented Bored Piles in Malaysia. Proceedings of 10th International Conference on Piling and Deep Foundations, Amsterdam, pp 669-767

2. G&P Digest , Issue 1, July 2010. G&P Professionals Group.

18

Glostrext inside

Illustration of Test Results for Instrumented Test Pile using Global Strain Extensometer Technique

Application of Global Strain Extensometer Technique for 450mm Ø (with 80mm wall thickness) driven prestressed spun concrete pile for a reclaimed island petrochemical facilities project in Johor , Malaysia, 2008.

Test Pile No.

Nominal Diameter (mm)

Wall Thickness (mm)

9mm Ø Pre-stressing Bar Reinforcement

Driven Pile

Length (m)

Hydraulic Hammer Weight (tons)

Drop Height (mm)

Final Set (mm)

Date Driven

STP3 450 80 8 no. 47.25 9 400 3 21st Apr 08

19

Glostrext inside

Instrumentation levels for Instrumented Test Spun Pile STP3 (450 mm Ø) (with 80mm wall thickness)

Driven Pile length = 47.25m from Platform Level of RL 6.18 mCD

Instrumented Spun Pile

(RL 6.18m CD)

hollow core

spun pile

Bitumen coated


Legend:



SI Borehole : BH-STP3

9

12

14

16

18

11

8

2

0

2

3

4

10

13

15

9

15

16

19

22

26

27

20

25

22

25

18

17

19

16

19

25

30

136

167

273

250

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

0 50 100 150 200 250 300

Depth below original ground level (m)


47.2m Anchored Lev. 10

46.2m

Glostrext Sensor 24.7m



Anchored Lev. 9




Extensometer Lev. 4


Extensometer Lev. 3


Global Strain Gauge Lev. A Extensometer Lev. 1

Extensometer Lev. 10

Glostrext Sensor 10.7 m1.2 m

0.2 m

Anchored Lev. 1

Anchored Lev. A-0

46.7m Global Strain Gauge Lev. J Glostrext Sensor 10

Extensometer Lev. 9

Glostrext Sensor 737.7 m Global Strain Gauge Lev. G


8.2 m Anchored Lev. 2 Extensometer Lev. 2

Glostrext Sensor 314.2 m Global Strain Gauge Lev. C

Sand fill

Soft Marine Clay

VS-3:Peak=52kPa

VS-4:Peak=39kPa

VS-2:Peak=39kPa

VS-1:Peak=39kPa

VS-5:Peak=59kPa

VS-6:Peak=77kPa

Clayey Sand

Silty Sand

Rock

Silt

Glostrext Sensor 631.95 m Global Strain Gauge Lev. F



Glostrext Sensor 842.2 m Global Strain Gauge Lev. H


Glostrext Sensor 945.2 mGlobal Strain Gauge Lev. I

Instrumentation and maintained pile load test

Glostrext inside

Illustration of Test Results for Instrumented Spun Pile using Global Strain Extensometer Technique

Plot of pile top load versus pile top settlement, pile base settlement and total shortening for 450mm Ø Test Pile STP3

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

3000

0 5 10 15 20 25 30 35 40 45 50 55 60

Pile Top Load (kN )

Pile Top Settlement /Pile Base Settlement / Total Shortening (mm)

Pile Top Settlement Pile Base Settlement Total Shortening

20

Glostrext inside


Plot of pile top load versus pile shortening for various segments for 450mm Ø Test Pile STP3

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

3000

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0

Pile Top Load (kN )

Shortening (mm) of Pile

0.2m to 1.2m 1.2m to 8.2m 8.2m to 20.2m 20.2m to 24.2m

24.2m to 28.7m 28.7m to 35.2m 35.2m to 40.2m 40.2m to 44.2m

44.2m to 46.2m 46.2m to 47.2m

`

Glostrext inside


Plot of pile top load versus pile settlements at various depths for 450mm Ø Test Pile STP3

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

3000

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56

Pile Top Load (kN )

Pile Settlement (mm) at various depths

Piletop Settlement Sett at 1.2m Sett at 8.2m Sett at 20.2m

Sett at 24.2m Sett at 28.7m Sett at 35.2m Sett at 40.2m

Sett at 44.2m Sett at 46.2m Sett at 47.2m

`

21

Glostrext inside


Plot of back-calculated Concrete Modulus values, Ec, versus Measured Axial Strain at Level A using Global Strain Extensometer technique for 450mm Ø test pile STP3

y = -1.03E-03x + 4.45E+01

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800

Secant Modulus of concrete pile, Ec( kN/m

m2)

Measured Axial Strain ( x 10-6 ) at Level A

Glostrext inside


Load Distribution Curve for 450mm Ø test pile STP3

0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

32

34

36

38

40

42

44

46

48

0 300 600 900 1200 1500 1800 2100 2400 2700 3000

Depth below platform

level (m

)

Loads ( kN)

P= 205 kN P= 290 kN P= 563 kN P= 845 kN P= 1136 kN P= 1568 kN

P= 1780 kN P= 2004 kN P= 2221 kN P= 2440 kN P= 2650 kN P= 2871 kN

22

Glostrext inside


Load Transfer Characteristics during Loading stages for 450mm Ø test pile STP3

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

180

190

200

0 5 10 15 20 25 30 35 40 45 50 55 60

Mobilised Unit Shaft Friction ( kN/m

2)

Average Movement of Pile between soil stratum ( mm )

GL to Lev B

Lev B to Lev C

Lev C to Lev E

Lev E to Lev G

Lev G to Lev H

Lev H to Lev I

Lev I to Lev J

Glostrext inside


Plot of Mobilised Unit End Bearing versus Pile Base Settlement for 450mm Ø test pile STP3

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

7500

8000

0 5 10 15 20 25 30 35 40 45 50 55 60

Mobilised Unit End Bearing ( kN/m

2)

Pile Base Settlement ( mm )

23

Glostrext inside


Plot of Applied Pile Top Load, Total Shaft Resistance and Base Resistance versus Pile Top Settlement for 450mm Ø test pile STP3

0

300

600

900

1200

1500

1800

2100

2400

2700

3000

0 5 10 15 20 25 30 35 40 45 50 55 60

Load ( kN )

Pile Top Settlement (mm)

Q (Applied Load)

Total Shaft Resistance

Base Resistance

Glostrext inside


Plot of Pile Base Load over Applied Pile Top Load versus Pile Top Settlement for 450mm Ø test pile STP3

0

5

10

15

20

25

30

35

40

45

50

0 5 10 15 20 25 30 35 40 45 50 55 60

Pb/Ptop ( % )

Pile Top Settlement (mm)

24

Discussion and Concluding Remarks

Technology novelty and advantages

Global Strain Extensometer Technology

Costs

User Value

Value Innovation

Obvious COSTS benefits :

i) Significant cost/time saving;

ii) Environmental friendly (no grouting needed);

iii) Eliminates instrument damage risk.

Obvious VALUE benefits :

i) Flexibility to select instrumentation levels after pile installation;

ii) Reliable measurements over a larger and more representative sample;

iii) Routine instrumentation made viable

Discussion and Concluding Remarks

In summary, three distinct features of this method would especially appeal to geotechnical engineers:

(i) the method enables installation of instrumentation after pile installation and thus virtually eliminates the risk of instrument damage during pile production and installation;

(ii) the post-install nature of the method enables engineers to select instrumentation levels along the as-built depth of piles using pile installation records and site investigation data as guides;

(iii)the method reliably measures segmental shortening and strains over an entire section of the test pile during each loading step of a typical static load test and unlike conventional strain gauges which only provide localized strain measurements, it integrates individual strain measurements over a larger and more representative sample, thus making the test results more informative.

25

GEOTECHNICAL SEMINARGEOTECHNICAL SEMINARGEOTECHNICAL SEMINARGEOTECHNICAL SEMINAR

JOINTLY ORGANIZED BETWEEN GEOTECHNICAL SOCIETY OF SINGAPORE (GEOSS)

& CENTRE FOR SOFT GROUND ENGINEERING

Thank you

Documents

Recent Development in Pile Instrumentation Technology for Driven, Jacked-in and Bored Cast-in-place Piles