capacity of CFA piles for Seaford Australian Small Bridges

Estimated versus measured capacity of CFA piles for Seaford Road bridges, MelbourneCillian Mc Colgan

Associate Geotechnical Engineer, WSP – Melbourne, Australia

9th Australian Small Bridges Conference 2019Queensland, Australia

Overview

1. Background

2. Geotechnical model & design parameters

3. Axial capacity and pile design

4. Construction validation

5. Analysis of pile test results

6. Conclusions

Project Overview

Southern Program Alliance

• Removal of 4 level crossings in Melbourne’s South East for Initial Works Package

• Part of the Victorian Government’s AU$8.3 billion project

• Improve traffic flow

• Improve walkability within community

• Create safer communities

Melbourne CBD

Approx. 37 km

– Two parallel U trough girder bridges

– Combined span > 110m

– Grade separates Seaford Road with the Frankston Rail Line

– Bridges founded on Continuous Flight Auger (CFA) Piles

Seaford Road Bridges

9th Australian Small Bridges Conference 2019

Background

4



Background

5



Background

6

Geological Unit and ID Material Description Consistency Depth to top

(m bgl)

Unit 1 Fill Shallow fill associated

with rail formation

N/A 0.0

Unit 2 2A Quaternary Sands Dune Sands Medium

Dense

0.0 – 1.0

2B Swamp deposits Sands with

occasional layers of

compressible back

swamp materials

Loose 2.9 – 6.5

Unit 3 3A Brighton Group

(Sandringham

Sandstone)

Sandy Clay Stiff to Hard 4.1 – 8.0

3B Clayey Sand,

occasionally

cemented

Medium

Dense to

Very Dense

10.0 – 16.5

Unit 4 Gellibrand Marl Stiff to Very Stiff Stiff to Very

Stiff

19.0 – 22.6

Geotechnical Model


– Ten geotechnical boreholes (maximum depth of 46.85m below existing ground level)

– Thirteen Cone Penetration Tests (CPT)

Geotechnical

Model and

Design

Parameters

7

Geotechnical Long Section – Seaford Road Bridge


Geotechnical

Model and

Design

Parameters

8

Geotechnical Long Section – Pedestrian Underpass


Geotechnical

Model and

Design

Parameters

9

In-situ Test Results


Geotechnical

Model and

Design

Parameters

10

-22

-20

-18

-16

-14

-12

-10

-8

-6

-4

-2

0

0 10 20 30 40 50 60

RL

(m

AH

D)

SPT N1,60

Unit 2A Unit 2C Unit 3A Unit 3B Unit 4

Geological Unit and ID

Unit 2 2A Quaternary Sands

2B Swamp deposits

Unit 3 3A Brighton Group

(Sandringham

Sandstone)3B

Unit 4 Gellibrand Marl

Unit 2B

Geological Unit and ID Undrained Shear

Strength, Su (kPa)

Effective Cohesion,

c’ (kPa)

Effective

Friction

Angle, ’

(Degrees)

Ultimate

skin

Friction, fs

(kPa)

Ultimate

End

Bearing, fb

(kPa)

Unit 2 2AN/A 0

29° – 32° 15 - 24 N/A

2B

N/A 0

28° – 33° 4 - 32 N/A

Unit 3 3A 40 - 200 - - 16 - 65 1100 - 3600

3B

N/A 0 30° – 36° 16 - 65

1100 - 3600

Unit 4125 - 175 0

28° – 33° 39 - 43 700 – 1200

Geotechnical design parameters


– Skin friction after O’Neill and Reese (1999)

– End Bearing after Flemming et al (2009) for cohesive and Berezanatzev (1961) for granular

– Limiting values after Decourt (1995)

Geotechnical

Model and

Design

Parameters

11

BRIDGE Foundation

Location

Pile Diameter

(mm)

Required

Ultimate

Capacity

at Pile

Head1

(kN)

Pile

Length

(m)

Founding

Material

PEDESTRIAN

ACCESS BRIDGE

Abutment A 1050 3740 20.0 Stiff Clay

Abutment B 1050 3740 19.5 Very Stiff

Clay

SEAFORD ROAD

BRIDGE

Abutment C 1050 3740 19.0 Very Stiff

Clay

Pier 1A/1B 1050 3650 18.0 Very Stiff

to Hard

Clay

Pier 2A/2B 1050 3650 19.5 Stiff to

Very Stiff

Clay

Abutment D 1050 3740 19.0 Very Stiff

Clay

Pile Design


Pile Design

12

Pile Design – Seaford Road Bridge


Pile Design

13

APPROXIMATE PILE

TOE LEVELS

Pile Design – Pedestrian Underpass


Pile Design

14

APPROXIMATE PILE

TOE LEVELS

Pile Installation Records


Construction

Validation

15

– LB28 Rig with Jean Lutz Software

– Unreliable

– No clear correlation

– No clear evidence of weak layers

– General increase in resistance versus depth

– Larger as built pile diameter

Inspecting Pile Cuttings


Construction

Validation

16

– Soil mixing during drilling

– Soil disturbance during drilling

– Toe validated after pile poured

– Reliance on validation of CFA piles is both impractical and unreliable for floating piles

– Rely on boreholes and design appropriately considering variability

Dynamic Pile Testing


Construction

Validation

17

– 1 Pile per pile group tested in accordance with VicRoads Specification 607

– Geotech’s custom built rig with 12T drop hammer

– Minimum 6 days of set up

– Piles tested at modest energy, that is, energy that was determined by the testing contractor to be sufficient to achieve the nominated test loads

Dynamic Pile Testing Results


Construction

Validation

18

Bridge Foundation

Location

Estimated

Pile

Capacity

(kN)

Measured

Pile

Capacity

(kN)

Estimated

Shaft

Force

(kN)

Measure

d Shaft

Force

(kN)

Estimated End

Bearing Force

(kN)

Measured End

Bearing Force

(kN)

Abutment A - P09 3746 9575 3221 6112 925 3463

Abutment B - P04 3751 6487 2934 5188 1195 1299

Abutment C - P03 3741 9303 2764 6273 1360 3030

Pier 1A - P01 3651 8869 2653 7138 1359 1731

Pier 1B - P01 3651 7746 2653 6231 1359 1515

Pier 2A - P02 3641 7513 3206 5781 820 1731

Pier 2B - PP08 3641 7336 3206 5605 820 1731

Abutment D – P04 3745 7323 1927 5592 2098 1731

Other DynamicTesting – Approach Embankments


Construction

Validation

19

Bridge approach embankment rigid inclusions to address potential differential settlement where no preload time was available

Other DynamicTesting – Utility Protection Slab


Construction

Validation

20

Other Dynamic Test Results


Construction

Validation

21

Rigid Inclusions Location Measured Pile

Capacity (kN)

Diameter (mm) Length

(m)

Measured

Shaft Force

(kN)

Measured End

Bearing Force

(kN)

AD87 2427 500 8.6 1691 736

AB32 1592 500 8.6 840 742

AA06 1989 500 10.6 1351 638

PN59 1200 500 8.4 660 540

PN70 4879 600 17.0 3041 1838

PN61 4520 600 17.0 3177 1343

PN55 5641 600 17.0 3945 1696

Test Pile Abutment A 1050 3472 9 1740 1732

Test Pile Abutment C 1050 9040 14 3412 5628

Other Dynamic Test Results – Destructive Tests

9th Australian Small Bridges Conference

2019

Construction

Validation

22

Rigid Inclusions Location Measured Pile

Capacity (kN)

Diameter (mm) Length

(m)

Measured

Shaft Force

(kN)

Measured End

Bearing Force

(kN)

Test Pile Abutment A 3472 1050 9.0 1740 1732

Test Pile Abutment C 9040 1050 14.0 3412 5628

– Test Pile at Abutment A Founded in unit 3A Brighton Group Sand

– Test Pile at Abutment C Founded in unit 3B Brighton Group Clay

– Test Pile at Abutment A not successful due to issues with cold joint in the pile upstand

Analysis of Pile Test Results – Shaft Friction


Analysis of Pile

Test Data

23

-22

-20

-18

-16

-14

-12

-10

-8

-6

-4

-2

0

0 40 80 120 160 200

RL

(m

AH

D)

Unit Skin Friction (kPa)

Unit 2 Unit 3A Unit 3B Unit 4

Unit N1,60 Shaft Friction (kPa) Correlation

Range Mean Range Mean

Unit 2

Sand

L – MD

0 –

43

15 50 –

80

65 Fs =

4.3*N1,60Unit 3A

Sandy Clay

St - Hrd

10 –

71

23 50 -

120

80 Fs =

3.5*N1,60

Unit 3B

Clayey

Sand

MD - VD

0 -

70

33 80 -

150

100 Fs =

3.0*N1,60

Unit 4

Silt/Clay

Vst - Hrd

10 –

65

21 50 -

150

100 Fs =

4.7*N1,60

-22

-20

-18

-16

-14

-12

-10

-8

-6

-4

-2

0

0 10 20 30 40 50 60 70

RL

(m

AH

D)

Seaford - N1(60) vs RL (m AHD)

Unit 2A Unit 2C Unit 3A

Unit 3B Unit 4

Analysis of Pile Test Results – End Bearing


24

Pile ID End bearing Unit N1,60 at pile toe1 Measured end bearing (kPa) Correlation with N

Ab A – P09 Unit 4 15 4000 267

Ab B – P04 Unit 4 18 1500 83

Ab C - P03 Unit 4 22 3500 159

Pier 1A – P01 Unit 4 36 2000 56

Pier 1B – P01 Unit 4 36 1750 49

Pier 2A – P02 Unit 4 13 2000 154

Pier 2B – PP08 Unit 4 13 2000 154

AbD Unit 4 16 2000 125

Averages for Unit 4 - Silt/Clay ,Vst - Hrd 21 2344 111

Test Pile C Unit 3A 26 2000 77

AD87 Unit 3A 18 3750 208

AB32 Unit 3A 18 3750 208

AA06 Unit 3A 68 3680 54

PN59 Unit 3A 27 6000 222

Averages for Unit 3A Sandy Clay, St - Hrd 33 4295 131

Test pile A Unit 3B 29 6500 224

PN70 Unit 3B 30 6500 217

PN61 Unit 3B 30 4750 158

PN55 Unit 3B 30 6000 200

Averages for Unit 3B Clayey Sand, MD -

VD 30 5938 200

Analysis of Pile

Test Data

20

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

180

190

200

0 50 100 150 200 250 300 350 400

Unit

Skin

Fri

ctio

n (

kP

a)

Applied Energy (kJ)

All Units

AA-09 - U2 AB-04 - U2 AC-03 - U2 AD-04 - U2 CMC-AA-06 - U2 CMC-AB-32 - U2CMC-PN-59 - U2 CMC-AD-87 - U2 CMC-PN-55 - U2 CMC-PN-61 - U2 CMC-PN-70 - U2 P1-A1 - U2P1-B1 - U2 P2-A2 - U2 P2-B8 - U2 TP-AA - U2 TP-AC - U2 AA-09 - U3AAB-04 - U3A AC-03 - U3A AD-04 - U3A CMC-AA-06 - U3A CMC-AD-87 - U3A CMC-PN-55 - U3ACMC-PN-61 - U3A CMC-PN-70 - U3A P1-A1 - U3A P1-B1 - U3A P2-A2 - U3A P2-B8 - U3ATP-AA - U3A TP-AC - U3A AB-04 - U3B AA-09 - U3B AC-03 - U3B AD-04 - U3BCMC-PN-55 - U3B CMC-PN-61 - U3B CMC-PN-70 - U3B P1-A1 - U3B P1-B1 - U3B P2-A2 - U3BP2-B8 - U3B TP-AA - U3B AA-09 - U4 AC-03 - U4 AD-04 - U4 AB-04 - U4P1-A1- U4 P1-B1 - U4 P2-A2 - U4 P2-B8 - U4 AA-09 - U2 AB-04 - U2AC-03 - U2 AD-04 - U2 CMC-AA-06 - U2 CMC-AB-32 - U2 CMC-PN-59 - U2 CMC-AD-87 - U2CMC-PN-55 - U2 CMC-PN-61 - U2 CMC-PN-70 - U2 P1-A1 - U2 P1-B1 - U2 P2-A2 - U2P2-B8 - U2 TP-AA - U2 TP-AC - U2 AA-09 - U3A AB-04 - U3A AC-03 - U3A

25

Analysis of Pile Test Results – Shaft Friction vs Energy


Analysis of Pile

Test Data

No apparent increase with higher energyMajority of data in this region

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

0 50 100 150 200 250 300 350 400

Unit

End

Bea

ring(k

Pa)

Applied Energy (kJ)

All Units

AA-09 - U4 AB-04 - U4 AC-03 - U4 AD-04 - U4 P1-A1- U4 P1-B1 - U4 P2-A2 - U4 P2-B8 - U4

TP-AA - U3B TP-AC - U3A CMC-AA-06 - U3A CMC-AD-87 - U3A CMC-PN-55 - U3B CMC-PN-61 - U3B CMC-PN-70 - U3B

26

Analysis of Pile Test Results – End Bearing vs Energy

Rigid inclusions capable of

mobilising more end bearing at

lower energy

Destructive test

demonstrates higher end

bearing for 1050 pile


Analysis of Pile Test

Data

27

Conclusions


Conclusions

– Conventional design methods can be overly conservative for pile design in the Brighton Group and Gellibrand Marl Units

– The Brighton Group and Gellibrand Marl Units both displayed skin friction far greater than conventional design would suggest

– The Brighton Group units showed a similar trend for end bearing though the data to support this is not as comprehensive as that for shaft friction and it is limited to smaller diameter piles

– There is likely more end bearing capacity available in the Gellibrand Marl than was encountered at Seaford bridge

– Potential to prove greater capacities with destructive testing

28

Caution


Conclusions

– When selecting pile test data as a design basis this must be taken in the context of the consequence of a pile test failing. Where consequence is high conventional approaches while conservative, may be appropriate as they provide confidence that tests will pass

– Where consequence of a test failing can be managed a less conservative design approach could be adopted provided risks are understood by contractor and contingencies are in place

– Contingencies can include

– Mobilise larger hammer

– More piles at shallow depth leaving the option to deepen

– Make an increased allowance for pile set up i.e. > 7 days

– If you have paid to mobilise a test rig – hit the piles hard and contribute to a database of testing that the infrastructure industry needs

29

The Future?


Conclusions

30

Acknowledgements


Conclusions

The authors would like to thank the Level Crossing Removal Project and the

Southern Program Alliance for permission to present this work.

Documents

capacity of CFA piles for Seaford Australian Small Bridges