1

Piled embankmentsConsidering the Basic Starting Points of the British Standard

Suzanne van Eekelen, Adam Bezuijen

September, 8th, 2008

2-10-2008versie 3.1 2

. Design reinforcementBS8006BS8006 wrongly interpretedModified BS8006. ComparisonWith each otherWith field measurements. Conclusions

BS8006 piled embankments

2

2-10-2008versie 3.1 3

pilesSoft subsoil

ditch

asphalt

foundation

sand

Granular materialgeogrid

1. Work floor

2. Piles

3. Pile caps

4. Reinforcement (geogrid)

5. Granular material for mattress

6. Rest of the embankment

7. Foundation and pavement / railroad

Piled embankments

2-10-2008versie 3.1 4

British Standard BS8006 from 19952008: New BS8006 is under construction

This presentation: only vertical load: 4 calculation steps

British Standard BS8006 (1995)

3

2-10-2008versie 3.1 5

3 dimensional: A A

C CC C

B BB B

1. Division into load parts

2-10-2008versie 3.1 6

Yes: C > 0 BS8006: No: C = 0

C C C C C C C

2. Support soft soil?

4

2-10-2008versie 3.1 7

B C B C B C B C B C B C B C B CB C B C B C B C B C B C B C B CB C B C B C B C B C B C B C B CB C B C B C B C B C B C B C B CB C B C B C B C B C B C B C B CB C B C B C B C B C B C B C B CB C B C B C B C B C B C B C B CB C B C B C B C B C B C B C B CB C B C B C B C B C B C B C B CB C B C B C B C B C B C B C B CB C B C B C B C B C B C B C B CB C B C B C B C B C B C B C B CB C B C B C B C B C B C B C B CB C

A

A

A

A AA

A A A

AAA

3. Assumption: concentrate B+C in line loads

2-10-2008versie 3.1 8

B C B C B C B C B C B C B C B C B C B C B C B C B C B

B C B C B C B C B C B C B C B C B C B C B C B C B C B

B C B C B C B C B C B C B C B C B C B C B C B C B C B

BCBCBCBCBCBCBCB

BCBCBCBCBCBCBCB

BCBCBCBCBCBCBCB

BCBCBCBCBCBCBCBA

A

A

A AA

A A A

AAA

3. Assumption: concentrate B+C in line loads

5

2-10-2008versie 3.1 9

3. Assumption: concentrate B+C in line loads

2-10-2008versie 3.1 10

3D BS 8006: 2D

Several authors assumed that BS8006 uses this

BS8006 (1995)

6

2-10-2008versie 3.1 11

line-load due to B + C

Line-load due to C

Tvert

WT

Beyond the scope of this presentation

4. From line load to tensile force

2-10-2008versie 3.1 12

AA

Marston (1913)

BB BBBB

AA

1. Division into load parts BS8006 (1995)

7

2-10-2008versie 3.1 13

p = 0

full arching: H = 1.4(s-a)

This gives a strange jump as H increases

WT = s ( H + p) X WT = 1.4 s (s-a) X

Partial arching Full arching

s a

1.4(s-a)AA AA

C CC C C C

BB BBBBH

s a

AA AA

C CC C C C

BB BBBB

lineload:

BS8006 (1995)

2-10-2008versie 3.1 14

NoYesSensitive forheightembankment andsurcharge load?

NoOnly for 2D approach line loadVerticalequilibrium?

H

Partial arching Full arching

s a

1.4(s-a)AA AA

C CC C C C

BB BBBBH

s a

AA AA

C CC C C C

BB BBBB

BS8006 (1995)

8

2-10-2008versie 3.1 15

Jump due to change from partial to full arching:traffic load disappears for full arching

0.00

40.00

80.00

120.00

160.00

200.00

0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00Height embankment (H)

Tens

ile fo

rce

in g

eosy

nthe

ticre

info

rcem

ent (

kN/m

')

parallel to road axisperpendicular to road axis

s = 1,0 m, a = 0,27 m, = 20 kN/m3,= 40,0o, asphalt + foundation =

9,87 kPa, traffic load 30 kPa, nopartial factors, end-bearing piles

H

a

s

,

BS8006 (1995)

2-10-2008versie 3.1 16

1 Division into load parts: Marston gives AVertical equilibrium gives B

2 No support soft soil gives C = 0

9

2-10-2008versie 3.1 17

Transition into line-loads:

BS 8006: 2D Improved BS 8006: 3D

Improving BS8006

2-10-2008versie 3.1 18

Partial arching

BS8006: Modified BS8006:WT = s ( H+p) X WT = 0.5 (s+a) ( H+p) X

Where22

222

asH

aCasX

c

s a

1.4(s-a)AA AA

C CC C C C

BB BBBBH

Improving BS8006

10

2-10-2008versie 3.1 19

Full arching

Surcharge load p = 0Load above H = 1,4(s-a) goes directly to the pilesCalculate pile load from vertical equilibrium

BS8006: Improved BS8006:WT = 1.4 s (s-a) X WT = 0.7 (s2-a2) X

s a

1.4(s-a)AA AA

C CC C C C

BB BBBB

H

Improving BS8006

2-10-2008versie 3.1 20

Kyoto Road field test (presentation this afternoon)

0000kNC loadon subsoil

88

24

48

5

BS8006

wronglyinter-

preted

61.48860.7kN/m’Tensileforce

142412kN/m’WT line-load ongrid

292924kNB loadon grid

5511kNA loadon pile

BS8006

Modified(3D)

BS8006

Original(2D)

EBGEO

no supportsoft soil

Comparison

11

2-10-2008versie 3.1 21

Kyoto Road field test (presentation this afternoon)

28

12

13

11

11

EBGEO

supportsoft soil

000022kNC loadon subsoil

88

24

48

5

BS8006

wronglyinter-

preted

61.48860.7-kN/m’Tensileforce

142412-kN/m’WT line-load ongrid

2929248kNB loadon grid

55115kNA loadon pile

BS8006

Modifiedfully 3D

BS8006

Original

EBGEO

no supportsoft soil

Averagemeasure-

ments

Kyoto Road

Comparison

2-10-2008versie 3.1 22

BS8006 is a rickety collection of inconsistent equations

•Vertical equilibrium is not satisfied

•BS8006 is basically a 2D approach

Modified BS8006

•gives prediction comparable with EBGEO (no support soft soil)

•Is fully 3D

For Kyoto Road support soft soil should be calculated with

Recommendation:

•Extend modified BS8006 for soft soil support

Conclusions consideration BS8006