Download - S 3-3 Pavement Design in UK & Future Developments A_Collop

8/13/2019 S 3-3 Pavement Design in UK & Future Developments A_Collop

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Pavement design in the UKand future developments

Andy CollopProfessor of Civil EngineeringDirector of NTEC


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Outline

Standard UK pavement design

Foundation Upper pavement

Long Term Pavement Performance Model(LTPPM)

Summary


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UK pavement design

HA method for Trunk Roads & Motorways

Includes long-life designs (> 80 msa)

40 year design life (can be 20 years) Semi-empirical (analytical alternatives

allowed) Divided into foundation design and upper

pavement design


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Foundation design

Where does the foundation start?

Upperpavement

Pavement

foundation

SurfacingUpper Base

Lower Base

Subbase

Capping

Subgrade

HD26

HD25


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Philosophy

Based around the concept of a Surface

Modulus (half-space)


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Foundation classes

Class 1 50MPa Capping Only (< 20 msa)

Class 2 100MPa Granular Subbase (< 80 msa)

Class 3 200MPa Weak Cemented Subbase

(including hydraulically bound)

Class 4 400MPa Strong Cemented Subbase

(including hydraulically bound)


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HD25

Standard DesignsStandard Designs for Classes 2 and 3 (+

Class 1 for non HA roads); restrictedchoice of materials; CONSERVATIVE

Performance DesignsPerformance Designs for Classes 1 to 4;very wide choice of materials; much more

testing specified; MORE REALISTIC


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0

100

200

300

400

500

600

700

0 50 100 150

Subgrade Stiffness Modulus (MPa)

Th

ickness(m

m)

Capping, MCHW1 Series 600

Total Foundat ion thickness, Subbase Types 1,

2, 3 and R

Total Foundat ion thickness, Subbase Types

CBGMA or CBGMB, C3/4 or C5/6

CBR (%)

2 3 5 8 10 12 15 20 25

Class 2

Standard Class 2

(100MPa)


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Performance designs

Basis of Designs:

Three criteria

Surface deflection(relates to Surface

Modulus)

Subgrade Strain(relates to rutting)

Practical minimumthicknesses

40kN

Subbase

Capping

Subgrade

Surface

deflection

Subgrade

strain

10000MPa layer assumed 1.5m below

surface of subgrade

Circularcontact area,

radius 151mm


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Performance Class 2

(100MPa)

0

100

200

300

400

500

0 50 100 150Subgrade Stiffness Modulus (MPa)

SubbaseThickness(mm)

E(subbase) = 150MPa

E(subbase) = 200MPa

E(subbase) = 250MPa

Class 2

CBR (%)

2 3 5 8 10 12 15 20 25


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Performance Class 3

(200MPa)

0

100

200

300

400

500

0 50 100 150Subgrade Stiffness Modulus (MPa)

SubbaseThickness(mm)

E(subbase) = 500MPa

E(subbase) = 750MPa

E(subbase) = 1000MPa

E(subbase) = 2000MPa

Class 3

CBR (%)

2 3 5 8 10 12 15 20 25


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Stiffness measurement

Table 3.1 Equilibrium Subgrade CBR Estimation

High Water Table Low Water Table

Poor

ConstructionConditions

Average


Good


Poor


Average


Good


Soil PI

(%)

Thin Thick Thin Thick Thin Thick Thin Thick Thin Thick Thin Thick

Heavy Clay

Silty Clay

Sandy Clay

70

60

50

40

30

20

10

1.5

1.5

1.5

2

2.52.5

1.5

2

2

2

2.5

3.54

3.5

2

2

2

2.5

34

3

2

2

2.5

3

45

6

2

2

2

2.5

3.54.5

3.5

2

2.5

2.5

3

57

7

1.5

1.5

2

2.5

33

2.5

2

2

2

2.5

3.54

4

2

2

2

3

45

4.5

2

2

2.5

3

46

7

2

2

2

3

4

6

6

2.5

2.5

2.5

3.5

6

8

>8

Silt* - 1 1 1 1 2 2 1 1 2 2 2 2

Sand (poorly

graded)

Sand (well

graded)

Sandy Gravel

(well graded)

-

-

-

------------------------------------------------------------20------------------------------------------------------------

------------------------------------------------------------40------------------------------------------------------------

------------------------------------------------------------60------------------------------------------------------------

* estimated assuming some probability of material saturating

CBR

DCP

Springbox

Chart

FWD

Plate Loading

Triaxial


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Other layer combinations

Any combination of layers possible

The designer has to carry out a Multi-Layer Linear Elastic analysis to ensure

that the criteria are all satisfied Surface deflection

Subgrade strain Practical minimum thickness


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Outline





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Background

LTPPM developed with University of

Cambridge (Cebon)

Similar concept to MMOPP (Ullidtz)

Flexible (asphalt) pavements

Deterministic iterative procedure (profile &damage tracking)

Aggregate damage type of approach

V hi l

V hi l

V hi l


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LTPPM

Dynamicvehicle/axlegroup models

Primaryresponsecalculation

Damagecalculation

Feedbackmechanisms

Tyre forces

Time

Forc

e

Vehicle

simulation

Theoretical road damage

Distance along road

Damage

Road damage model

Lo g N

Log

Materialproperties

Time

Strain

Road strain at each point

Road model

Road response calculation

Distance

Strain

Influence

function

Environment

static

Surfaceruttingfedbackintovehiclemodel

Fatigue

damagefedbackinto

primaryresponsemo

del

Tyre forces

Time

Forc

e

Vehicle

simulation


Distance along road

Damage

Road damage model

Lo g N

Log

Materialproperties

Time

Strain


Road model


Distance

Strain

Influence

function

Environment

static


Fatigue

damagefedbackinto

primaryresponsemo

del

Tyre forces

Time

Forc

e

Vehicle

simulation


Distance along road

Damage

Road damage model

Lo g N

Log

Materialproperties

Time

Strain


Road model


Distance

Strain

Influence

function

Environment

static


Fatigue

damagefedbackinto

primaryresponsemo

del


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Example

Effect of road friendly suspensions

2 classes of pavement simulated

Major road (350mm asphalt)

Minor road (125mm asphalt)

Typical 3 layer flexible pavement structure

4oC to 18oC variation in MMAT

S rface profile e ol tion


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Surface profile evolution

(Major road)

-0.03

-0.02

-0.01

0

0.01

0.02

0.03

0 10 20 30 40 50 60 70 80 90 100

Distance / m

SurfacePro

fileElevation

/m

36 million load passes(10 years)

72 million load passes(20 years)

Initial profile

Rutting evolution


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Rutting evolution(Major road)

0

2

4

6

8

10

12

14

16

0 10 20 30 40 50 60 70 80

Load Passes (Million)

AverageR

utDepth/mm

'Critical' rut depth

Steel fleetRoad friendly fleet

20 years

Fatigue evolution


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Fatigue evolution(Major road)

0

0.5

1

1.5

2

2.5

3

3.5x10-3

0 10 20 30 40 50 60 70 80


95th

PercentileFatigueDamage

Steel fleet

Road friendly fleet

20 years


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Fatigue evolution


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Fatigue evolution(Minor road)

Steel fleet

Road friendly fleet

20 years

0

0.2

0.4

0.6

0.8

1

0 0.2 0.4 0.6 0.8 1 1.2


9

5thPercentile

FatigueDam

age

'Critical' fatigue damage


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Predictions

% increase in life changing from steel to

road friendly (air) suspensions

Major Minor

EC 24% 42%

LTPPM (3.5) 3% 39%

LTPPM (1) 0% 90%


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Outline




Summary


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Summary UK design

Foundation design + upper pavement

design

4 performance levels (surface modulus)

for foundations

More flexible designs (wider range of

materials)

Performance designs allowed


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Summary LTPPM (2)

Different modes of deterioration predicted

for different classes of pavement

Changing from steel to air increases life of

major road by


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Pavement design in the UKand future developments

Andy CollopProfessor of Civil EngineeringDirector of NTEC

Download - S 3-3 Pavement Design in UK & Future Developments A_Collop

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