1-1 - climatic challenges in pavement design

8/7/2019 1-1 - Climatic Challenges in Pavement Design

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Climatic Challenges in Pavement Design

Joint Nordic/ Baltic Symposium on PavementDesign and Performance Indicators.

February 13 and 14 2008

Per Otto Aursand, NPRA, Northern Region

NVF 34NVF 34


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Climate & Transportation

R&D program evaluating the effect of climatechange on the road network and remedial actions

Norwegian Public Roads Administration

2007- 2010, cca 2,5 mill


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Main objective: Improve design, construction and

maintenance of the road network in order to adapt toclimate changes.i.e.

Evaluate and recommend measures necessary formaintaining both safety and accessibility in a changedclimate.


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Project tasks

1. Climate change and effects on road net - Survey

2. Data: collection, processing and storage

3. Flood and erosion prevention

4. Avalanches: snow-, soil-, flood slides, rock fall

5. Bearing capacity of roads

6. Consequences for winter operation7. Emergency plans and susceptibility


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Background

The road network is

influenced by climateconditions

Increased precipitation frequency andintensity

Milder winters

Warm summers in the south-eastern

areas Increased wind speeds and storm

frequencies


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Normal mean year temperature 1961-1990


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Estimated change in mean year temperature 1961-1990 2071-2100

(CICERO)

2,4 - 2,8 C


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Normal yearly precipitation 1961-1990


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Estimated change in yearly precipitation 1961-1990 2071-2100

(CICERO)

15 - 25 %


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Why is climate important in pavement design?

Properties

Climate

Stress

Lifetime


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Bearing capacity of roads

Temperature increase:

decreased pavement stiffnessaffects load distribution,changed frequency offreeze-thaw cycles

Precipitation increase:

higher ground water level,

higher infiltration of rainwater


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Consequences ofincreased persipitation

Increased water content in unboundmaterials

Reduced bearing capacity(deformation properties and load

distribution)

Increased deteriation (rutting androughness)

Moist pavementsurface

Increased wearof asphalt


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NEGATIVE consequences ofincreased

temperature Material properties of asphalt are closley dependent on temperature due

to reduced stiffness with increased temperature.

Reduced deformation properites

Reduced load distribution

Increased loading on sub-layers

A frozen road is very strong, and a reduced frozen period can lead toincreased deteriation

The number of freeze-thaw cycles will increase in some areas

Several spring-thaw weakening periodes during one singel winter

Melting of the upper part of the pavement reduced bearing capacity

Reduced frost index, but more critical where in the construction the icelenses from


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Variation of the bearing capacity during the year

SUMMERFALL SPRINGWINTER

Bear

ingcapacity


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Freeze-Thaw cyckles

Vanninn

hold

Freeze-thaw cycklesduring the winter Spring-thaw

weakening


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Scematic illustration of deteriation withand without climatic effects (Dor et al.2006)


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Examples of relative E-modulus for materials

during the spring thaw weakening period

Fines content


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Concequences in regions with increased

frequency of freeze-thaw cycles

Roads with poor materials high in the pavementwill have increased deteriation. (often low

volume roads)

For roads with good materials in the pavement,the concequences w ill be small (high volume

roads, main roads)

More periods with poor acessebility on gravelroads Increased need for maintenance.


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POSITIVE consequences ofincreased

temperature

The number of freeze-thaw cycles will be less

in some areas

Less frost heave in some regions

Reduced studded season

reduscedrutting caused by studs.


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Tasks in Project task 5 -Bearing capacity

of roads

5.1 How is materialparameters for road constructionmaterials affected by changed climate?

5.2 Consequences of changed climate for gravel roads

5.3 Consequences of changed climate for hard surface

roads

5.4 Pilotprojects


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Project task 5 Bearing capacity of

roads will be dealing with

Choice of models for calculating consequences (for a roadnetwork)

Calibration and abdoption of the model to Norwegianconditions

Calculation of changes in maintenance costs

Proposal for measures to cope with negativeconsequences

Pilotproject to show practical problems the climatechange can lead to, and nessesary adaptions to be made.

Effect of drainage on the lifetime of a road


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Evaluated models


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Examples of climatic data in AASTHO

2002


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Results


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Measures to cope with negative

effects of a changed climate Focus on bitumen-material

properties (stiffness, PmB)

Use ofnon-water-suseptible unboundmaterials

Improved drainage systemthat removes water fast andeffective from thepavement-structure


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AASTHO Design GuideRecommended E-modulus for base and sub-base depending of

the quality of the drainage system

0

50

100

150

200

250

300

350

400

450

500

0 5 10 15 20 25 30 35 40

Tid i % eksponert for vanninnhold som nrmer seg metning

E-modul

MPa

Svrt drlig

Drlig

BrukbarGod

Svrt god


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Material properties in a changed climate

Important properties for bitumen-materials:

- Good stability in high temperatures

- Resistance to water and salt Rutting

- Flexibility to variaation of bearing capacity and uneven frost heave.

Important properties for unbound materials:

- Fines content in materials where the water content is increased


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Thank you for your attention!

1-1 - climatic challenges in pavement design

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