Pavement Analysis
The effects of perpetual desing and Implementation of empirical pavement analysis. Bron [Artikel 1 J.P]
Different materials for pavement are based on
The climate
The country
The load
The circumstances
Climate => different effects on the pavement analyse
Use of the cement stabilised base
Flexible-composite
Perpetual pavement
Possible problems that needs to be considerd
Longitudinal cracking
Alligator cracking
Total rutting depth
International roughnes index
Life-cycle cost analysis
Influence of the asphalt layer on track information and rate of rutting
Test
Thicker asphalt layers (290mm)
Only 28% of the sections showed cracking and that was confined to the top layers
Thin asphalt layers (80mm)
Always full-depth cracking in the hole layer
Below a thickness of 180 mm
The thickness has a clear effect on the rate of rutting
The best pavement is with a asphalt layer of 300 mm thickness
The granular materials are used for conventional designs
The benefits and the disaventige of perpetual design
The initial cost are 20% higher than in other types of pavement
Benefits
The performance against surface distresses.
Perpetual paving avoids overstressing
Difference Rigid pavement VS Flexible Pavement
Layers
casted as 1 slab
multiple layers
Curing Time
24 hours
Lifespan
30 years
15 years
Joints
constructed in bays ---> joints needed
Laid constantly ---> no joints
composition
Binder ---> Cement
surface course
base course
subbase course
subgrade
Binder ---> Bitumen
surface course
base course
subgrade
Cost
Initial Cost
More
Less
Maintenace cost
Less
More
Modulus and thickness of the pavement surface layer from SASW tests
What is an SASW test?
"Spectral Analysis
of Surface Waves" test
Requirements for SASW
-Flat surface
-The width between impact and each sensor limits the search dept (width = 1,5 or 2 x depth is rule of thumb)
How does SASW work?
Surface wave testing uses the dispersive characteristics of surface waves to determine the variation of the shear wave velocity (stiffness) of layered systems with depth.
Why use SASW?
-Non-destructive
-Quick results
-Lot of different materials possible
-Up to 60m(!) deep
Asphalt properties
relationship between stiffness modulus and strain
The subgrade strain decreases as the asphalt thickness increases
elastic modulus
based on the recoverable strain under repeated loads
resilient modulus Mr
Mr= σd/εr
σd= deviator stress
εr= the strain
influence of stiffness modulus and temperature to strain
the stiffness modulus of asphalt mix is significantly influenced by pavement temperatures
when the temperature changes from 25°c to 50°c
the stiffness will shall decrease 10 fold (3783 Mpa -->319.7Mpa)
the asphalt strain will more than double
εv (275ms --> >600ms)
εr (80ms --> >180ms)
Realistic tire-pavement contact stresses into pavement analysis using nonlinear damage approach (Bron: Artikel 2 J.P)
Reliable pavement responses
A realistic tire-pavement interface
A accurate constituive relationschip of asphalt concrete
The different types of tires have different stresses at the pavement surface.
AC (Asphalt Concrete)
Highly complex composite material
Exhibiting recoverable and irrecoverable deformations
Important parameters to take into account:
Various applied loads
Tire inflation pressures
Vehicle speeds
Rolling conditions
The pavement dimension
Material properties
The vehicle loading condition
Speed from the user
Contact stresses caused by tires are influenced by
Including the tire inflation pressure
Vehicle speed
The condition of tire movement
Slip rations
Influence of the load contact geometry
The stress distribution influences
The residence times
The visco-elastic
Viscoplastic responces
The effect of the increase of non-uniform contact stresses on pavement surfaces
Pavement damage
Including topdown cracking
Near-surface cracking
Rutting
Solutions for stresses on flexible pavement response:
Vertical load shape
Distribution on pavement rutting potential
Effects of pavement thickness
Gravel base
optimal thickness 60cm
vertical deformation will decrease when layer gets thicker
Asphalt layer
vertical deformation will increase when layer gets thicker
Formula:
d=a(1 − b^h1), where a and b are both unknowns, d is the deformation and h is the thickness => non-linear!
usage of ground penetrating radar for pavement layer thickness analysis
radar
radar waves are transmitted then the amplitude and the time of each is collected
reliability
still needs a lot of testing
very promising technique
types of ground that are tested
asphalt
concrete
multilayer pavement
different layers are recognizable
radarwaves return an penetrate each junction between the layers