Investigation into the use of the mechanistic empirical pavement design methodology for the design of a roadway pavement in Vergenoegen.

3.  Introduction
 Background
 Problem Statement
 Objectives
 Scope of project
 Methodology
 Pavement Design Approach
 Pavement Response Modeling
 Pavement Alternatives
 AASHTO 1993 Design
 AASHTO 2002 Evaluation
 Economic Evaluation
 Pavement Type Selection
 Pavement Structure
 Conclusion
 Recommendations

4. Purpose of Access Road:
1. Facilitate the movement of farmers to and from
the backlands
2. Access route to arable farm lands for cultivation
3. Low volume roadway
Geometric Configuration:
Length = 3 miles ( km)
Width = 22 ft ( m)

5. The Access Road in Vergenoegen
Look at this
road…I ain’t
going deh!

6. Location (6052’24.9’’N and 58021’51.30’’W)
Main Road
Access Road
Access Road

7. Condition (Wet Seasons)

8. Condition (Dry Seasons)

9. The statement of problem is to design a new
pavement structure for the access road in
Vergenoegen that could fulfill all the traffic and
environmental conditions while at the same
time being an economically viable structure.

10.  Quantify and characterize the loadings of the various
vehicles that uses the current facility
 Investigate and evaluate the potential of suitable pavement
alternatives for a cost effective alternative to
accommodate the present and future traffic loads on the
road
 Evaluate the potential advantages and disadvantages of
pavement alternatives
 Carry out life cycle cost analysis on the various pavement
alternatives to determine the most promising alternative
 Design proposal of a suitable access road based on the
most promising pavement alternative

11. Selection is limited to the most feasible
alternatives considered
Use of the AASHTO 1993 & AASHTO 2002
Guides for the Design of Pavement structures
Pavement distress is based on cracking and
rutting predictions as computed from the
pavement responses using the WinJULEA
software

12. 1 Inputs
Materials
Traffic
loadings
Environmen
tal data
2 Design
Alternatives
Layer
thickness
design
3
Evaluation
Technical
Economical
4 Pavement
selection
Most
feasible
alternative
5 Design
Proposal
Site
specific
conditions

13. AASHTO 1993 Guide for the Design
of Pavement Structures
AASHTO 2002 Guide for the
Mechanistic-Empirical Design of
Pavement Structures

15. Alternative 1 Flexible Pavement
Alternative 2 Semi Rigid Pavement
Alternative 3 Cement Treated Pavement

16. Design Traffic (Overall 18kips ESALs)
Graph Showing the Cumulative 18kips ESALs Over the 20 year Design Life
0
20000
40000
60000
80000
100000
120000
140000
160000
0 5 10 15 20
18kips ESAL
Time(years)
Cumulative 18kips ESAL
136, 584

17. Design Traffic for 20 Years
W18 = DDxDLxW18
DD = 50% (0.5) DL = 100% (1)
W18 = 136,584.6342 [18kips ESALs]
Therefore,
W18 = 0.5 x 1 x 136, 584.6342 18kips ESALs
W18 = 68, 293 [18kips ESAL]

18. Pavement Material Properties
Material Function CBR (%) Modulus (psi) Structural Layer
Coefficient
(Correlated from
AASHTO 93 )
Hot Mix Asphalt Surface Course 400,000 @ 68F 0.43
Crusher Run Base Course 60 0.12
Cement
Stabilized
Material
Base Course 830,000 @ 7days 0.22
White Sand Subbase Course 6 0.06
In-Situ Soil Subgrade 2 3000

19. Design Parameters
Reliability, R = 75%
Standard Deviation, So = 0.45
Initial Serviceability, pi = 4.5
Terminal Serviceability, pt = 2

20. Required Structural Number
Design Chart for Flexible Pavements used for Estimating the Structural
Number Required

21. Alternative 1 (Flexible Pavement)
Initial Structural Number 2.3
Layer Thickness Determination
Layer 1 Thickness, D1 (inch) 2
Layer 2 Thickness, D2 (inch) 6
Layer 3 Thickness, D3 (inch) 12
Final Structural Number 2.3
Asphalt Concrete
Ordinary White Sand
2in
6in
12in

22. Alternative 2 (Semi Rigid Pavement)
Initial Structural Number 2.3
Layer Thickness Determination
Layer 1 Thickness, D1 (inch) 2
Layer 2 Thickness, D2 (inch) 4
Layer 3 Thickness, D3 (inch) 12
Final Structural Number 2.5
Asphalt Concrete
Cement Treated
Base
Ordinary White
Sand
2in
4in
12in

23. Alternative 3 (Cement Treated Pavement)
Initial Structural Number 2.3
Layer Thickness Determination
Layer 1 Thickness, D1 (inch) 1
Layer 2 Thickness, D2 (inch) 7
Layer 3 Thickness, D3 (inch) 13
Final Structural Number 2.3
Chip Seal
Cement Treated
Base
Ordinary White
Sand
1in
7in
13in

24. Material Function Resilient Modulus
(psi)
Poisson’s Ratio
Hot Mix Asphalt Surface Course 400,000 0.25
Crusher Run Base Course 25,715 0.15
Cement Stabilized
Material
Base Course 830,000 0.35
White Sand Subbase Course 8,182 0.3
In-Situ Soil Subgrade 3000 0.2
Note:
All pavement layers were assumed to be fully bonded together at the
interfaces.

25. Traffic Loadings
9000 lbs9,000 lbs
18,000 lbs
Tire Radius = 6inches
Tire Pressure = 75psi
Fully Bonded Conditions

26. Bottom Up Cracking (HMA)
0
1
2
3
4
5
6
7
8
9
0 5 10 15 20
% of lane area cracked
Time (years)
Bottom Up Cracking Prediction vs Time
Chart Showing the % of Lane Area Cracked Over the Design Life for the
Flexible Pavement as a Result of Bottom Up Cracking

27. Top Down (Longitudinal) Cracking (HMA)
0
1000
2000
3000
4000
5000
6000
7000
8000
0 5 10 15 20
Feet/mile
Time (Years)
Longitudional Cracking Prediction vs Time
Chart Showing the Length of Longitudinal Cracking of the Flexible
Pavement Over the Design Life as a Result of Top Down Cracking

28. Rutting (Entire Pavement)
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0 5 10 15 20
Rutting (in)
Time(years)
Rutting vs Time
Chart Indicating Total Rutting of the Flexible Pavement Over the Design
Life

29. Bottom Up Cracking (HMA)
0
0.00005
0.0001
0.00015
0.0002
0.00025
0 5 10 15 20
% of lane cracked
Time (years)
Bottom Up Cracking vs Time
Chart Indicating Predicated % of Lane Area Cracked for the HMA Layer of
the Semi Rigid Pavement Over the Design Life as a Result of Bottom Up
Cracking

30. Top Down (Longitudinal) Cracking (HMA)
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
0 5 10 15 20
Feet/mile
Time (Years)
Longitudinal Cracking Vs Time
Chart Indicating Predicted Longitudinal Cracking of the HMA Layer for the
Semi Rigid Pavement over the Design Life as a Result of Top Down
Cracking

31. Rutting (HMA)
0
0.005
0.01
0.015
0.02
0 5 10 15 20
Rutting (in)
Time (years)
Rutting Vs Time
Chart Indicating Total Rutting in HMA Layer of the Semi Rigid Pavement
Over the Design Life

32. Flexural Cracking (CTB)
0
200
400
600
800
1000
1200
0 5 10 15 20
feet/500ft
Time(Years)
Fatigue Cracking vs Time
Chart Indicating Length of Cracking at the Bottom of the Cement
Treated Layer for the Semi Rigid Pavement Over the Design Life as a
Result of Fatigue Cracking

33. Flexural Cracking (CTB)
250
300
350
400
450
500
0 5 10 15 20
feet/500ft
Time(years)
Fatigue Cracking vs Time
Chart Indicating Length of cracks at the Bottom of the Cement Treated
Layer for the Cement Treated Pavement over the Design Life as a Result
of Fatigue Cracking

34. Pavement Alternatives Construction Cost/100m (G$)
Flexible Pavement 4, 601, 600
Semi Rigid Pavement 3, 153, 600
Cement Treated
Pavement
1, 661, 400
Cost of Construction for Pavement
Alternatives

35. Evaluation
Criteria
Construction
Cost
Ease of
Maintenance
Life Cycle
Cost
Failure
potential
Load
Distribution
Moisture
Sensitivity
Total
Weight 25 5 30 10 20 10 100
Flexible
Pavement
10 2 16 2 8 4 42
Semi Rigid
Pavement
16 3 20 4 12 5 60
CTB
Pavement
22 3.5 28 5 15 8 81.5
Decision Matrix for the Selection of the Most Suitable Pavement Alternative

37. Subgrade
Shoulder
Chip Seal
(1in) Cement
Treated
Layer (7in)
White
Sand
(13in)

38. The pavement alternatives evaluated ranged
from flexible, semi rigid to cement treated
pavements
Utilization of the AASHTO 2002 Guide for the
Design & Evaluation of Pavement Structures
The most viable pavement alternative is the
cement treated pavement since it is the most cost
effective pavement structure while optimizing the
level of service to the road users

39. Calibration of the empirical models to local
conditions to relate predicted distress to actual
distress occurrence
The use of the axle load spectra concept instead
of the 18kips ESAL concept
Modeling of the environmental conditions on the
performance of the pavement structures
(temperature & moisture)
Modeling of other distress modes such as
reflective cracking