Final year project ppt - The Future of Pavement Design

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

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Final year project ppt - The Future of Pavement Design

  1. 1.  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
  2. 2. 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)
  3. 3. The Access Road in Vergenoegen Look at this road…I ain’t going deh!
  4. 4. Location (6052’24.9’’N and 58021’51.30’’W) Main Road Access Road Access Road
  5. 5. Condition (Wet Seasons)
  6. 6. Condition (Dry Seasons)
  7. 7. 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.
  8. 8.  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
  9. 9. 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
  10. 10. 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
  11. 11. AASHTO 1993 Guide for the Design of Pavement Structures AASHTO 2002 Guide for the Mechanistic-Empirical Design of Pavement Structures
  12. 12. Alternative 1 Flexible Pavement Alternative 2 Semi Rigid Pavement Alternative 3 Cement Treated Pavement
  13. 13. 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
  14. 14. 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]
  15. 15. 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
  16. 16. Design Parameters Reliability, R = 75% Standard Deviation, So = 0.45 Initial Serviceability, pi = 4.5 Terminal Serviceability, pt = 2
  17. 17. Required Structural Number Design Chart for Flexible Pavements used for Estimating the Structural Number Required
  18. 18. 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
  19. 19. 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
  20. 20. 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
  21. 21. 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.
  22. 22. Traffic Loadings 9000 lbs9,000 lbs 18,000 lbs Tire Radius = 6inches Tire Pressure = 75psi Fully Bonded Conditions
  23. 23. 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
  24. 24. 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
  25. 25. 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
  26. 26. 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
  27. 27. 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
  28. 28. 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
  29. 29. 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
  30. 30. 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
  31. 31. 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
  32. 32. 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
  33. 33. Subgrade Shoulder Chip Seal (1in) Cement Treated Layer (7in) White Sand (13in)
  34. 34. 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
  35. 35. 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

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