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Mechanistic Empirical Pavement Design
- 1. Mechanistic- Mechanistic-Empirical Pavement Design P D i David P. Orr, PE Cornell Local Roads Program Co oc o ds og
- 2. NYS 180 - LaFargeville
- 3. NYS 180 - LaFargeville 800 AADT
- 4. Q: How thick are the asphalt and gravel layers? NYS 180 - L F LaFargeville ill 800 AADT
- 5. 17 ½ in.
- 6. ME Pavement Design Why roads fail Pavement design methods Mechanistic- Mechanistic Empirical M h i i -E i i l pavement d i design The need for seasons ME- ME-PDG
- 8. What is a road?
- 9. Road Structure Surface Base Subbase S bb Subgrade
- 10. Vehicle Loads Load Pavement Subgrade
- 11. Pavement Deflection Load Pavement Subgrade
- 12. Pavement Deflection Load T T Pavement C C C T Subgrade
- 14. Pavement Fatigue
- 15. Pavement Fatigue 45° 90° 180°
- 16. Pavement Failure? Potholes Alligator cracking Corrugations Edge raveling Rutting
- 17. Drainage
- 19. Pavement Design Methods Experience Catalog Empirical E ii l Mechanistic- Mechanistic-Empirical
- 20. Experience
- 21. NYSDOT Comprehensive Pavement Design Manual Black or white – Asphalt or PCC Mr – Subgrade resilient modulus ESALs ESAL – 50 year design life d i lif
- 22. AASHTO 1993 ⎡ ΔPSI ⎤ log10 ⎢ log10 W18 = ZR * So + 9.36* log10 (SN +1) − 0.20+ ⎣4.2 −1.5⎥ + 2.32* log M − 8.07 ⎦ 10 R 1094 0.40+ (SN +1)5.19
- 23. Mechanistic- Mechanistic-Empirical (M-E) (M- Strain Base Fatigue Failure Criteria T T V
- 24. Q: Which pavement design method do you use? Experience Catalog Empirical E ii l Mechanistic- Mechanistic-Empirical
- 26. Critical Fatigue Concepts Determine failure mode mechanistic Select a failure criteria empirical Develop failure D l a f il model? d l?
- 27. Fatigue Failure Criteria k2 ⎛ 1 ⎞ ⎛1⎞ k3 N f = k1 ⎜ ⎜ε ⎟ ⎜ ⎟ ⎟ ⎝E⎠ ⎝ cr ⎠ n(ε) ln ln(Nf)
- 28. Locations of Critical Strains Load T T T T C C C C T C C T V
- 29. Two Most Common Fatigue Failure Criteria Tensile strain in the surface (εt) cracking (ε Vertical strain on the subgrade (εv) rutting (ε
- 30. 3.9492 ⎛ ⎛E⎞ 1.281 1 ⎞ N f surface (106 ) = ⎜ 0.00432 C ⎜ ⎟ ⎟ ⎜ ⎝ E' ⎠ εt ⎟ ⎝ ⎠ Asphalt Horizontal Tensile Strain Criteria 10,000 10 000 strain) train (micros Average Coefficients K = 220.3 a = 4.260 1,000 b = -0.85 (Asph. Inst.) E 435 100 E' = 435,100 psi Horizontal St H 100 100 1,000 10,000 100,000 1,000,000 10,000,000 100,000,000 Number f Repetitions N b of R titi Asphalt Inst. TRL - 1 Average NAASRA Shell Denmark DTU
- 31. 3.902 ⎛ 1 ⎞ N f subgrade (10 ) = ⎜ 619.5 ⎜ 6 ⎟ ⎟ ⎝ εV ⎠ Subgrade Vertical Compressive Strain Criteria 10,000 ain) Vertical Strai (microstra 1,000 in Average Coefficients g V K = 619.5 a = 3.902 100 100 1,000 , 10,000 , 100,000 , 1,000,000 , , 10,000,000 , , 100,000,000 , , Number of Repetitions Denmark DTU Shell Average Nottingham Dorman & Metcalf TRL Asphalt Inst.
- 32. 3.902 ⎛ 1 ⎞ N f subgrade (10 ) = ⎜ 619.5 6 ⎜ ⎟ ⎟ ⎝ εV ⎠ ~4 ⎛ 1 ⎞ N f subgrade (10 ) ∝ ⎜ 6 ⎜ε ⎟⎟ ⎝ V⎠ ~4 N f subgrade (car ) ⎛ ε V (truck ⎞ ∝⎜ ⎜ ε (car ) ⎟ ⎟ N f subgrade (truck ) ⎝ V ⎠
- 33. Q: How many passes by a standard automobile are needed to equal the damage of one fully loaded 10-wheel 10- dump truck? 5,000- 5,000-10,000
- 34. Elastic Layer Theory Forward Calculation P, a Θ E1,η1,t1 Traffic P = Load R E2,η2,t2 a = Area Pavement layers Stress σX,Y,Z Ei = Modulus E3,η3,t3 Strain εX Y Z X,Y,Z ηi = Poisson’s ratio Poisson s Disp. δX,Y,Z ti = Thickness E4,η4,∞
- 35. Miner’s Hypothesis yp nf D = amount of f D= damage (%) Nf
- 36. Simple Pavement Asphalt 8 inches 158,000 psi Subbase 12 inches 36,400 36 400 psi Upper Subgrade 30 inches 14,700 psi Lower Subgrade ∞ 13,300 psi
- 37. ⎛ 1.281 1⎞ 3.9492 ESAL Load N f surface (10 ) = ⎜ 0.00432 C ⎛ E ⎟ ⎜ ⎞ 6 ⎟ ⎜ ⎝ E' ⎠ ⎟ εt ⎠ 9,000 9 000 lbs ⎝ Asphalt Horizontal Tensile Strain Criteria 10,000 10 000 strain) train (micros Average Coefficients K = 220.3 a = 4.260 1,000 b = -0.85 (Asph. Inst.) E 435 100 E' = 435,100 psi Horizontal St H 100 100 1,000 10,000 100,000 1,000,000 10,000,000 100,000,000 Number f Repetitions N b of R titi Asphalt Inst. TRL - 1 Average NAASRA Shell Denmark DTU
- 38. ESAL Loads ESAL Load Nf nf D= 9,000 lbs 9,420,000 Nf 5,000 AADT nf =4,710,000
- 39. Single Load nf 4,710,000 D= = = 50% N f 9,420,000
- 40. Miner’s Hypothesis yp n1 n2 ε D= + ≤1 (log scale)) N1 N 2 ε2 Load level 2 ε1 Load level 1 Nf2 Nf1 Nf (log scale)
- 41. Miner’s Hypothesis yp T ,season ,... , , nf D= Nf ∑ Di , j ,... i =1, j =1,.. , D ≤1
- 42. ME Design Traffic Seasons P = Load Annual a = Area Daily Pavement layers Long- Long-term Ei = Modulus Asphalt aging ηi = Poisson’s ratio Cracking ti = Thickness …
- 43. Backcalculation The process of converting i measured pavement deflections into layer moduli l d li
- 44. How Backcalculation 1. Select Works… Pavement layer / FWD Sensor 100 2. Use S d 2 U Seed Value Initial ction, mils deflection m 10 3. Select 2nd modulus Deflec 1 2nd deflection 4. Use FWD 0.1 deflection to 1,000 10,000 100,000 estimate Modulus, psi M d l i modulus
- 45. The Need for Seasons
- 46. Seasonal Changes Frozen Rapid drainage Refreezing Thawing Slow recovery Asphalt Surface and Base Granular Subbase Weather Affected Subgrade Subgrade Jan. Dec.
- 47. Seasonal Models Modulus s J A J O Date Subbase Seasonal Subgrade Subgrade
- 48. Effect of Changing Season Lengths Initial inputs 7 days of Spring thaw Nf = 660 000 ESAL 660,000 ESALs Increase Spring-thaw from 7 to 28 days Spring- Nf = 490 000 ESALs 490,000 26.2% decrease in lifespan
- 49. Number of Days of Thaw
- 50. Seasonal Response Techniques Calculate average annual response Detailed hourly calculations Representative year R i
- 51. AASHTO Pavement Design Guide −2.32 u f = 1.18 x10 xM R 8 uf - Relative damage, damage MR - Roadbed soil resilient modulus (psi)
- 52. Q: Which layers in the pavement change seasonally? All of them dulus Mod J A J O Date Subbase Seasonal Subgrade Subgrade
- 53. Expanded Seasonal Pavement Moduli Models
- 54. FWD Testing Sites Phase I Ph Phase II Frost Depth > 1,100 mm Frost Depth < 600 mm Plasticity Index > 12
- 55. ME- ME-PDG
- 56. Critical Variables Traffic Need to account for overloads Weather Daily changes Seasonality Pavement structure & materials Thickness Quality of construction Long- Long-term changes All variables
- 57. M-E Design Guide
- 59. Questions
- 60. Q: What are the primary 2 failure modes for asphalt pavement? Tensile strain in the surface Fatigue cracking Compressive strain on the subgrade C i i h b d Subgrade rutting
- 61. Q: When is a pavement the strongest? Winter
- 62. Q: When is a pavement the weakest? Spring thaw
- 63. Q: Backcalculation should be used on all pavements? No
- 64. Thank You David Orr Senior Engineer Cornell L l R d P C ll Local Roads Program 416 Riley-Robb Hall Riley- Ithaca, NY 14853 Ithaca 607-255- 607-255-8033 dpo3@cornell.edu p @ www.clrp.cornell.edu