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CONTENTS OF PRESENTATION

Design of Roadway Drainage Systems Using Geocomposite Drainage Layers by Barry R. Christopher, Ph.D., P.E. CONTENTS OF PRESENTATION. Water in Pavement Systems Design for Drainage Conventional Drainage Solutions Geocomposite Drainage Layer Solutions Drainage Requirements for Permeable Layer

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CONTENTS OF PRESENTATION

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  1. Design of Roadway Drainage SystemsUsing Geocomposite Drainage Layersby Barry R. Christopher, Ph.D., P.E.

  2. CONTENTS OF PRESENTATION • Water in Pavement Systems • Design for Drainage • Conventional Drainage Solutions • Geocomposite Drainage Layer Solutions • Drainage Requirements for Permeable Layer • Geocomposite Drainage Effectiveness • Cost-Benefit • Edge Drain and Outlet Requirements • Geotextile Filter Design • Specifications • Case Histories

  3. CONVENTIONAL FLEXIBLE PAVEMENTS Seal Coat Tack Coat Surface Course Prime Coat Binder Course Base Course Subbase Compacted Subgrade Natural Subgrade

  4. PAVEMENT DESIGN ENVIRONMENT TRAFFIC MATERIALS FAILURE CRITERIA STRUCTURAL MODEL MINIMUM THICKNESS, etc. STRUCTURAL DESIGN LIFE-CYCLECOST ANALYSIS CONSTRUCTION COSTS RIDEABILITY

  5. OPTIMUM INVESTMENT LEVEL TOTAL COST PRESENT WORTH FUTURE INVESTMENT Maint., Rehab., User, etc. OPTIMUM INITIAL COST RELIABILITY (pavement condition) 50 % 100 %

  6. CONSIDERATIONSIN PAVEMENT DESIGN • Continuous & Rapid Deterioration with Time • Repeated & Dynamic Loading • Different Load Magnitudes & Configurations • Traffic Distribution and Growth • Change Materials Properties & Characteristics • Drainage • Contamination of Road Materials

  7. FAILURE CRITERIA IN PAVEMENTS • RUTTING • FATIGUE CRACKING • THERMAL CRACKING • REFLECTION CRACKING • CONTAMINATION • DRAINAGE/ MOISTURE

  8. MECHANISTIC-EMPIRICAL FRAMEWORK IN THE 2002 PAVEMENT DESIGN GUIDE.

  9. ENVIRONMENTAL / CLIMATIC FACTORS • Temperature • Precipitation • Humidity • Depth to Water Table • Frost Susceptibility • Capillary rise Potential

  10. Water in the Pavement Structure Primary Cause of Distress

  11. Standing water in a pavement indicates low permeability and poor drainage

  12. Water in Pavement Systems AASHTO (1993) reports: • Water in the asphalt surface • Moisture damage, modulus reduction and loss of tensile strength • Saturation reduces dry modulus of the asphalt  30 % • Moisture in unbound aggregate base and subbase • Loss of stiffness  50 % • Water in asphalt-treated base • Modulus reduction of up to 30 percent • Increase erosion susceptibility of cement or lime treated bases • Saturated fine grained roadbed soil • Modulus reductions  50 %

  13. Effect of Moisture on Resilient Modulus Resilient Modulus MR, ksi 16 14 12 10 8 6 4 100% AASHTO - T99 2 95% AASHTO - T99 0 100 10 20 30 40 50 60 70 80 90 % Saturation, S

  14. Severity factor measures the relative damage between wet and dry periods For a pavement section with a moderate severity factor of 10, if 10% of time the pavement is approaching saturation, the pavement service life could be reduced by half. Ref. Cedergren, H.R. 1987, Drainage of highway and airfield pavements, Robert E Krieger Publishing Co, FL.

  15. Tire Tire Subgrade Subgrade DRAINAGE

  16. LOADED FLEXIBLE PAVEMENT Direction of Travel Free Water Wedge Deflection of Aggregate Base Deflection of Subgrade Hydrostatic Pressure

  17. CONTAMINATION / PUMPING HMA Base Subgrade

  18. AGGREGATE PENETRATION HMA Base Subgrade

  19. Under traffic loading, water and base material squirting up through joint in PCC pavement

  20. Direction of Traffic Hydrostatic Pressure Free Water orWater Jet Direction of Traffic Loaded PCC Pavement Water is Violently Displaced Carrying Suspended Fines

  21. JOINT DETERIORATION

  22. Water in Pavements Summary • Stripping in HMA • Loss of Subgrade Support • Reduction of Granular Layer Stiffness • Erosion of Cement-Treated Base Layers • Reduction in the Pavement Service Life If Base Is Saturated for Sometime • Debond between Layers

  23. HOW TO ADDRESS THE PROBLEM? • Pavement geometry (slopes and ditches) • Crack sealing • Treated Layer • Thicker Layers • Full Width • Subsurface Drainage 0.02 m/m 0.04 m/m HMA 1 : 6 Treated base 1 : 4 Aggregate base Subgrade

  24. Capillary Rise Through Permeable Surface Seepage Capillary Vapor Water Table Water Table

  25. Three important components for a good pavement design Drainage Drainage Drainage

  26. AASHTO Drainage Definitions Quality of Drainage Excellent Good Fair Poor Very Poor Water Removed Within* 2 Hours 1 Day 1 Week 1 Month Water will not Drain *Based on time to drain AASHTO Guide for Design of Pavement Structures, 1993

  27. Design for Drainage (AASHTO, 1993 Design Method) Structural Number (SN) for a pavement section is: SN = a1*d1 + a2*d2*m2 + a3*d3*m3 • a1 a2 a3 = layer coefficients for AC, BC and Sub base layers • d1, d2,d3 = their thickness • m2, m3 = drainage coefficients for the base and sub base layer • log10W18 = (ZR)(S0) + (9.36)(log10(SN+1) - 0.20 + log10[PSI/(4.2- 1.5)]/[0.40 + (1.094/(SN+1)5.19)] + (2.32)(log10MR) - 8.07

  28. AASHTO Guide for Design of Pavement Structures, 1993

  29. Quality of Drainage Percent of Time Pavement Structure is Exposed to Moisture Levels Approaching Saturation Less Than 1% 1-5% 5-15% Greater Than 25% Excellent 1.40-1.35 1.35-1.30 1.30-1.20 1.20 Good 1.35-1.25 1.25-1.15 1.15-1.00 1.00 Fair 1.25-1.15 1.15-1.05 1.00-0.80 0.80 Poor 1.15-1.05 1.05-0.80 0.80-0.60 0.60 Very Poor 1.05-0.95 0.95-0.75 0.75-0.40 0.40 Recommended Drainage Coefficient, mi, for Flexible Pavements AASHTO Guide for Design of Pavement Structures, 1993

  30. Rainfall Intensity for a 2-year, 1-hour Storm Event(FHWA, 1992)

  31. US Map with AASHTO Climatic Zones B C E F D B A

  32. WHEN IS THE OPTIMUM TIME TO MAINTAIN PAVEMENT? HOW ABOUT A BETTER DESIGN! CONDITION EXCLENT VERY GOOD GOOD FAIR POOR 75% of service life $1 not spend here... Will cost $4-10 here 40% quality loss AGE (years)

  33. Pavement Drainage Christopher and McGuffey, 1997, NCHRP Synthesis 239, “Pavement subsurface drainage systems”

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