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PAVEMENT DESIGN

Design of Roadway Drainage Systems Using Geocomposite Drainage Layers by Barry R. Christopher, Ph.D., P.E. PAVEMENT DESIGN. ENVIRONMENT. TRAFFIC. MATERIALS. FAILURE CRITERIA. STRUCTURAL MODEL. MINIMUM THICKNESS, etc. STRUCTURAL DESIGN. LIFE-CYCLE COST ANALYSIS. CONSTRUCTION COSTS.

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PAVEMENT DESIGN

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

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

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

  4. 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

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

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

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

  8. Water in the Pavement Structure Primary Cause of Distress

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

  10. Tire Tire Subgrade Subgrade DRAINAGE

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

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

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

  14. JOINT DETERIORATION

  15. 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

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

  17. 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

  18. Crushed Outlet Clogged Outlet

  19. Time To Drain • For two lane road - Lane width = 24 ft, Slope = 0.01 Base k time to drain Quality OGB 1000 ft/day 2 hrs to drain Excellent DGAB 1 ft/day 1 week Fair DGAB w/ fines 0.1 ft/day 1 month Poor Reality no drains does not drain Very Poor

  20. Geocomposite Drain Requirements • Sufficient stiffness to support traffic without significant deformation under dynamic loading • Inflow capacity > infiltration from adjacent layers • Sufficient transmissivity to rapidly drain the pavement section and prevent saturation of the base • Sufficient air voids within geo-composite to provide a capillary break

  21. Drainage Geocomposite - Important Properties • Transmissivity = 4500 ft2/day (0.005 m2/sec) • Estimated Discharge: 30 ft3/day /ft • Creep Resistance under high Loads • Long-term Resistance to Compression • Stability Traffic Loads = Univ. of Illinois Study • Effective Porosity = 0.7 • Geotextile Filtration Requirements

  22. Design Manual for Roadway Geocomposite Underdrain Systems: SCOPE • Design guidance for a new alternative drainage method • Horizontal geocomposite drainage layer tied directly and continuously into an edge drain system. • RoaDrain™ 100-2 by the Tenax Corporation) • Current AASHTO and Corps of Engineers pavement design codes • Application • Used directly to replace drainable aggregate layers in rigid or flexible pavement systems, or • Enhance the drainage of dense graded aggregate layers often used in flexible and rigid pavement systems.

  23. Factors Affecting The Design • Pavement slopes • Aggregate gradation • Porosity and effective porosity • Layer saturation • Permeability

  24. SR Sx LR W ( ) 0 . 5 = + LR 2 2 S S S S R x A W 0.5 2 æ ö S S = + ç ÷ LR W 1 è ø SX SR A SX è æ S Tan ( A ) ç ç = SX æ è Pavement Slopes

  25. Pavement Slopes • Surface and subsurface slopes • Always positive SR • Recommended slopes: • 0.02 m/m (normal conditions) • 0.025 m/m (high rainfall)

  26. Time-to-Drain Calculation t = T x m x 24 m-factor (days) Time factor Time to drain (hrs)

  27. Sl = LRSr/H Time to drain t = T x m x 24 where, t = time to drain in hours T = Time Factor m = “m” factor

  28. How to Estimate Time to Drain (t) • Input: • S and Sx • W, H, k, gd, Gsb, WL (for permeable base) • Interim Output: • SR, LR, S1 {S1 = (LR x SR)/H} • T for a desirable degree of drainage (U) • N and Ne • N = [1- {gd / (9.81 x Gsb)}] • Ne = N x WL • “m” factor: m = (Ne x LR2) / (k x H) • Output: t = T x m x 24 Transmissivity

  29. Time-to-Drain Sensitivity • Factors affecting time-to-drain: • Effective porosity • Coefficient of permeability • Resultant slope • Resultant length • Permeable base thickness

  30. Effect of k 6 LR = 7.6 m H = 0.15 m U = 50% SR = 0.02 m/m 4 Time to Drain, hrs 2 0 305 610 915 1220 Coefficient of Permeability, m/day

  31. Effect of SR 1 LR = 7.6 m H = 0.15 m U = 50% Ne = 0.25 k = 915 m/day .8 .6 Time to Drain, hrs .4 .2 0 .02 .04 .06 Resultant Slope, m/m

  32. Effect of LR 2 SR = 0.02 m/m H = 0.15 m U = 50% Ne = 0.25 k = 915 m/day 1 Time to Drain, hrs 0 3.6 7.2 10.8 14.4 Resultant Length, m

  33. Effect of Thickness 1.5 SR = 0.02 m/m U = 50% Ne = 0.25 m/m k = 915 m/day LR = 7.6 m 1 Time to Drain, hrs .5 0 100 200 300 Permeable Base Thickness, mm

  34. T for U = 50% Drained 7 5 3 Slope Factor (S1) 2 1 0 .01 .03 .10 .30 .60 Time Factor (T50)

  35. RoaDrainTM Time to Drain • Case B - Beneath Pavement • Time to Drain < 10 min • Case A - Beneath Subbase • for 15 in subbase with k = 1 ft/day • Time to drain ~ 3 hours

  36. Wisconsin DOT, Highway 60

  37. GPR Survey

  38. Conclusions • The RoaDrainTM geocomposite drainage layer is an effective alternative for pavement drainage. • Calculations based on time-to drain approach indicate: • adequate infiltration rates to handle significant storm events. • < 10 min. to drain the geocomposite layer. • < 2 hours hours to drain the road even when placed beneath moderately permeable dense graded aggregate base. • i.e. excellent drainage based on AASHTO 1998 criteria. • Five case studies in progress with 3 monitored study showing: • Excellent to good drainage following major storm events. • Geocomposite drains in subgrade found most effective, especially during spring thaw. • Geocomposite drains facilitated construction and may have improved roadway section stiffness. • FEM study shows good potential for Strain Energy Absorption

  39. QUESTIONS ? www.roadrainage.com

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