2CONTENTS OF PRESENTATION Water in Pavement SystemsConventional Drainage SolutionsGeocomposite Drainage Layer SolutionsDrainage Requirements for Permeable LayerGeocomposite Drainage EffectivenessCost BenefitsCase Histories
4Related ReferencesFHWA, 1992, Demonstration project 87: “Drainable pavement systems”, Participant Notebook, FHWA-SAUS Army Corps of Engineers, 1992, “Engineering and design drainage layers for pavements”, Engineer Technical Letter, , Department of Army.Cedergren, 1987, “Drainage of highway and airfield pavements”, R. E. Krieger publishing Co, FLChristopher and McGuffey, 1997, NCHRP Synthesis of highway practice 239, “Pavement subsurface drainage systems”, Transportation Research Board.Christopher, Hayden, and Zhao, 1999, “Roadway Base and Subgrade Geocomposite Drainage Layers, “ ASTM STP 1390, American Society for Testing and Materials, June.Christopher and Zhao, 2001, “Design manual for roadway geocomposite underdrain systems”, Tenax Corporation.
511/30/1998Standing water in a pavement indicates low permeability and poor drainage
6Under traffic loading, water and base material squirting up through joint in PCC pavement
7Water in Pavement Systems AASHTO (1993) reports:Water in the asphalt surfaceMoisture damage, modulus reduction and loss of tensile strengthSaturation reduces dry modulus of the asphalt 30 %Moisture in unbound aggregate base and subbaseLoss of stiffness 50 %Water in asphalt-treated baseModulus reduction of up to 30 percentIncrease erosion susceptibility of cement or lime treated basesSaturated fine grained roadbed soilModulus reductions 50 %AASHTO Guide for Design of Pavement Structures, 1993
8Severity factor measures the relative damage between wet and dry periodsFor 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.
9AASHTO Drainage Definitions 11/30/1998AASHTO Drainage DefinitionsQuality of DrainageExcellentGoodFairPoorVery PoorWater Removed Within*2 Hours1 Day1 Week1 MonthWater will not Drain*Based on time to drainAASHTO Guide for Design of Pavement Structures, 1993
10Design for Drainage (AASHTO, 1993 Design Method) Structural Number (SN) for a pavement section is:SN = a1*d1 + a2*d2*m2 + a3*d3*m3a1 a2 a3 = layer coefficients for AC, BC and Sub base layersd1, d2, d3 = their thicknessm2, m3 = drainage coefficients for the base and sub base layer
11Recommended Drainage Coefficient, cd, for Rigid Pavements 11/30/1998Recommended Drainage Coefficient, cd, for Rigid PavementsAASHTO Guide for Design of Pavement Structures, 1993
12By, Barry Christopher, Ph.D., P.E. and Aigen Zhao , Ph.D., P.E. Recommended values for drainage modifier, mi, for untreated base and subbase materials in flexible pavements (AASHTO, 1993).Quality ofDrainagePercent of time pavement is exposed to moisture levels approachingsaturationLess than 1%1 to 5%5 to 25%More than 25%Excellent1.20Good1.00Fair0.80Poor0.60Very Poor0.40Page. 6 Table 2 - from the Design Manual for Roadway Geocomposite Underdrain SystemsBy, Barry Christopher, Ph.D., P.E. and Aigen Zhao , Ph.D., P.E.
13Components of a Drainable Pavement 11/30/1998Components of a Drainable PavementChristopher and McGuffey, 1997, NCHRP Synthesis 239, “Pavement subsurface drainage systems”
14Time to Drain For two lane road - Lane width = 24 ft, Slope = 0.01 Base k time to drain QualityOGB ft/day 2 hrs to drain ExcellentDGAB ft/day 1 week FairDGAB w/ fines 0.1 ft/day 1 month PoorReality no drains does not drain Very Poor
15TRADEOFF OF STABILITY AND DRAINABILITY OF OGBC “Although the benefits of well-drained pavements have been clearly shown, there has always been hesitancy on the part of practitioners to use open-graded base courses because of concerns regarding a lack of stability of the open-graded layer….There is doubt as to how long the hydraulic conductivity of open-graded bases can be maintained because of upward migration of subgrade soil particles into the layer, as well as, possibly, the infiltration of fine particles from fractures in the pavement surface….”TRB Committee A2K06 on Subsurface Drainage Research Proposal for NCHRP“STABILITY AND DRAINABILITY OF OPEN-GRADED BASE COURSES”
17New Alternative Drainage Material: Geocomposite Drainage Layers 11/30/1998New Alternative Drainage Material: Geocomposite Drainage LayersMaine DOT
18Uses of Horizontal Geocomposite Drainage Layers 11/30/1998Uses of Horizontal Geocomposite Drainage Layers
19Separation between new asphalt overlay and subbase Tri-Planar RoaDrain Geocomposite to Replace Drainable Aggregate in Flexible Pavement SystemsAsphalt PavementExcellent DrainageEnhanced design lifeEnergy absorbing to mitigate reflective cracks from the existing PCC baseSeparation between new asphalt overlay and subbase
20Geocomposite to Replace Drainable Aggregate in Rigid or Flexible Pavement Systems DrainageFor Rigid PavementsExcellent drainageImproved Design> Cd
21Enhance Drainage of Dense Graded Base by Shortening Drainage Distance Improved Pavement Design> m or Cd> SNSeparationImproved long term performanceStabilizationImproved constructionReinforcementImproved Load Support
22Geocomposite Drain Requirements 11/30/1998Geocomposite Drain RequirementsSufficiently high inflow permeability to allow uninhibited flow from the adjacent pavement section during any major rainfall eventSufficient stiffness to support traffic without significant deformation under dynamic loadingSufficient transmissivity to rapidly drain the pavement section and prevent saturation of the baseSufficient air void exist within the geocomposite to provide a capillary breakChristopher, Hayden, and Zhao, “Roadway Base and Subgrade Geocomposite Drainage Layers, “ASTM STP 1390, American Society for Testing and Materials, June,1999.
23RoaDrainTM – Important Properties High TransmissivityCreep Resistance under High LoadsLong-term Resistance to CompressionStability Traffic Loads = Univ. of Illinois StudyA Void-Maintaining StructureGeotextile Filtration Requirements
24Fatigue Test Setup and Representative Results (Univ. Of Il Fatigue Test Setup and Representative Results (Univ. Of Il. Advanced Transportation Research and Engineering Lab)11/30/1998
26By, Barry Christopher, Ph.D., P.E. and Aigen Zhao , Ph.D., P.E. Comparison of drainage performance with and without RoaDrain geocomposite drainage net.RoaDrain onlyBase drainage onlyRoaDrainunder baseResultant slope0.021Resultant length24 feet24ThicknessEffective porosity0.690.15Transmissivity4500ResultsSlope factor:0.48M:0.08886Time to drain (hours):8400.86Page. 21 Table 3 - from the Design Manual for Roadway Geocomposite Underdrain SystemsBy, Barry Christopher, Ph.D., P.E. and Aigen Zhao , Ph.D., P.E.
27Equivalency of RoaDrain to 4” OGBL – flow capacity 4”- OGBL with (k =1000 – 3000 ft/day) transmissivity = ft3/day/ftFlow = 6 – 20 ft3/day/ftRoaDrain Synthetic Drainable Base Layer (SDBL) transmissivity = 1500 and 2% after considering an equivalency factor between geocomposite drain and soil drain.Flow = 30 ft3/day/ftSDBL > OGBL
28Frost Heave & RoaDrain as a Capillary Barrier 11/30/1998Frost Heave & RoaDrain as a Capillary BarrierFrost heave refers to the raising of a surface due to the formation of ice lenses in the underlying soil.
29Solutions to Reduce Frost Damage 11/30/1998Solutions to Reduce Frost DamageU.S. Army Corps of Engineers (1963):Limit the amount of frost-susceptible soil subjected to freezing temperatures.Design of adequate bearing capacity during the most critical climatic perioda significant increase in aggregate thickness
30Solutions to Reduce Frost Damage – RoaDrain Capillary Break 11/30/1998Solutions to Reduce Frost Damage – RoaDrain Capillary BreakPavementNon-frost susceptible baseFrost penetration depthNo this kind of ice lensFrost susceptible soilRoaDrain Capillary BarrierWater tableCapillary break must be placed between the ground water table and frost penetration depthIn addition to capillary rise, water flow to the freezing front is caused by an up-moving gradient related to temperature and pressure changes
31Freezing did not cause any observable physical changes US Army Cold Regions Research and Engineering Lab (CRREL) Study Concluded:RoaDrain was a very effective capillary barrier and eliminated frost heave in specimens from the Maine DOT test siteFreezing did not cause any observable physical changesHenry and Affleck, “Freezing tests on lean clay with Tenax tri-planar geocomposite as capillary barrier”
32Maine DOT Field Study Frankfort–Winterport Route 1A
43RoaDrain – Good to Excellent Drainage Discharge during the first year of monitoringcorresponds strongly with precipitation events andwater table levels. Based on the AASHTO definitionsfor pavement drainage capacity , the quality ofdrainage in the RoaDrain test section is good toexcellent.
4411/30/1998Falling Weight Deflectometer (FWD) Results (Drainage Sections), Maine DOTThe control section has a higher SN because it has 2-ft extra base filldue to poor subgrade conditions
5111/30/1998ConclusionsThe geocomposite drainage layer appears to be 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.Four case studies in progress with 1 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.