session 4 drainage design considerations. objectives identify types of subsurface drainage ...
TRANSCRIPT
SESSION 4SESSION 4SESSION 4SESSION 4
Drainage Design Drainage Design ConsiderationsConsiderations
Drainage Design Drainage Design ConsiderationsConsiderations
ObjectivesObjectives
Identify types of subsurface drainageIdentify types of subsurface drainage
Determine need for subsurface Determine need for subsurface drainagedrainage
Recognize importance of maintenanceRecognize importance of maintenance
Identify surface drainage design Identify surface drainage design factorsfactors
IntroductionIntroduction
Moisture is a major cause of distressMoisture is a major cause of distress
Drainage long recognized as key Drainage long recognized as key design considerationdesign consideration
Focus on drainage of surface Focus on drainage of surface infiltration waterinfiltration water
Effect of DrainageEffect of Drainage
Moisture-Related Moisture-Related DistressesDistresses
Moisture-Related Moisture-Related DistressesDistresses
Moisture-Related Moisture-Related DistressesDistresses
Moisture-Related Moisture-Related DistressesDistresses
Approaches to Approaches to Drainage ProblemsDrainage Problems
Seal the pavementSeal the pavement
Use moisture-insensitive materialsUse moisture-insensitive materials
Install subsurface drainageInstall subsurface drainage
Types of Subsurface Types of Subsurface DrainageDrainage
Daylighted basesDaylighted bases
Longitudinal edge drain systemLongitudinal edge drain system
Drainable pavement systemDrainable pavement system
DaylightedDaylighted
Subgrade
PCC Slab
Agg. Base
Shoulder
Aggregate Base CarriedOut to Ditchline
Shoulder
Aggregate Base CarriedOut to Ditchline
Traffic LaneTraffic Lane
Longitudinal Edge Longitudinal Edge Drain SystemDrain System
SlopeSlope Slope
Inner Shoulder Traveled Way Outer Shoulder
TPM
FilterFabric
Base (LCB, ACB)
Filter Fabric, High Side ofTangents and Superelevations
PCC PCCPPCCP PCC
California California DesignDesign
Example Drainable Example Drainable Pavement SystemPavement System
AC Shoulder
GeotextileAggregate Separator Layer Permeable
Base
Geotextile
AC Shoulder
PCC Mainline
Components of a Components of a Drainable Pavement Drainable Pavement SystemSystem Permeable basePermeable base
Separator layerSeparator layer
Longitudinal collector pipeLongitudinal collector pipe
Permeable BasePermeable Base
Permeability of 300 to Permeability of 300 to 3,000 m/day (1,000 to 3,000 m/day (1,000 to 10,000 ft/day)10,000 ft/day)
100 to150 mm (4 to 6 100 to150 mm (4 to 6 in) thickin) thick
Treated or untreatedTreated or untreated
Separator LayerSeparator Layer
Prevent intrusion of fines into Prevent intrusion of fines into permeable basepermeable base
Dense-graded aggregateDense-graded aggregate
GeotextileGeotextile
Longitudinal Collector Longitudinal Collector PipePipe Collects water and outlets to ditchesCollects water and outlets to ditches
Typically 100 to 150 mm (4 to 6 in) Typically 100 to 150 mm (4 to 6 in) corrugated plastic pipecorrugated plastic pipe
Outlet spacing 76 to 150 m (250 to Outlet spacing 76 to 150 m (250 to 500 ft)500 ft)
Design and Analysis of Design and Analysis of Drainage SystemsDrainage Systems DefineDefine
Material propertiesMaterial properties Roadway/pavement geometricsRoadway/pavement geometrics Climatic dataClimatic data
Determine inflow/outflow characteristicsDetermine inflow/outflow characteristics
Determine drainage requirementsDetermine drainage requirements
Consideration of Consideration of Drainage in Slab Drainage in Slab Thickness DesignThickness Design
AASHTO Drainage CoefficientAASHTO Drainage Coefficient
Drainage , Thickness Drainage , Thickness
Reduction in properties of paving Reduction in properties of paving materialsmaterials
Determining Need for Determining Need for Subsurface DrainageSubsurface Drainage Available free moistureAvailable free moisture
Material propertiesMaterial properties
Cross sectional designCross sectional design
Subgrade drainabilitySubgrade drainability
Traffic levelsTraffic levels
< 3.0 None
3.0 - 6.0 None/EDS None None None
> 6.0 EDS/DPS
NCHRP 1-32NCHRP 1-32Drainage GuidelinesDrainage Guidelines
EDS = Longitudinal Edge Drain SystemDPS = Drainable Pavement System
WET CLIMATE DRY CLIMATE ESALs, Weak Strong Weak Strong millions Subgrade Subgrade Subgrade Subgrade
Inclusion ofInclusion ofSubsurface DrainageSubsurface Drainage Local experienceLocal experience
Past performancePast performance
Cost effectivenessCost effectiveness
Construction and maintenance Construction and maintenance practicespractices
Maintenance of Maintenance of Drainage InstallationsDrainage Installations Ensures functionality of drainage systemEnsures functionality of drainage system Often a “forgotten” maintenance itemOften a “forgotten” maintenance item Activities include:Activities include:
Reference markersReference markers Cleaning outletsCleaning outlets Flushing/rodding edge drainsFlushing/rodding edge drains Cleaning/reestablishing ditchesCleaning/reestablishing ditches Periodic video inspectionPeriodic video inspection
Video Inspection of Video Inspection of Edge DrainsEdge Drains
Crushed Pipe and Silt Crushed Pipe and Silt BuildupBuildup
Unwanted Unwanted InhabitantsInhabitants
Surface Drainage Surface Drainage ConsiderationsConsiderations Pavement cross slope (tangent section)Pavement cross slope (tangent section)
2% recommended2% recommended Shoulder cross slopeShoulder cross slope
3% recommended3% recommended DitchesDitches
Width: 0.9 to 1.2 m (3 to 4 ft)Width: 0.9 to 1.2 m (3 to 4 ft) Depth: 1.2 m (4 ft) beneath pavement Depth: 1.2 m (4 ft) beneath pavement
Grade: 1%Grade: 1%
SummarySummary
Moisture-related distressesMoisture-related distresses
Subsurface drainage typesSubsurface drainage types
Determining need for subsurface Determining need for subsurface drainagedrainage
Maintenance considerationsMaintenance considerations
Surface drainage considerationsSurface drainage considerations