Drainage and Maintenance – The Way to Preserve Pavements
Pavement Premature Failure
“60% of all premature failures are caused by drainage problems.”
-ASHTO
Pavement Structure
Pavement Response to Load
What Water Does
Reduces Stiffness by:
Effect Of Stiffness on Pavement Response
Fatigue Failure
Sub grade Rutting
Potholing and Collapse
Potholes
Potholes
Water Sources
Mostly from Surface!
Base and Subgrade Drainage
Surface
“60% of all premature failures are caused by drainage problems.”
-ASHTO
Pavement Structure
Pavement Response to Load
What Water Does
Reduces Stiffness by:- Increased pore pressures that lower internal friction and thus shear resistance
- Buoyancy of particles that reduce effective weight and lowers inter particle friction.
- Expansive soils cause differential heave.
- Frost heave due to freezing and thawing of the pavement.
Effect Of Stiffness on Pavement Response
Fatigue Failure
Sub grade Rutting
Potholing and Collapse
Potholes
Potholes
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Water Sources
Mostly from Surface!
- Cracks joints
- Adjoining impermeable areas
- Runoff
- Blocked, cracked drains
- No drainage
- Wrong slopes
Designing for Moisture
- Rainfall and evaporation
- Permeability of surface
- Water table
- Permeability of pavement layers
- Shoulders
- Type
- Seepage from higher ground
- Infiltration
- Freeze Thaw
- Positive Pore Pressure
- Sensitivity of sub grade soils to moisture
Base and Subgrade Drainage
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Surface
- Most Water comes from the surface
- Cracks, holes, seepage from higher ground
Base
- Permeability
- Slope, width
- Free draining preferable
- High density base with asphalt treatment or HMA
- Protect by adequate surface drainage and integrity
Surface
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Sub Surface
- Can cause a layer of mud at base subgrade interface.
- Depends on composition- volume change
- Compaction
Sub grade Drainage
Sources:
- Ground water
- Surface water
- Longitudinal drains
- Soil assessment
- Water flows
- Freeze thaw
- Drain materials
Problem Correction
- Dig Outs
- Sealing
- Install sub surface drains
- Assess changes in area use and adjacent area use for drainage.
- Keep existing drains clear
- Correct elevations do not over pave
Rehabilitation Strategies
- Preventing damage
- Maintenance
- Pot hole and crack repair
- Surfacing and Sealing
- Slurry
- Chip Seal
- Hot Mix Patching and overlay
- Asphalt Rubber Membranes
- Cape Seal
- Geo-textiles
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Geotextile
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Geotextile
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Conclusions
- Many pavement failures are due to drainage problems
- These are either due to poor design or changes during the life of the pavement
- Most problems are surface related so preventative maintenance and proper rehabilitation is the key
Last Updated (Monday, 14 December 2009 15:48)