Environmental Factors Affecting Pavement Design

Include various climatic factors affecting the flexible and rigid pavements such as variation in moisture content, frost action, variation in temperature etc.

1. Environmental Factors
Affecting Pavement Design
VijaiKrishnan V
M.TechStudent
RIT Kottayam

2. Factors affecting pavement design
Wheel load
Subgrade soil
Pavement component materials
Climatic and Environmental Factors
Drainage

3. Climatic Factors
Variation in moisture condition
Frost action
Variation in temparature

4. Variation in Moisture Content
Depends on
1.Climatic conditions
2.Fluctuations of ground water level
3.Type of soil
4.Drainage conditions
5.Type of pavement and shoulders

5. RainSurface water enter subgrade through pavement
or its edge
Capillary action in subgrade soil also affect moisture
content
High plasticity soil volume vary with variation in water
content

6. Differential rise or fall of pavement edges subgrade
moisture content below centre is different from that at
pavement edge
Stabilityof subgrade decrease due to adverse moisture
conditions –progressive andcumulative damage to
pavement

7. High moisture variation –controlled by surfaceand
subsurface drainagesystem
Poor drainage Reduce shear strength
Pumping in rigid pavements

8. Frost Action
Overall effect due to frost heave, frost melting and alternate
freeze-thaw cycle
Frost Heave
During winter
Held water in subgrade form ice crystals at freezing temperature
Size of crystal increase raise a portion of pavement
Non-uniform heaving cause damage

9. Frost Melting
During spring/summer
Increase in temperature result in melting or thawing of frozen crystals
soften subgrade/road bed
Decrease load bearing capacity due to voids created by
melting
Excessive deflection under heavy traffic progressive failure

11. Frost action depends on :-
Soil -type, GSD, density, permeability and capillarity
Temperature below freezing point and its duration
Supply of water –capillarity or soil suction
Type and colour of pavement
Freeze-thaw damage
on flexibilepavement

12. Frost action prevention :-
Proper surface and subsurface drainage
Sufficient thickness for each layer
Use non-frost susceptible material –clean sand, gravel
Capillary cutoff –granular or bituminous layer, geotextile
Soil stabilization
Mix CaCl
2and NaClwith soil –lower freezing temperature

13. Variation in Temperature
Daily and seasonal variation
Affect design, performance and life of pavement
Flexible Pavement
Hot weather bitumen binder softens
Very cold weatherbitumen stiffens or become brittle
Affect resilient modulus of surface course
Rigid Pavement
Temperatureor frictional stresses are developed