pavement design

FLEXIBLE PAVEMENT OVERLAY DESIGN
DEFLECTION OF PAVEMENT SECTION
IN ADDITION TO THE SEASONAL VARIATIONS, THE DEFLECTION OF A PAVEMENT
SECTION MAY VARY ALONG ITS LENGTH. TO REDUCE THE EFFECT OF BOTH
VARIABLES, A STATISTICAL PROCESS IS USED WHEN ESTIMATING THE MAXIMUM
DEFLECTION.
• DIVIDE THE PAVEMENT INTO SECTIONS WHICH ARE 300M LONG. THE SECTIONS CAN BE
OF VARIABLE LENGTH PROVIDED THEY ARE HOMOGENEOUS WITH RESPECT TO THE
FACTORS WHICH INFLUENCE THE PAVEMENT DESIGN (E.G., SUBGRADE AND TRAFFIC)
• SELECT AT LEAST 10 STRATIFIED TEST POINTS WITHIN EACH SECTION USING A TABLE
OF RANDOM NUMBERS
• OBTAIN THE DEFLECTION MEASUREMENT AT THE SELECTED TEST POINTS USING THE
FALLING WEIGHT DEFLECTOMETER
• CALCULATE THE AVERAGE DEFLECTION (X) AND THE STANDARD DEVIATION (σ x
)
• CALCULATE THE ESTIMATED MAXIMUM PROBABLE DEFLECTION VALUE
D max = ( X + 2σ x )
WATCH FOR OUTLIERS (LOCAL REPAIR), ADJUST FOR SEASON, SPRING ~ 1.5 x FALL,
CONVERT TO STATIC (BENKELMAN BEAM EQUIVALENT), BENKELMAN BEAM ~ 1.5 X FWD