| A newly constructed portion of the National Highway (N5) between Hyderabad and Karachi, Pakistan, showed signs of pavement distress and failure as a result of heavy rainfall and hail storm soon after it was opened to traffic in April 1994. The National Highway Authority (NHA), decided to perform a pavement investigation which included nondestructive falling weight deflectometer (FWD) tests and test pits for material characteristics and quality control. The data from FWD tests was used for mechanistic evaluation of pavement layers using the MICHBACK and MICHPAVE computer programs. The statistical analysis of the NDT data and the backcalculated layer moduli using the MICHBACK computer program showed considerable variations along the length of the road. These variations in the deflection data and the layer moduli can be attributed to construction practices and, perhaps, to poor quality control. These layer moduli and the pavement layer thicknesses were then used to determine the remaining service life of various pavement sections and required overlay thicknesses to improve the structural capacity of the pavement using the MICHPAVE computer program and the Asphalt Institute method. It can be concluded from this study that parts of the National Highway N5 were severely underdesigned. |
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