Effects of flexible pavement design parameters on pavement performance

Pavements deteriorate over time when exposed to traffic and environment. Improving pavement performance at the design stage is the simplest and most cost-effective approach in optimally managing pavements. The research aim to study how the choice of design parameters can increase pavements life by evaluating the effects of several input parameters TO pavement design on pavement performance. The research will also determine the input parameters and their use in order to improve the performance of pavement. Three types of pavement structures most commonly used most commonly used Tanzania were analyzed, namely pavement type I - asphalt concrete on granular base, pavement type Il - asphalt concrete on bituminous base and pavement type Ill - asphalt concrete on cemented base. The subbases for all three structures were made of granular material resting on subgrade soil. In the analysis, axle load. tyre pressure using Elastic Layer Systerm-5 (ELSYM5-) program to calculate strains and South Africa performance models to determine pavement lives. Another approach involved the use of High way Development and Management (HDM-4) deterioration model to determine pavement performance. Results show that for ELSYM5 approach, the parameters that mostly influenced fatigue performance are the tyre pressure, base modulus, Aphalt concrete (AC) thickness and axle load for pavement type I ; axle load, base thickness and AC thickness have largest influence on pavement types types II largest and for pavement type lll most -sensitive parameters were base thickness, axle load, base modulus and AC thickness. For HDM-4 approach, the input parameters that mostly affected pavement performance in terms of fatigue cracking are AC thickness, upgrade modulus and base thickness for pavement type I and Il: and AC thickness, subgrade modulus and base modulus for pavement type Ill. Since variation employed in input parameters using South Africa performance models together with ELSYM5 on the one hand and HDM-4 model on the other hand are what could be found as possible variation for existing parameters in Tanzania. It is recommended that the design input parameters found to have great influence on pavement performance be more accurately determined as well as constructed.