Analysis of Fatigue and Rutting Behavior of Flexible Pavement: A Case Study of Taudaha-Pharping Road

Flexible pavements are widely used in Nepal due to their adaptability; however, they are prone to distress, such as fatigue cracking and rutting, which reduces their service life. This study evaluates the fatigue and rutting behavior of the Taudaha-Pharping road section through pavement condition surveys, traffic analysis, mechanistic-empirical evaluation using KENPAVE, and expert interviews. The Pavement Condition Index (PCI) was employed to assess surface distress. At the same time, traffic data and material properties were analyzed to compute cumulative Equivalent Single Axle Loads (ESALs) and stress-strain responses. Field surveys revealed that 65% of the pavement was in excellent condition (PCI≥85), while 9% was in failed condition (PCI<10), highlighting immediate rehabilitation works in these sections. Traffic analysis forecasted a 10.15 million standard axle load (MSA) over a 10-year design period. KENPAVE simulations and calculations using the Department of Roads (DoR) guidelines indicated that the pavement could withstand 10.98 MSA (fatigue life) and 18.49 MSA (rutting life), exceeding the projected traffic demand, suggesting that wheel load alone does not fully explain the observed fatigue and rutting distress. Expert interviews further validated that poor drainage, insufficient compaction, and material deficiencies triggered the observed distress. The study concludes that while the structural design is adequate, preventive maintenance is required for distressed sections. The findings support the adoption of KENPAVE for pavement analysis in Nepal and highlight the importance of material quality and proper drainage in extending pavement lifespan.