Influence of tire pressure on the rutting and fatigue life of bituminous pavement

In India, the axle loads have increased substantially in the recent decades and a majority of such overloaded vehicles are expected to have increased tire pressure. Increased tire pressures have a significant impact on the performance of the pavement as the load is applied over a concentrated area. Very little data is available related to the magnitude of tire pressures currently observed in India and its impact on the rutting (Nr) and fatigue (Nf) life of bituminous pavements. This study aims at quantifying such information for India. A field survey was conducted at five weighbridges for 100 vehicles to measure the tire pressures and the corresponding axle loads. Considering all the rear axles, it was observed that the mean tire pressure was 833 kPa and about 50% of the vehicles operated with a tire pressure greater than 800 kPa. To illustrate the combined influence of axle load and tire pressure, pavement sections available in IRC: 37-2018 were chosen and evaluated for their rutting and fatigue performance. For instance, for 10% CBR and 50 Million Standard Axles (MSA) traffic, when the tire pressure was increased from 500 kPa to 1200 kPa, it was observed that Nf reduced by 41% and Nr reduced by 5%. The fatigue life of the surface layer is seen to be more sensitive to variation in tire pressure. Moreover, the magnitude of influence exerted by the tire pressure depended on the axle load to a large extent.