The Effect of Axle Overloading and High Tire Pressure on Flexible Pavement Structure

Abstract

Axle overloading and high tire pressures on the highways and motorways in Pakistan are one of the reasons that cause early pavement deterioration. There are numerous sections on the national highway on which trucks are reposted to be operating at 40-80 percent higher tire pressure than the legal limit, and the axle overloading is 30 percent greater than the legal axle load limit. This research aims at determining the effect of axle overloading and high tire pressure on the flexible pavement structure and derive the truck factors for trucks in order to quantify the damage to the pavement due to a single pass of 2-axle, 3-axle, 4-axle, 5-axle, and 6-axle truck using the results reported in the Pilot Axle Load Survey conducted by the National Transport Research Centre. In order to determine the effect of axle overloading and high tire pressure, a theoretical linear elastic mechanistic empirical analysis for different axle configurations was performed using KENLAYER and regression models were developed to find the Equivalent Axle Load Factor (EALFs) for the fatigue cracking, and permanent deformation. It was found that the EALFs were mostly controlled by permanent deformation distress criterion. The EALFs and the truck factors were highly influenced by the axle loads rather than the tire pressure. The 3-axle truck was found to be the most damaging truck followed by 6-axle truck, 5-axle truck, 2- axle truck, and 4-axle truck.