Axle load

Most of the modern truck engines are capable of hauling much heavier loads than the legal upper limit. Therefore the truck owners and operators have a tendency to overload these trucks enabling them to get more returns for the same investment and manpower. One of the major factors affecting pavement life is the magnitude and frequency of the wheel load repetitions imposed on the pavement structure. In order to maintain the heavy gross vehicle weight and still stay within the legal axle load limits, the trucking industry has devised the multiple axle configurations, which include rear tandem axle trucks. It is observed from the study, that the percentage of overloading of commercial vehicles is very high, which result in greater extent of damage to the pavement, thus reducing the serviceable life of pavement. From analysis, it is observed that the rate of the growth of deterioration is less when enforcement is implied. It implies that there is necessary to strengthen the pavements much earlier with the present trend of overloading when compared with the enforcement situation, wherein the tandem axles / equivalent standard axle trucks are used to reduce the overloading effect .In the present study, Ahmadabad ring road about 76 km one of the major traffic corridors has been considered to assess the effect of overloading on the design and performance of pavement.

Degradation and axial deformations of railway ballast bed are highly influenced by stresses induced by moving trains. Hence, this study evaluate the influence of train axle load on the rate of degradation and axial deformation of railway ballast bed. Series of cyclic loading test were conducted at intervals of 200,000 load cycles up to 1,000,000 cycles. Two trains with capacities of 30 ton and 24 tons for freight and passengers respectively were simulated at a typical moving speed of 120 km/hr which is equivalent to a frequency of 16.5 Hz. It was observed that with an increase in both axle load and number of load cycles, the degradation index and the axial deformation increased. It was also observed that ballast degradation has a strong influence on the ballast bed deformation. Hence, ballast degradation is highly influenced by train axle load and the axial deformation of the ballast bed has a strong correlation with the rate of ballast particles degradations

The new FHWA Mechanistic–Empirical Pavement Design Guide (M-E PDG) does away with the AASHO-derived concept of the equivalent single-axle load and calculates damage caused by various axle configurations directly. Because multiple axles represent about half the axle configurations that the pavement will experience, there is a need to evaluate the M-E PDG procedure for predicting rutting due to multiple-axle configurations. Axle factors (AFs) based on rutting were calculated for different axle configurations by using three procedures: the M-E PDG, accounting for the effect of each individual axle within a group, and integrating the entire strain pulse. The AFs from these procedures were compared with laboratory-derived values for asphalt concrete. Also, layer rutting contributions were predicted for six in-service SPS-1 experiment sections from the Long-Term Pavement Performance Program with the M-E PDG software and were compared with the analysis of their transverse surface profiles....